Coherent inverse Compton scattering with attosecond electron bunches accelerated and compressed by radially polarized laser pulses

We present a study of direct laser driven electron acceleration and scaling of attosecond bunch compression in unbound vacuum. Simple analytical expressions and detailed three-dimensional numerical calculations including space charge reveal the conditions for compression to attosecond electron sheets. Intermediate emittance minima suitable for brilliant x-ray generation via coherent inverse Compton scattering (ICS) are predicted. We verify the coherent emission properties of the resulting x-ray fields and demonstrate feasability for realistic laser parameters.Comment: 4 pages, 4 figure

Elimination of periodic nonlinearities of actuators with internal periodic processes

We discuss an algorithm that eliminates the periodic non-linearity of a bimorph piezo actuator by modifying the phase of the voltage waveforms used for driving the actuator. The procedure presented allows for a separate optimization of the motion of the actuator groups in order to obtain the properties desired (such as a specific stepsize or maximum force). The resulting response of a bimorph piezo drive, also under different loads, is experimentally investigated. The optimization process can be applied to other actuators relying on internal periodic processes, if the motion is reproducible, and is limited by measurement noise or manufacturing tolerances only

Understanding the user experience of customer service chatbots: What can we learn from customer satisfaction surveys?

Understanding and improving user experience is key to strengthening uptake and realizing the potential of chatbots for customer service. In this paper, we investigate customer satisfaction surveys as a source of insight into such user experience. A total of 5,687 customer satisfaction reports on users’ interactions with a customer service chatbot, and the corresponding chatbot interactions, are analyzed. The findings demonstrate that customer satisfaction reports are closely associated with the degree to which the problems motivating users’ chatbot interactions are resolved. Furthermore, the findings show substantial variation in the performance of different chatbot intents in terms of customer satisfaction and problem resolution. This implies that user experience varies substantially depending on the problems motivating users to interact with the chatbot. Finally, we identify key characteristics of the intents associated with particularly high or low customer experience, suggesting paths towards efficient improvement of chatbot user experience. Based on the findings, we point to key implications for theory and practice and suggest directions for future research.acceptedVersio

Galaxies Probing Galaxies at High Resolution: Co-Rotating Gas Associated with a Milky Way Analog at z=0.4

We present results on gas flows in the halo of a Milky Way-like galaxy at z=0.413 based on high-resolution spectroscopy of a background galaxy. This is the first study of circumgalactic gas at high spectral resolution towards an extended background source (i.e., a galaxy rather than a quasar). Using longslit spectroscopy of the foreground galaxy, we observe spatially extended H alpha emission with circular rotation velocity v=270 km/s. Using echelle spectroscopy of the background galaxy, we detect Mg II and Fe II absorption lines at impact parameter rho=27 kpc that are blueshifted from systemic in the sense of the foreground galaxy's rotation. The strongest absorber EW(2796) = 0.90 A has an estimated column density (N_H>10^19 cm-2) and line-of-sight velocity dispersion (sigma=17 km/s) that are consistent with the observed properties of extended H I disks in the local universe. Our analysis of the rotation curve also suggests that this r=30 kpc gaseous disk is warped with respect to the stellar disk. In addition, we detect two weak Mg II absorbers in the halo with small velocity dispersions (sigma<10 km/s). While the exact geometry is unclear, one component is consistent with an extraplanar gas cloud near the disk-halo interface that is co-rotating with the disk, and the other is consistent with a tidal feature similar to the Magellanic Stream. We can place lower limits on the cloud sizes (l>0.4 kpc) for these absorbers given the extended nature of the background source. We discuss the implications of these results for models of the geometry and kinematics of gas in the circumgalactic medium.Comment: 14 pages, 6 figures, submitted to ApJ, comments welcom

Why Did They Come Here? - The Influences and Expectations of First-Year Students’ College Experience

Students’ expectations and experiences with university life are influenced by a number of variables. Many universities develop programs or promote aspects of existing programs to market the university’s image. This research was motivated by our desire to determine the relationships between first-year students’ college expectations and experiences, their awareness of the university’s programming and projected image, the influence of the programming and image on their decision to attend the institution, and the students’ personal characteristics. Our survey of 351 first-year students revealed positive perceptions of their university expectations and experiences, a mixture of influences on their decision to attend the university, and correlations between program awareness and the influence on students’ university attendance. We also uncovered a number of relationships between expectations, experience, and perceptions of influences with the personal characteristics of the students. Implications, directions for future research, and limitations are discussed

How to select interventions for promoting physical activity in schools? Combining preferences of stakeholders and scientists

