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1.
Best Pract Res Clin Rheumatol ; : 101939, 2024 Mar 14.
Article in English | MEDLINE | ID: mdl-38485601

ABSTRACT

Systemic Lupus Erythematosus (SLE) imposes a great burden on the lives of patients. Patients' and physicians' concerns about the disease diverge considerably. Physicians focus on controlling disease activity to prevent damage accrual, while patients focus on symptoms that impact on Health-Related Quality of Life (HRQoL). We explored the physicians' and patients' perspective and the potential role of Patient Reported Outcomes (PROs). Physicians are aware of the theoretical usefulness of PROs to collect information deriving from the patients' perspective. However, they often do not know how to interpret and use these questionnaires in a real shared therapeutic strategy. For the patients, it's important to be seen as a whole person with a true consideration of how they feel and function. Strategies to help bridge the communication gap could include: better use of time during visits, preparing for the consultation, a more understandable lay language used by the doctor, a dedicated nurse.

2.
Nat Rev Rheumatol ; 19(9): 592-602, 2023 09.
Article in English | MEDLINE | ID: mdl-37433880

ABSTRACT

Systemic lupus erythematosus (SLE) is a disease of high unmet therapeutic need. The challenge of accurately measuring clinically meaningful responses to treatment has hindered progress towards positive outcomes in SLE trials, impeding the approval of potential new therapies. Current primary end points used in SLE trials are based on legacy disease activity measures that were neither specifically designed for the clinical trial context, nor developed according to contemporary recommendations for clinical outcome assessments (COAs), such as that substantial patient input should be incorporated into their design. The Treatment Response Measure for SLE (TRM-SLE) Taskforce is a global collaboration of SLE clinician-academics, patients and patient representatives, industry partners and regulatory experts, established to realize the goal of developing a new COA for SLE clinical trials. The aim of this project is a novel COA designed specifically to measure treatment effects that are clinically meaningful to patients and clinicians, and intended for implementation in a trial end point that supports regulatory approval of novel therapeutic agents in SLE. This Consensus Statement reports the first outcomes of the TRM-SLE project, including a structured process for TRM-SLE development.


Subject(s)
Lupus Erythematosus, Systemic , Humans , Lupus Erythematosus, Systemic/diagnosis , Lupus Erythematosus, Systemic/drug therapy , Consensus , Outcome Assessment, Health Care
4.
Front Med (Lausanne) ; 9: 889997, 2022.
Article in English | MEDLINE | ID: mdl-36226147

ABSTRACT

Background: Patient registries play a crucial role in supporting clinical practice, healthcare planning and medical research, offering a real-world picture on rare and complex connective tissue diseases (rCTDs). ERN ReCONNET launched the first European Registry Infrastructure with the aim to plan, upgrade and link registries for rCTDs, with the final goal to promote a harmonized data collection approach all over Europe for rCTDs. Methods: An online survey addressed to healthcare professionals and patients' representatives active in the field of rCTDs was integrated by an extensive database search in order to build a mapping of existing registries for rCTDs. Findings: A total of 140 registries were found, 38 of which include multiple diseases. No disease-specific registry was identified for relapsing polychondritis, mixed connective tissue disease and undifferentiated connective tissue disease. Discussion: This overview on the existing registries for rCTDs provides a useful starting point to identify the gaps and the strengths of registries on the coverage of rCTDs, and to develop a common data set and data collection approach for the establishment of the TogethERN ReCONNET Infrastructure.

