Thermionic emission current in a single barrier varactor

From I-V measurements on Single Barrier Varactors (SBV) at different temperatures we concluded that thermionic emission across the barrier of the actual device is mainly due to transport through the X band. The same structure was also modeled with a one-dimensional drift-diffusion model, including a 'boundary condition' for thermionic emission across the heterojunction interface. By including thermionic field emission through the top of the triangular barrier of a biased diode and the effect of a non-abrupt interface at the heterojunction, we obtained good agreement between the modeled and measured I-V characteristics

Pre-analytical errors in blood sampling procedures in paediatric hospital care

Introduction Blood tests are important for diagnosing and treating children who are hospitalised with illnesses. The blood test process follows the specific phases of pre-analysis, analysis and post-analysis. Most blood test errors occur in the pre-analytical phase. Such pre-analytical errors (PAE) can affect children’s safety due to delayed clinical decision-making support or discomfort related to repeated blood sampling. Aim The overall research aim of this doctoral thesis was to investigate the frequency and consequences of PAE in paediatric hospital care. In specific, the following research questions were set out to be answered: • How frequent is PAE? • Which type of blood sampling methods, capillary or venous, is most affected by PAE? • What are the annual costs associated with blood tests affected by PAE? • What are nurses’ experiences with blood sampling procedures and related PAE? Methods Information about how frequently PAE occurs was retrieved from the laboratory information system FlexLab™, which contained data from blood analyses ordered from Astrid Lindgren Children’s Hospital from 2013 to 2014. Information on the type of blood sampling method and associated PAE factors was retrieved from a blood sampling survey and the medical record Take Care™. The costs associated with blood tests affected by PAE were calculated using hospital information from combined data sources and supply systems (Flexlab™, Tableau softwareÓ and Medicarrier AB). Clinical observations were also used to estimate the time healthcare personnel spend on the blood sampling process. A qualitative approach was used to explore the participating nurses’ views and experiences with PAE and with the blood sampling process. Results The frequency of PAE was 61,656 (5.4%) of 1,148,716 blood analyses sent to the laboratory from Astrid Lindgren Children’s Hospital (2013-2014). Clotting represented 31,605 (51.3%) of all PAE. Based on 951 blood samples from two paediatric inward departments, the capillary sampling method had a significantly higher risk of PAE than venous blood sampling, at 72 (20%) of 354 vs 56 (9.4%) of 597, p = 0.001, adj-OR 2.88 (CI 1.79-4.64). The annual cost of PAE was estimated at approximately 84,000 euros. The highest expense was personnel cost (65%), which amounted to 55,000 euros annually. Focus group interviews demonstrated that blood sampling was a challenge for nurses, revealing that they need more information about how to reduce PAE. Conclusion The results of this thesis demonstrate that the high frequency of PAE is primarily related to clotting. Capillary blood sampling carries a higher risk of PAE than venous blood sampling. The consequences of PAE include substantial annual costs to paediatric hospital care. Nurses need both theoretical and practical training on how to avoid PAE when conducting capillary and venous samplin

Progress on single barrier varactors for submillimeter wave power generation

Theoretical work on Single Barrier Varactor (SBV) diodes, indicate that the efficiency for a multiplier has a maximum for a considerably smaller capacitance variation than previously thought. The theoretical calculations are performed, both with a simple theoretical model and a complete computer simulation using the method of harmonic balance. Modeling of the SBV is carried out in two steps. First, the semiconductor transport equations are solved simultaneously using a finite difference scheme in one dimension. Secondly, the calculated I-V, and C-V characteristics are input to a multiplier simulator which calculates the optimum impedances, and output powers at the frequencies of interest. Multiple barrier varactors can also be modeled in this way. Several examples on how to design the semiconductor layers to obtain certain characteristics are given. The calculated conversion efficiencies of the modeled structures, in a multiplier circuit, are also presented. Computer simulations for a case study of a 750 GHz multiplier show that InAs diodes perform favorably compared to GaAs diodes. InAs and InGaAs SBV diodes have been fabricated and their current vs. voltage characteristics are presented. In the InAs diode, was the large bandgap semiconductor AlSb used as barrier. The InGaAs diode was grown lattice matched to an InP substrate with InAlAs as a barrier material. The current density is greatly reduced for these two material combinations, compared to that of GaAs/AlGaAs SBV diodes. GaAs based diodes can be biased to higher voltages than InAs diodes

