Strain Mapping of Single Nanowires using Nano X-ray Diffraction

Nanowires are explored as basic components for a large range of electronic devices. The nanowire format offersseveral benefits, including reduced material consumption and increased potential for combining materials to formnew novel heterostructures. Several factors, such as mechanical stress from contacting or a lattice mismatch in aheterostructure, can strain and change the lattice tilt. The strain is often intertwined with small gradients ofcomposition. The strain relaxation can differ significantly from bulk due to the small diameters, but the mechanismsare not fully comprehended. X-rays have a penetrating power that makes it possible to investigate embeddedsamples without preparation or slicing. The high flux of coherent X-ray beams from synchrotron radiation facilities,combined with the nano-focus capabilities developed in recent years, have made it possible to probe nano-crystals.The 4th generation of synchrotrons, including MAX IV in Lund, Sweden, has even higher brilliance than previoussources. Diffraction imaging techniques using synchrotron radiation can reveal small strains down to 10-4-10-5. Thefield of coherent imaging pushes the limits of resolutions below the size of the focus. With Bragg ptychography, thedisplacement field in a crystal can be probed with resolution beyond the probe focus by numerically reconstructingthe phase.This thesis includes the development of X-ray nano-diffraction methods for the characterizing of nanowires, includingGaInP/InP barcode nanowires, p-i-n InP nanowire devices and metal halide perovskite CsPbBr3 nanowires. Itincludes a theoretical background of the scattering mechanisms in Thomson scattering in nano-crystals, goesthrough the formalism for coherent diffraction imaging, crystal structure and deformation in nanoobjects and thetechnical aspects of the experimental setup and measurement. Moreover, theoretical modelling of elastic strainrelaxation in these nanowires was performed with finite element modelling.Single III-V nanowire heterostructures and III-V nanowire devices were probed with scanning XRD and Braggprojection ptychography (BPP). How the techniques compare to each other and how the results are affected by thedifferent approximations that are made in the respective technique was explored. Finite element simulationscombined with nano-diffraction revealed that the lattice mismatch of 1.5% could be relaxed elastically for thediameter of 180 nm. From the strain mapping of the nanowire device, we found how the contacting of the nanowirebends the nanowire resulting in a tilt normal to the substrate.Single perovskite metal-halide perovskite CsPb(Br(1-x)Clx)3 nanowire heterostructures were characterized withscanning nano-XRD and XRF, which showed that the lattice spacing was affected by composition and strain.Composition gradients revealed that Cl diffusion had taken place within the heterostructure. Furthermore, extractingthe lattice tilts from shifts of the Bragg peak revealed a ferroelastic domain structure with simultaneously existinglattice tilts. These findings are beneficial for the further development of MHP nanowires devices

The cooked and the raw

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68786/2/10.1177_016555158200400506.pd

Thermopower simulation of a two level spinless quantum dot

Quantum dots are interesting candidates for a broad variety of electronic components, with single electron transistors and LEDs being two examples already well on their way. In nanostructures, such as quantum dots, quantum effects greatly influence the transport. In a spin polarized quantum dot system with two energy levels, interference effects have been found to cause a strong suppression of conductance [Phys. Rev. Lett. 104, 186804 (2010)]. In the present work, this system is further investigated with thermopower acting as probing tool. Thermopower is a measure of the voltage induced by a temperature difference, attributed to the Seebeck effect, at vanishing current. While conductance probes transport at and around the Fermi level, thermopower does so for a wider range of energies. For the system addressed in this work, thermopower is evaluated as a probing tool complementary to conduction. To simulate transport, a generalized master equation approach is used; the second order von Neumann approach. This method takes into account second order tunneling as well as interference effects; coherence and correlations. The simulations show that the conductance suppression manifest itself also in the thermopower and furthermore, with a more prominent signal

Controlled drinking : a viable treatment goal in alcohol use disorder?

