Solcore: A multi-scale, python-based library for modelling solar cells and semiconductor materials

Computational models can provide significant insight into the operation mechanisms and deficiencies of photovoltaic solar cells. Solcore is a modular set of computational tools, written in Python 3, for the design and simulation of photovoltaic solar cells. Calculations can be performed on ideal, thermodynamic limiting behaviour, through to fitting experimentally accessible parameters such as dark and light IV curves and luminescence. Uniquely, it combines a complete semiconductor solver capable of modelling the optical and electrical properties of a wide range of solar cells, from quantum well devices to multi-junction solar cells. The model is a multi-scale simulation accounting for nanoscale phenomena such as the quantum confinement effects of semiconductor nanostructures, to micron level propagation of light through to the overall performance of solar arrays, including the modelling of the spectral irradiance based on atmospheric conditions. In this article we summarize the capabilities in addition to providing the physical insight and mathematical formulation behind the software with the purpose of serving as both a research and teaching tool.Comment: 25 pages, 18 figures, Journal of Computational Electronics (2018

Pediatric advance care planning from the perspective of health care professionals: a qualitative interview study.

BACKGROUND: Pediatric advance care planning differs from the adult setting in several aspects, including patients' diagnoses, minor age, and questionable capacity to consent. So far, research has largely neglected the professionals' perspective. AIM: We aimed to investigate the attitudes and needs of health care professionals with regard to pediatric advance care planning. DESIGN: This is a qualitative interview study with experts in pediatric end-of-life care. A qualitative content analysis was performed. SETTING/PARTICIPANTS: We conducted 17 semi-structured interviews with health care professionals caring for severely ill children/adolescents, from different professions, care settings, and institutions. RESULTS: Perceived problems with pediatric advance care planning relate to professionals' discomfort and uncertainty regarding end-of-life decisions and advance directives. Conflicts may arise between physicians and non-medical care providers because both avoid taking responsibility for treatment limitations according to a minor's advance directive. Nevertheless, pediatric advance care planning is perceived as helpful by providing an action plan for everyone and ensuring that patient/parent wishes are respected. Important requirements for pediatric advance care planning were identified as follows: repeated discussions and shared decision-making with the family, a qualified facilitator who ensures continuity throughout the whole process, multi-professional conferences, as well as professional education on advance care planning. CONCLUSION: Despite a perceived need for pediatric advance care planning, several barriers to its implementation were identified. The results remain to be verified in a larger cohort of health care professionals. Future research should focus on developing and testing strategies for overcoming the existing barriers

"Hope for the best, prepare for the worst": A qualitative interview study on parents' needs and fears in pediatric advance care planning.

Pediatric advance care planning is advocated by healthcare providers because it may increase the chance that patient and/or parent wishes are respected and thus improve end-of-life care. However, since end-of-life decisions for children are particularly difficult and charged with emotions, physicians are often afraid of addressing pediatric advance care planning. We aimed to investigate parents' views and needs regarding pediatric advance care planning. We performed a qualitative interview study with parents of children who had died from a severe illness. The interviews were analyzed by descriptive and evaluation coding according to Saldaña. We conducted semi-structured interviews with 11 parents of 9 children. Maximum variation was sought regarding the child's illness, age at death, care setting, and parent gender. Parents find it difficult to engage in pediatric advance care planning but consider it important. They argue for a sensitive, individualized, and gradual approach. Hope and quality of life issues are primary. Parents have many non-medical concerns that they want to discuss. Written advance directives are considered less important, but medical emergency plans are viewed as necessary in particular cases. Continuity of care and information should be improved through regular pediatric advance care planning meetings with the various care providers. Parents emphasize the importance of a continuous contact person to facilitate pediatric advance care planning. Despite a need for pediatric advance care planning, it is perceived as challenging. Needs-adjusted content and process and continuity of communication should be a main focus in pediatric advance care planning. Future research should focus on strategies that facilitate parent engagement in pediatric advance care planning to increase the benefit for the families

Medical indication regarding life-sustaining treatment for children: Focus groups with clinicians.

Decisions about medical indication are a relevant problem in pediatrics. Difficulties arise from the high prognostic uncertainty, the decisional incapacity of many children, the importance of the family, and conflicts with parents. The objectivity of judgments about medical indication has been questioned. Yet, little is known about the factors pediatricians actually include in their decisions. Our aims were to investigate which factors pediatricians apply in deciding about medical indication, and how they manage conflicts with parents. We performed a qualitative focus group study with experienced pediatricians. The transcripts were subjected to qualitative content analysis. We conducted three focus groups with pediatricians from different specialties caring for severely ill children/adolescents. They discussed life-sustaining treatment in two case scenarios that varied according to diagnosis, age, and gender. The decisions about medical indication were based on considerations relating to the individual patient, to the family, and to other patients. Individual patient factors included clinical aspects and benefit-burden considerations. Physicians' individual views and feelings influenced their decision-making. Different factors were applied or weighed differently in the two cases. In case of conflict with parents, physicians preferred solutions aimed at establishing consensus. The pediatricians defined medical indication on a case-by-case basis and were influenced by emotional reasoning. In contrast to prevailing ethico-legal principles, they included the interests of other persons in their decisions. Decision-making strategies should incorporate explicit discussions of social aspects and physicians' feelings to improve the transparency of the decision-making process and reduce bias

Mode-hop-free tuning over 135 GHz of external cavity diode lasers without anti-reflection coating

We report an external cavity diode laser (ECDL), using a diode whose front facet is not antireflection (AR) coated, that has a mode-hop-free (MHF) tuning range greater than 135 GHz. We achieved this using a short external cavity and by simultaneously tuning the internal and external modes of the laser. We find that the precise location of the pivot point of the grating in our laser is less critical than commonly believed. The general applicability of the method, combined with the compact portable mechanical and electronic design, makes it well suited for both research and industrial applications.Comment: 5 pages, 5 figure

A Laser System for the Spectroscopy of Highly-Charged Bismuth Ions

We present and characterize a laser system for the spectroscopy on highly-charged ^209Bi^82+ ions at a wavelength of 243.87 nm. For absolute frequency stabilization, the laser system is locked to a near-infra-red laser stabilized to a rubidium transition line using a transfer cavity based locking scheme. Tuning of the output frequency with high precision is achieved via a tunable rf offset lock. A sample-and-hold technique gives an extended tuning range of several THz in the UV. This scheme is universally applicable to the stabilization of laser systems at wavelengths not directly accessible to atomic or molecular resonances. We determine the frequency accuracy of the laser system using Doppler-free absorption spectroscopy of Te_2 vapour at 488 nm. Scaled to the target wavelength of 244 nm, we achieve a frequency uncertainty of \sigma_{244nm} = 6.14 MHz (one standard deviation) over six days of operation.Comment: Contribution to the special issue on "Trapped Ions" in "Applied Physics B