6.
Lupus Sci Med ; 9(1)2022 10.
Article in English | MEDLINE | ID: mdl-36283746

ABSTRACT

OBJECTIVE: We conducted an international survey of patients with SLE to assess their access, preference and trust in various health information sources pre-COVID-19 and during the COVID-19 pandemic. METHODS: Patients with SLE were recruited from 18 observational cohorts, and patients self-reporting SLE were recruited through five advocacy organisations. Respondents completed an online survey from June 2020 to December 2021 regarding the sources of health information they accessed in the 12 months preceding (pre-11 March 2020) and during (post-11 March 2020) the pandemic. Multivariable logistic regressions assessed factors associated with accessing news and social media post-11 March 2020, and self-reporting negative impacts from health information accessed through these sources. RESULTS: Surveys were completed by 2111 respondents; 92.8% were female, 76.6% had postsecondary education, mean (SD) age was 48.8 (14.0) years. Lupus specialists and family physicians were the most preferred sources pre-11 March 2020 and post-11 March 2020, yet were accessed less frequently (specialists: 78.5% pre vs 70.2% post, difference -8.3%, 95% CI -10.2% to -6.5%; family physicians: 57.1% pre vs 50.0% post, difference -7.1%, 95% CI -9.2% to -5.0%), while news (53.2% pre vs 62.1% post, difference 8.9%, 95% CI 6.7% to 11.0%) and social media (38.2% pre vs 40.6% post, difference 2.4%, 95% CI 0.7% to 4.2%) were accessed more frequently post-11 March 2020 vs pre-11 March 2020. 17.2% of respondents reported negative impacts from information accessed through news/social media. Those outside Canada, older respondents or with postsecondary education were more likely to access news media. Those in Asia, Latin America or younger respondents were more likely to access social media. Those in Asia, older respondents, males or with postsecondary education in Canada, Asia or the USA were less likely to be negatively impacted. CONCLUSIONS: Physicians, the most preferred and trusted sources, were accessed less frequently, while news and social media, less trusted sources, were accessed more frequently post-11 March 2020 vs pre-11 March 2020. Increasing accessibility to physicians, in person and virtually, may help reduce the consequences of accessing misinformation/disinformation.


Subject(s)
COVID-19 , Lupus Erythematosus, Systemic , Social Media , Male , Humans , Female , Middle Aged , COVID-19/epidemiology , Pandemics , Lupus Erythematosus, Systemic/epidemiology , Mass Media
7.
Lupus Sci Med ; 9(1)2022 05.
Article in English | MEDLINE | ID: mdl-35568437

ABSTRACT

OBJECTIVE: Previous research on coping strategies of patients with SLE showed that there are no absolute adaptive or maladaptive strategies and that the range of potential coping strategies is large and heterogeneous. In this paper, we aimed to identify, in a large sample of patients with SLE (N=3222), the most frequent words used by patients to describe their coping strategies, to group them into significant themes and to test their possible association with specific patient characteristics. METHODS: Our analyses were based on the data set of the European survey 'Living with Lupus in 2020' (N=3222). Through the T-LAB software, we analysed the answers that adult participants gave to an open-ended question about how they cope with the disease. We identified the most frequent words, and with hierarchical cluster analysis we grouped them into semantic clusters (ie, themes) that were characterised by specific patterns of words. Finally, we tested the possible association between clusters and illustrative variables (sociodemographics, disease characteristics, quality of life). RESULTS: Five coping strategies were identified, each of them constituting an important percentage of the total word occurrences: positive attitude (22.58%), social support (25.46%), medical treatments (10.77%), healthy habits (20.74%) and avoid stress (20.45%). Each strategy was statistically associated with specific patient characteristics, such as age and organ involvement. CONCLUSIONS: Learning to adapt to a lifetime of having SLE may require replacing old coping strategies with more effective ones. Investigating patients' coping strategies in relation to different patient characteristics represents a useful starting point for developing more targeted and efficacious interventions.


Subject(s)
Lupus Erythematosus, Systemic , Adaptation, Psychological , Adult , Humans , Lupus Erythematosus, Systemic/complications , Quality of Life , Surveys and Questionnaires
8.
Clin Exp Rheumatol ; 40 Suppl 134(5): 40-45, 2022 May.
Article in English | MEDLINE | ID: mdl-35349404