Alcohol use disorders (AUD) has one of the largest treatment gaps among psychiatric diagnoses, with a treatment coverage of 10 to 20 %. One of the key contributing factors is the lack of treatments aiming for controlled drinking (CD) instead of abstinence. Although a large number of trials investigated CD as the outcome, there are major limitations to the existing studies, such as small sample sizes, non-adequate control conditions, and heterogenous definitions of CD outcomes. Further, very few studies have investigated clinically relevant predictors of outcomes specifically in CD in sufficiently large sample sizes. Efficacy studies have been the main focus in research on CD and very few studies have investigated patient perspectives on the treatments offered for a CD goal. Lastly, there are few validated clinically relevant measures for the assessment and evaluation of impaired control over alcohol consumption, which is predictive of outcome in treatment for controlled drinking. The primary aim of the thesis was to investigate if a CD goal was viable in a treatment seeking sample of individuals of patients with AUD. This aim was broken down in the four following studies. Study I was a randomized controlled superiority trial including 250 individuals with alcohol use disorder. We hypothesized that Behavioral Self-Control Training (BSCT), a five-session cognitive and behavioral treatment, would be superior to Motivational Enhancement Therapy (MET), which was a four-session treatment based on Motivational Interviewing in reducing weekly alcohol consumption. Linear mixed models were used to analyze primary and secondary outcomes alongside with a Bayes factor analysis for the primary outcome. No differences were identified between groups for the primary outcome of mean weekly alcohol consumption at 26 weeks (primary endpoint). The secondary outcome proportion of weeks with hazardous drinking defined in line with the former Swedish low-risk drinking recommendations of >9/>14 weekly standard drinks was found to be statistically different between groups. Study II was a prospective cohort study, in which we investigated differences at 52 weeks post inclusion between BSCT and MET for both alcohol consumption and related consequences as well as predictors of treatment outcome. Linear and logistic mixed regression models were used for the outcomes at 52 weeks, and linear and logistic regression models for the predictor analyses. BSCT was superior to MET for the change between baseline to 52 weeks for the outcome of CD, which was defined as drinking levels in line with the new low-risk drinking levels of less than10.0 weekly standard drinks per week for both women and men(p=0.048). In the sample altogether, 50.5 % succeeded with a CD level at 52 weeks. A total of 57 % of individuals in BSCT attained a level of CD, as opposed to 43 % in MET, which was a statistically significant difference. The clinical characteristics in individuals with CD levels compared to those not attaining a CD goal showed that there were substantial differences om clinically relevant outcomes, such as quality of life and reduction of risk and harm, favoring those with CD. Further, Study II showed that predictors for obtaining CD and reducing weekly alcohol consumption was a lower baseline alcohol consumption. Predictors of symptom reduction in AUD were lower severity of AUD at baseline and a lower self-rated impaired control over alcohol consumption. Women were also found be significantly more successful in attaining CD, at both 12, and 52 weeks post inclusion. In conclusion, the study suggested that females and receiving BSCT was more favorable for attaining a long-term goal of CD. Baseline levels of AUD, baseline consumption and impaired control were corroborated as predictors of outcome. Study III was a qualitative interview study with the aim to investigate how patients experienced MET as their treatment for AUD and a goal of controlled drinking. Fifteen patients (8/7 female/male) were recruited at the 26-week follow-up. Interview data was analyzed with thematic analysis. Five themes were identified: the therapist conveyed the MI-spirit, the therapist did not guide on how to reach the goal, participants were committed to change before starting treatment, participants were uncertain if treatment was enough to maintain change, and significant others were not wanted in sessions. One conclusion from this study was that there may be a need for modification of the MET manual, to support some patients in attaining a CD goal. The format may need to be prolonged to support patients sense of self-efficacy to change. Lastly, significant others were important for the support of change without necessarily being present in sessions. Study IV was a psychometric study which evaluated the psychometric properties of the Swedish version of the Impaired control scale. We aimed to investigate dimensionality, reliability, convergent and divergent validity, measurement invariance and sensitivity to change for the evaluation of psychometric properties. The analyses of dimensionality by a principal component analysis of Rasch residuals indicated some multidimensionality created by two items (12, 22) (I can stop/ I would be able to stop/ before getting completely drunk). Tests of convergent and divergent validity showed that failed control had the strongest associations to impaired control and alcohol use disorder while the attempted control part was not associated with the construct of impaired control or alcohol use disorder. The conclusion from this study was that the failed control scale was the most valid measure of impaired control, and was sensitive to change when measured again post treatment. This makes the ICS (except the attempted control subscale) suitable as an assessment- and treatment evaluation instrument in AUD treatment of drinking. The main conclusions of the thesis were that CD was a viable goal to the majority of individuals in a sample of treatment-seeking individuals with AUD with a low level of psychiatric comorbidity, one year after receiving psychological treatment aiming for CD. When comparing outcomes on alcohol- and related consequences as well as quality of life, individuals with a CD level showed more favorable outcomes than those who were not at this consumption level. Baseline alcohol consumption was corroborated as a key predictor of outcome in treatment for CD, for the outcomes of CD and mean weekly consumption, while AUD severity and impaired control were corroborated for the prediction of reduction of AUD symptoms. Although not proven to be superior for the primary outcome, there was supporting evidence that patients who received BSCT were shown to attain a CD level in more cases both at 12 weeks and at the one-year follow-up. Further, women were far more successful in attaining a CD goal. In order to increase self-efficacy to change in patients receiving MET, the manual may need modification on how to adapt treatment to a CD goal, as well as delivering MET in more flexible format. Lastly, the Swedish version of the Impaired control scale (except the attempted control subscale) can be used in health care settings and in research for the assessment and evaluation of treatment for CD