Students’ own collective criteria - influence on peer feedback and lab report quality

SHORT SUMMARYWhat happens when you let the students collectively decide together what’s meant by “good quality” for example in a lab report? Will this adequately guide their own learning as shown by their written lab reports and peer feedback comments? Or is it better to just tell them what you expect?ABSTRACTIntended audience:This presentation will likely mostly interest teachers who use or want to start using peer review in their courses (at bachelor or master level). Teachers of courses with lab report assignments may also be interested in my example of use of peer feedback in this learning context.Problem statement:Many students, at the onset of advanced level studies at Chalmers, lack the ability to produce a good quality lab report. Such generic skills are expected to be in place before students leave Chalmers with their master’s degree. Experience has shown that “just” telling the students how to write a good report is not sufficient. Might they listen more to each other than to the teacher?Suggested solution:If students are collectively given the chance to spell out what they mean by a “good quality” lab report, agreeing upon a list of criteria in class, this list can be used to guide their learning through applying their own criteria. This list of criteria can support their individual first draft writing process, as well as their individual feedback given to each other in a structured peer review process. Finally, the feedback given by the teacher can reference the students’ own list of criteria when making the final assessment of the revised report. Chosen learning scenarios:This method has been applied for two consecutive years in an introductory course within the MPWPS program. An introductory lecture before labs start includes a collective exercise where students provide their take on quality criteria for lab reports. The teacher takes the role of secretary, creating their collective list on the whiteboard, and making the list available in PingPong after the lecture. (See Ref. 1.) If key aspects are being forgotten by the students collectively during the process, the teacher can drop gentle hints in order to have the final quality criteria list quality assured.Seven obligatory short labs are performed in pairs, but only one of these labs is individually and randomly assigned to each student for writing a formal lab report. Students are then assigned peer review roles, and apply these quality criteria to a report on a different lab by another student. Revised lab reports are then submitted, along with a short text on how the peer feedback was incorporated into the final version. With peer review of first drafts, the reviewer as well as the author of the report will be learning during the process, while carefully applying the quality criteria.During the two most recent years, when the above system was in place in this course, the teaching differed in one significant way: the most recent year included a lecture dedicated to academic honesty and the avoidance of plagiarism. (See Ref. 2.) In previous years, quality criteria were provided by the teacher, not by the collective group of students. (See Ref. 3.)Student achievement measures:We analyze the student achievements (lab report quality) as a measure of their learning in three different aspects: core subject content learning, generic written communication skills, and academic honesty. The latter analysis is reported in a separate presentation (Ref. 2.) The generic written communication skills will be the focus of my presentation, with an attempt at measuring the degree to which the student’s own quality criteria list was actually successfully applied in their lab report and peer review writing. It will however not be possible to make a “fair and scientific” comparison to previous years’ student lab reports, since other factors were also changed at the same time.\ua0Comparison of resulting achievement for different scenarios:Student learning connected to similar quality criteria will be compared for the “student collectively generated” criteria (the latest two years of the course) and the “teacher generated” criteria (provided previously). The two different years this student generated criteria scenario was used had slightly different criteria lists – which may or may not be evident in the outcome of the students’ writing. This course has just finished, and the analysis will be performed during the coming study period before the KUL conference, so results are pending.Alternative solutions:In a more traditional scenario, the teacher informs the students of the quality criteria, set by the teacher, and the teacher applies the criteria when grading the assignment. Both comments and grades are usually provided by the teacher to individual students, who sometimes resubmit assignments after taking into account the teacher-provided feedback. However, in many cases, the feedback comes without any further requirement posed, and therefore without strong incentives for further learning. Much research has been done on criteria based assessment including negotiating criteria with students, (see e.g. Ref. 4.) Here, however, I have just given my suggestion of one way of assessing, which I have found to work well\ua0\ua0References:1. ”Lab report quality criteria”, available on PingPong at the following link:\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 https://pingpong.chalmers.se/courseId/7038/content.do?id=3366624 \ua02. KUL 2017, Undervisa och examinera akademisk hederlighet, submitted ”short presentation”3. KUL 2012, Systematisk feedback och progression som st\uf6d f\uf6r studenters l\ue4rande inom generella kompetenser.4. Biggs, J. ”Teaching for quality Learning at University”, 2003, chapters 8 and 9