ABSTRACT

OBJECTIVES: To perform a systematic literature review (SLR) on the association of common variable immunodeficiency (CVID) and rare and complex connective tissue and musculoskeletal diseases, namely systemic lupus erythematosus (SLE), Sjögren's syndrome (SS), idiopathic inflammatory myopathies (IIM), systemic sclerosis (SSc), relapsing polychondritis, antiphospholipid syndrome, immunoglobulin (Ig) G4-related disease, as well as undifferentiated and mixed connective tissue disease. METHODS: An SLR on studies and cases about the association of CVID and rare and complex connective tissue and musculoskeletal diseases was performed. Animal studies were excluded. RESULTS: 170 publications fulfilled the inclusion criteria. Sjögren's syndrome was the most frequent connective tissue disease in CVID-patients. Most case reports exist on SLE and CVID with SLE mostly preceding the manifestation of CVID. Multiple cases were published reporting the concurrence of CVID and inclusion body myositis and single cases were found on CVID and antisynthetase syndrome, polymyositis, limited SSc and relapsing polychondritis, respectively. There are no cases of CVID and antiphospholipid syndrome, IgG4-related disease, as well as undifferentiated and mixed connective tissue disease. CONCLUSIONS: The concurrence of CVID and complex connective tissue and musculoskeletal diseases, especially SS, IIM, SSc and relapsing polychondritis is rare but relevant. The measurements of Ig-levels should be performed before the initiation of immunosuppressive therapy to allow for the differentiation of primary and secondary Ig-deficiency and substitute IG if necessary.


Subject(s)
Antiphospholipid Syndrome , Common Variable Immunodeficiency , Connective Tissue Diseases , Lupus Erythematosus, Systemic , Mixed Connective Tissue Disease , Musculoskeletal Diseases , Polychondritis, Relapsing , Scleroderma, Systemic , Sjogren's Syndrome , Antiphospholipid Syndrome/complications , Common Variable Immunodeficiency/complications , Connective Tissue , Connective Tissue Diseases/complications , Humans , Lupus Erythematosus, Systemic/complications , Mixed Connective Tissue Disease/complications , Musculoskeletal Diseases/etiology , Polychondritis, Relapsing/complications , Scleroderma, Systemic/complications , Sjogren's Syndrome/complications , Sjogren's Syndrome/diagnosis
9.
Clin Exp Rheumatol ; 40 Suppl 134(5): 3-11, 2022 May.
Article in English | MEDLINE | ID: mdl-35349419

ABSTRACT

In order to address the main challenges related to the rare diseases (RDs) the European Commission launched the European Reference Networks (ERNs), virtual networks involving healthcare providers (HCPs) across Europe. The mission of the ERNs is to tackle low prevalence and RDs that require highly specialised treatment and a concentration of knowledge and resources. In fact, ERNs offer the potential to give patients and healthcare professionals across the EU access to the best expertise and timely exchange of lifesaving knowledge, trying to make the knowledge travelling more than patients. For this reason, ERNs were established as concrete European infrastructures, and this is particularly crucial in the framework of rare and complex diseases in which no country alone has the whole knowledge and capacity to treat all types of patients.It has been five years since their kick-off launch in Vilnius in 2017. The 24 ERNs have been intensively working on different transversal areas, including patient management, education, clinical practice guidelines, patients' care pathways and many other fundamental topics. The present work is therefore aimed not only at reporting a summary of the main activities and milestones reached so far, but also at celebrating the first 5 years of the ERN on Rare and Complex Connective Tissue and Musculo-skeletal Diseases (ReCONNET), in which the members of the network built together one of the 24 infrastructures that are hopefully going to change the scenario of rare diseases across the EU.


Subject(s)
Musculoskeletal Diseases , Rare Diseases , Connective Tissue , Europe , Health Personnel , Humans , Musculoskeletal Diseases/diagnosis , Musculoskeletal Diseases/therapy , Rare Diseases/epidemiology , Rare Diseases/therapy
10.
Chronic Illn ; 18(2): 370-380, 2022 06.
Article in English | MEDLINE | ID: mdl-33092393