Background The failure to scale-up and implement physical activity (PA) interventions in real world contexts, which were previously successful under controlled conditions, may be attributed to the different criteria of stakeholders and scientists in the selection process of available interventions. Therefore, the aim of our study was to investigate and compare the criteria applied by local stakeholders and scientists for selecting amongst suitable school-based PA interventions for implementation. Methods We conducted a three-round repeated survey Delphi study with local stakeholders (n = 7; Bremen, Germany) and international scientific PA experts (n = 6). Independently for both panels, two rounds were utilized to develop a list of criteria and the definitions of criteria, followed by a prioritization of the criteria in the third round. For each panel, a narrative analysis was used to rank-order unique criteria, list the number of scorers for the unique criteria and synthesize criteria into overarching categories. Results The stakeholders developed a list of 53 unique criteria, synthesized into 11 categories with top-ranked criteria being ‘free of costs’, ‘longevity’ and ‘integration into everyday school life’. The scientists listed 35 unique criteria, synthesized into 7 categories with the top-ranked criteria being ‘efficacy’, ‘potential for reach’ and ‘feasibility’. The top ranked unique criteria in the stakeholder panel were distributed over many categories, whereas four out of the top six criteria in the scientist panel were related to ‘evidence’. Conclusions Although stakeholders and scientists identified similar criteria, major differences were disclosed in the prioritization of the criteria. We recommend an early collaboration of stakeholders and scientists in the design, implementation, and evaluation of PA interventions

Prioritizing cleft/craniofacial surgical care after the COVID-19 pandemic

Background: It is anticipated that in due course the burden of emergency care due to COVID-19 infected patients will reduce sufficiently to permit elective surgical procedures to recommence. Prioritizing cleft/craniofacial surgery in the already overloaded medical system will then become an issue. The European Cleft Palate Craniofacial Association, together with the European Cleft and Craniofacial Initiative for Equality in Care, performed a brief survey to capture a current snapshot during a rapidly evolving pandemic. Methods: A questionnaire was sent to the 2242 participants who attended 1 of 3 recent international cleft/craniofacial meetings. Results: The respondents indicated that children with Robin sequence who were not responding to nonsurgical options should be treated as emergency cases. Over 70% of the respondents indicated that palate repair should be performed before the age of 15 months, an additional 22% stating the same be performed by 18 months. Placement of middle ear tubes, primary cleft lip surgery, alveolar bone grafting, and velopharyngeal insufficiency surgery also need prioritization. Children with craniofacial conditions such as craniosynostosis and increased intracranial pressure need immediate care, whilst children with craniosynostosis and associated obstructive sleep apnea syndrome or proptosis need surgical care within 3 months of the typical timing. Craniosynostosis without signs of increased intracranial pressure needs correction before the age of 18 months. Conclusions: This survey indicates several areas of cleft and craniofacial conditions that need prioritization, but also certain areas where intervention is less urgent. We acknowledge that there will be differences in the post COVID-19 response according to circumstances and policies in individual countries

Hydrogen Epoch of Reionization Array (HERA)

The Hydrogen Epoch of Reionization Array (HERA) is a staged experiment to measure 21 cm emission from the primordial intergalactic medium (IGM) throughout cosmic reionization ($z=6-12$), and to explore earlier epochs of our Cosmic Dawn ($z\sim30$). During these epochs, early stars and black holes heated and ionized the IGM, introducing fluctuations in 21 cm emission. HERA is designed to characterize the evolution of the 21 cm power spectrum to constrain the timing and morphology of reionization, the properties of the first galaxies, the evolution of large-scale structure, and the early sources of heating. The full HERA instrument will be a 350-element interferometer in South Africa consisting of 14-m parabolic dishes observing from 50 to 250 MHz. Currently, 19 dishes have been deployed on site and the next 18 are under construction. HERA has been designated as an SKA Precursor instrument. In this paper, we summarize HERA's scientific context and provide forecasts for its key science results. After reviewing the current state of the art in foreground mitigation, we use the delay-spectrum technique to motivate high-level performance requirements for the HERA instrument. Next, we present the HERA instrument design, along with the subsystem specifications that ensure that HERA meets its performance requirements. Finally, we summarize the schedule and status of the project. We conclude by suggesting that, given the realities of foreground contamination, current-generation 21 cm instruments are approaching their sensitivity limits. HERA is designed to bring both the sensitivity and the precision to deliver its primary science on the basis of proven foreground filtering techniques, while developing new subtraction techniques to unlock new capabilities. The result will be a major step toward realizing the widely recognized scientific potential of 21 cm cosmology.Comment: 26 pages, 24 figures, 2 table

Asexuality: Classification and characterization

This is a post-print version of the article. The official published version can be obtaineed at the link below.The term “asexual” has been defined in many different ways and asexuality has received very little research attention. In a small qualitative study (N = 4), individuals who self-identified as asexual were interviewed to help formulate hypotheses for a larger study. The second larger study was an online survey drawn from a convenience sample designed to better characterize asexuality and to test predictors of asexual identity. A convenience sample of 1,146 individuals (N = 41 self-identified asexual) completed online questionnaires assessing sexual history, sexual inhibition and excitation, sexual desire, and an open-response questionnaire concerning asexual identity. Asexuals reported significantly less desire for sex with a partner, lower sexual arousability, and lower sexual excitation but did not differ consistently from non-asexuals in their sexual inhibition scores or their desire to masturbate. Content analyses supported the idea that low sexual desire is the primary feature predicting asexual identity