Undervisa och examinera akademisk hederlighet

KORT SAMMANFATTNINGVi har lagt in en obligatorisk f\uf6rel\ue4sning om Akademisk hederlighet, plagiering och otill\ue5tet samarbete i en av de inledande obligatoriska kurserna i mastersprogrammet MPWPS. F\ue4rdigheterna testas dels direkt med en quiz, men framf\uf6r allt genom en individuell skriftlig laborationsrapport.ABSTRACTAntalet anm\ue4lda fall av misst\ue4nkt plagiering vid h\uf6gskolorna \uf6kar i en betydligt h\uf6gre takt \ue4n andra former av anm\ue4lda disciplin\ue4renden (UK\uc4, 2014). Vad som avses med plagiering och hur man undviker det \ue4r dock inte sj\ue4lvklart. F\uf6r att kopiering ska bli otill\ue5ten i dessa sammanhang m\ue5ste den ha utf\uf6rts med avsikt att vilseleda under examination (Carroll och Zetterling, 2009). V\ue5ra erfarenheter fr\ue5n tidigare \ue5r visar att vi beh\uf6ver arbeta mer aktivt med begrepp som akademisk hederlighet och plagiering. Det har inte varit tillr\ue4ckligt att dela ut Chalmers policy kring akademisk hederlighet (Wennberg 2009) och en kort genomg\ue5ng vid mottagning av mastersstudenterna. I en av de obligatoriska kurserna i f\uf6rsta l\ue4sperioden p\ue5 mastersprogrammet Tr\ue5dl\uf6s Teknik, Fotonik och Rymdteknik har vi d\ue4rf\uf6r kombinerat en obligatorisk f\uf6rel\ue4sning kring akademisk hederlighet med inl\ue4mning av en individuell laborationsrapport. Under f\uf6rsta halvan av f\uf6rel\ue4sningen definierar vi plagiering, ser vad som st\ue5r i h\uf6gskolef\uf6rordningen, hur man skriver utifr\ue5n k\ue4llor, samt informerar om den hj\ue4lp Chalmers kan erbjuda vid rapportskrivning, t.ex. CHOCS och engelska-kurser. Under andra halvan av f\uf6rel\ue4sningen besvarar studenterna m.h.a. sina mobiler en quiz med \ue5tta olika p\ue5st\ue5enden kring plagiering och otill\ue5tet samarbete. Fr\ue5gorna \ue4r h\ue4mtade fr\ue5n Henriksson (2008). Vi avslutar med att g\ue5 igenom de olika p\ue5st\ue5endena tillsammans och tittar p\ue5 f\uf6rdelningen av korrekta och felaktiga svar. Inf\uf6r rapportskrivandet tilldelas varje student slumpm\ue4ssigt att skriva en mer utf\uf6rlig laborationsrapport kring en av de sju obligatoriska laborationsuppgifter som ing\ue5r i kursen. De skickar in ett utkast av rapporten till Ping Pong via Urkund. Studenterna ger sedan \ue5terkoppling p\ue5 varandras utkast, s.k. peer review. Studenterna tar med rekommendationerna som de f\ue5tt fr\ue5n peer review och l\ue4mnar sedan in en slutlig rapport till l\ue4rarna f\uf6r granskning. Kursen har precis avslutats, men vi kommer utv\ue4rdera effekten m.h.a. en tillagd fr\ue5ga i kursenk\ue4ten, och en j\ue4mf\uf6relse av f\uf6rekomsten av plagiat i \ue5rets och f\uf6reg\ue5ende \ue5rs rapporter.Anv\ue4nd litteraturCarroll, J.J., Zetterling C.M. (2009). Hj\ue4lp studenterna att undvika plagiering. Stockholm: Kungliga tekniska h\uf6gskolan.Henriksson, A.-S. (2008) Att f\uf6rebygga plagiat i studentarbeten – en pedagogisk utvecklingsm\uf6jlighet. Uppsala: Uppsala universitet.UK\uc4 rapport 2014:3, Disciplin\ue4renden 2013 vid universitet och h\uf6gskolor. Stockholm, Universitetskansler-\ue4mbetet.Wennberg. B. (2009) Akademisk hederlighet p\ue5 Chalmers – Vilka \ue4r v\ue5ra spelregler? G\uf6teborg: Chalmers tekniska h\uf6gskola