ABSTRACT

OBJECTIVE: The European Reference Network on Rare and Complex Connective Tissue and Musculoskeletal Diseases involves health care providers (HCPs) from 8 European countries and 7 patients' representatives of European Patient Advocacy Groups. The objective was to evaluate current practice and unmet needs for patient education (PE) in Europe. METHODS: A questionnaire was sent to HCP members asking about the PE practices and another, to enquire about their needs, was sent to patients' associations in the different countries. RESULTS: The questionnaire was completed by 33 HCPs. Half had no specific staff members dedicated to PE. For HCPs with dedicated staff, 83.3% (n = 11) considered that care providers were insufficient to meet patients' needs. Most of HCPs would like to see the practice of PE standardized. Sixty eight percent (n = 1093) of patients suffering from connective tissue diseases completed the questionnaire had never heard about PE. Most of them were interested in taking part in a PE program. DISCUSSION: Our survey revealed a strong interest in PE among patients and HCP and heterogeneity of practice. PE appeared important for both HCPs and patients. An online course for medical students in Europe will be developed in partnership with EULAR to respond to these unmet needs.


Subject(s)
Motivation , Musculoskeletal Diseases , Connective Tissue , Health Personnel , Humans , Musculoskeletal Diseases/therapy , Patient Education as Topic , Surveys and Questionnaires
11.
Lupus Sci Med ; 8(1)2021 05.
Article in English | MEDLINE | ID: mdl-34016719

ABSTRACT

Despite promising candidates for new therapeutic options in the treatment of systemic lupus erythematosus (SLE), many clinical trials have failed in the past few years. The disappointing results have been at least partly be attributed to trial designs. With the aim of stimulating new developments in SLE trial design, an international open space meeting was held on occasion of the European Lupus Meeting 2018 in Duesseldorf, Germany about 'What are the topics you care about for making trials in lupus more effective?'. The Open Space is a participant-driven technology, where the discussion topics and schedule are selected during the meeting by all participants and discussion rounds are led by the people attending encouraging active contributions. Eleven topics were selected for further discussion, of which 6 were voted to be more intensively discussed in two consecutive rounds. Major topics were the optimal handling of glucocorticoids in clinical trials, the improvement of outcome measures, reducing or controlling the placebo response and the identification of biomarkers and stratification parameters. Further, the importance of local and international networks was emphasised. By networking, collaborations are facilitated, patient recruitment is more efficient and treatment can be harmonised thus lead to more successful SLE trials. Further discussions are needed to substantiate the results and develop new trial designs.


Subject(s)
Lupus Erythematosus, Discoid , Lupus Erythematosus, Systemic , Germany , Glucocorticoids , Humans , Lupus Erythematosus, Systemic/therapy , Outcome Assessment, Health Care
12.
Lupus Sci Med ; 8(1)2021 03.
Article in English | MEDLINE | ID: mdl-33795484

ABSTRACT

BACKGROUND: Use of hydroxychloroquine (HCQ) is common in patients with lupus erythematosus. Long-term use (ie, ≥5 years) and high-dose HCQ (ie, >5 mg/kg/day) are both risk factors for developing HCQ retinopathy. Advances in our understanding of HCQ retinopathy have led to changes in the recommendations for HCQ dosing and retinopathy screening. The latest EULAR guidelines for the management of SLE recommend a maximum HCQ dose of 5 mg/kg/day and ophthalmological screening at baseline and annually after 5 years of HCQ treatment. OBJECTIVES: This study aimed to assess whether the EULAR guidelines are affecting HCQ prescription patterns and screening frequencies in Europe. Furthermore, we inventoried adherence to HCQ. RESULTS: The online questionnaire was completed by 2936 patients with systemic, cutaneous or juvenile lupus from 33 countries. The majority were female (86.5%) and diagnosed with SLE (81.2%). Among those taking HCQ, the median HCQ dose reported was 4.26 mg/kg/day. More than one-third of respondents (36.8%) exceeded the recommended maximal HCQ dose of 5 mg/kg/day. Baseline ophthalmological screening had been done in 857 out of 1017 respondents diagnosed in the past 10 years (84.3%). Of patients using HCQ ≥5 years, 69.2% reported yearly retinopathy screening. Lastly, 17.3% of patients reported that they skipped HCQ once a week or more often. CONCLUSION: The results of our study demonstrate that higher than recommended dosages of HCQ are prescribed to more than one-third of patients with lupus in Europe. Recent recommendations regarding screening for retinopathy are incompletely implemented.