Aspects of common mental disorders in primary care

Depression and anxiety disorders are common in the general population. Primary care is the first line of care for people with common mental disorders. This doctoral project investigated aspects of common mental disorders, including diagnostic procedures and interventions in primary care. Study I was an observational study of 480 people in the regions of Stockholm and Västra Götaland on sick leave for common mental disorders. It used structured psychiatric interviews (M.I.N.I.) and symptom severity scales (MADRS-S, KEDS) to investigate the relationship between sick leave certificate diagnoses for common mental disorders and diagnoses made in the psychiatric interviews. It also examined length of sick leave by diagnoses on certificates, interview diagnoses, and symptom severity. Many participants fulfilled the criteria for mental disorders other than the sick leave certificate diagnosis. For example, 76% on sick leave for stress-induced exhaustion disorder (SED) and 67% on sick leave for anxiety disorder fulfilled the criteria for depression (p=0.041). Diagnoses on certificates were not associated with sick leave length. Fulfilling SED criteria was associated with longer sick leave (144 vs. 84 days, p<0.001), as were more severe symptoms. Thus, sick leave certificate diagnoses do not reflect the diagnoses obtained in structured psychiatric interviews. This could mirror the changing and overlapping nature of the symptoms of common mental disorders and suggests that findings based on sick leave certificate diagnoses should be interpreted with caution. The association between longer sick leave and more severe symptoms or fulfilling SED criteria is clinically relevant and worth further study. Study II used data from the PRIM-CARE cluster randomized controlled trial (RCT) at 23 primary care centers (11 intervention, 12 control) in Västra Götaland and Dalarna to compare the 12- and 24-month effectiveness of care managers to usual care for primary care patients with depression (n=376: 192 intervention, 184 control). Patients with care managers had less severe symptoms (MADRS-S, p=0.02) and higher quality of life (EQ-5D, p=0.01) at 12 months. Improvements in patients without care managers meant that this was no longer the case at 24 months (MADRS-S, p=0.83, EQ-5D, p=0.88). Responses to a study-specific postal questionnaire at 24 months showed that patients with care managers were more confident that they could get information (53% vs 38%; p=0.02) and professional emotional support (51% vs 40%; p=0.05). Care managers for primary care patients with depression therefore seem superior to usual care in the long term, as it took up to 24 months for patients without care managers to achieve the same improvements as patients with care managers achieved in 6 months and maintained long-term. Moreover, patients with care managers had more confidence in future care. Study III explored the views and experiences of general practitioners (GPs) who worked with the care managers in the PRIM-CARE study to better understand the GPs’ perspectives on this organizational change. Transcripts from five focus-group discussions with GPs were analyzed with qualitative content analysis. GPs thought care managers could ensure care quality while freeing GPs from case management. They could also feel concern about role overlap, think that care managers should be assigned to patients who need them the most, and express the belief that transition to a chronic care model required change. In summary, GPs could see benefits to assigning care managers to patients with depression. However, they expressed concern about role overlap and emphasized the need to clarify care managers’ role in the care team. Study IV was an RCT pilot trial that investigated the feasibility and effectiveness of two cognitive behavioral therapy (CBT) protocols for generalized anxiety disorder (GAD) in primary care, intolerance-of-uncertainty therapy (IUT) and meta-cognitive therapy (MCT). Feasibility measures included recruitment, drop-out, patients’ perceptions of participation and treatment, and therapists’ competence in and adherence to protocol. Effectiveness measures, assessed at pre-treatment, post-treatment, and 6 months, included worry, depressive symptoms, functional impairment, and quality of life. The recruitment process was smooth, dropout was low, and patients were satisfied with treatment (scale 0-6, median 5.17, SD 1.09). Therapists’ competence and adherence to protocol were rated weak to mediocre. Both therapies effectively reduced worry with large effect sizes (Cohen’s d IUT = -2.69, 95% confidence interval [-3.63, -1.76] and Cohen’s d MCT = -3.78 [-4.68, -2.90]). MCT resulted in statistically superior improvements (d = -2.03 [-3.31, -0.75]). Results were maintained at 6 months. It is thus feasible to conduct an RCT comparing IUT and MCT in primary care patients with GAD. Both treatments effectively reduce worry, but MCT seems superior. A full-scale RCT is required to confirm these findings

A comparison of DFT and SVD based channel estimation in MIMO OFDM systems

In this paper two simplified transform based estimators for MIMO OFDM systems using the DFT and an SVD based transform are compared over a tapped delay line channel model. In the resulting symbol error rate plots, it is seen that the DFT based estimator experiences an error floor caused by the mismatch between the discrete time model and a continuous time reality. This error floor becomes a problem at high SNR levels where high data-rate systems can be expected to operate. When using an SVD based estimator it is seen that this error floor is reduced at the cost of a somewhat increased estimator complexit