Identification of Vascularised Carotid Plaques Using a Standardised and Reproducible Technique to Measure Ultrasound Contrast Uptake

ObjectivesContrast-enhanced ultrasonography (CEUS) has been used to assess the vascularisation of carotid plaques. Our aim was to develop and validate a standardised semi-automated method for CEUS examination of plaques, and test if the technique could be used to identify vulnerable plaques.MethodsStudy participants were a mixed population of symptomatic and asymptomatic subjects, selected if they had a plaque with height >2.5 mm and <10% acoustic shadowing. Participants received a bolus of ultrasound contrast agent and a 90-s cine-loop was captured. A Contrast Quantification Program (CQP) was developed and trained to identify extent of contrast uptake after motion correction and application of a noise reduction algorithm. The technique was validated by comparing CQP values with visual assessment of contrast uptake. CQP values were also compared with plaque echogenicity and history of clinical events.ResultsCQP values correlated with a visual, 5-scale classification of contrast uptake by two blinded, experienced sonographers. Repeated contrast injections showed high reproducibility. Participants with a history of ipsilateral stroke/TIA had significantly higher CQP values than asymptomatic participants.ConclusionWe present a reproducible, semi-automatic method to identify vascularisation of carotid plaques, which could be used in prospective studies to determine the clinical value of plaque vascularisation

Semi-supervised learning with natural language processing for right ventricle classification in echocardiography - a scalable approach

We created a deep learning model, trained on text classified by natural language processing (NLP), to assess right ventricular (RV) size and function from echocardiographic images. We included 12,684 examinations with corresponding written reports for text classification. After manual annotation of 1489 reports, we trained an NLP model to classify the remaining 10,651 reports. A view classifier was developed to select the 4-chamber or RV-focused view from an echocardiographic examination (n\ua0=\ua0539). The final models were two image classification models trained on the predicted labels from the combined manual annotation and NLP models and the corresponding echocardiographic view to assess RV function (training set\ua0n\ua0=\ua011,008) and size (training set\ua0n\ua0=\ua09951. The text classifier identified impaired RV function with 99% sensitivity and 98% specificity and RV enlargement with 98% sensitivity and 98% specificity. The view classification model identified the 4-chamber view with 92% accuracy and the RV-focused view with 73% accuracy. The image classification models identified impaired RV function with 93% sensitivity and 72% specificity and an enlarged RV with 80% sensitivity and 85% specificity; agreement with the written reports was substantial (both κ\ua0=\ua00.65). Our findings show that models for automatic image assessment can be trained to classify RV size and function by using model-annotated data from written echocardiography reports. This pipeline for auto-annotation of the echocardiographic images, using a NLP model with medical reports as input, can be used to train an image-assessment model without manual annotation of images and enables fast and inexpensive expansion of the training dataset when needed