Subject(s)
Hydroxychloroquine/adverse effects , Lupus Erythematosus, Systemic , Retinal Diseases , Adult , Antirheumatic Agents/therapeutic use , Europe , Female , Humans , Hydroxychloroquine/therapeutic use , Lupus Erythematosus, Systemic/drug therapy , Male , Middle Aged , Retinal Diseases/chemically induced
13.
Lupus Sci Med ; 8(1)2021 04.
Article in English | MEDLINE | ID: mdl-33849920

ABSTRACT

OBJECTIVE: The aim of this study was to analyse the 2020 burden of Systemic Lupus Erythematosus (SLE) in Europe, from the patients' perspective. METHODS: In May 2020, Lupus Europe, the European umbrella patient association for SLE, designed and disseminated a multilingual anonymous online survey to individuals with a self-reported physician's diagnosis of SLE living in Europe. RESULTS: Data from 4375 SLE survey respondents (95.9% women, median age: 45 (IQR: 36-54) years, 70.7% Caucasians) from 35 European countries were analysed. The median age at SLE diagnosis was 30 years (IQR: 22-40) and the median diagnosis delay was 2 years (IQR: 0-6). The most commonly affected organ-systems included the joints (81.8%) and skin (59.4%), with renal involvement in 30%. Another diagnosis was given before that of SLE in 45.0%, including psychological/mental disorders in 9.1% and fibromyalgia in 5.9%. The median number of symptoms reported was 9 (IQR: 6-11) out of 21, with fatigue most common (85.3%) and most bothersome. The median number of SLE-related medications was 5 (IQR: 3-7), including antimalarials (75%), oral glucocorticoids (52.4%), immunosuppressants (39.8%) and biologics (10.9%). Respondents reported significant impact over their studies, career and emotional/sexual life in 50.7%, 57.9% and 38.2%, respectively. Appropriate access to care was highly variable across countries and care component. CONCLUSION: This survey underlines the 2020 burden and strong heterogeneity in the care of SLE across Europe, from the patient's perspective. Altogether, these data may prove crucial to physicians, patients and policy-makers to improve the diagnosis and management of this rare and complex disease.


Subject(s)
Lupus Erythematosus, Systemic , Quality of Life , Adult , Child , Europe , Fatigue , Female , Humans , Male , Middle Aged , Surveys and Questionnaires
14.
Lupus Sci Med ; 8(1)2021 04.
Article in English | MEDLINE | ID: mdl-33875571

ABSTRACT

OBJECTIVE: To report the results of a survey exploring the experience of patients with SLE facing hydroxychloroquine (HCQ) shortage that occurred during the early phases of the COVID-19 pandemic. METHODS: A survey was designed by Lupus Europe's patient advisory network and distributed through its social media, newsflash and members' network. People with lupus were asked about their last HCQ purchases and their level of anxiety (on a 0-10 scale) with regard to not being able to have access to HCQ, once in April 2020 (first wave) and after 11 August (second wave). The results were compared. RESULTS: 2075 patients responded during the first wave; 1001 (48.2%) could get HCQ from the first place they asked, 230 (11.1%) could get the drug by going to more than one pharmacy, 498 (24.0%) obtained HCQ later from their usual pharmacy and 126 (6.1%) from other sources. 188 (9.1%) could not get any; 32 (1.5%) did not respond to this question. All countries showed significant improvement in HCQ availability during the second wave. 562 (27.4%) patients reported an extremely high level of anxiety in wave 1 and 162 (10.3%) patients in wave 2; 589 (28.7%) and 268 (17.1%) patients reported a high level of anxiety in wave 1 and wave 2, respectively. CONCLUSIONS: The HCQ shortage had a significant impact on patients with SLE and has been responsible for psychological consequences including anxiety. Indeed, despite an objective improvement in drug availability, the event is leaving significant traces in patients' mind and behaviours.


Subject(s)
Anxiety , COVID-19 Drug Treatment , COVID-19 , Community Pharmacy Services/statistics & numerical data , Health Services Accessibility , Hydroxychloroquine , Lupus Erythematosus, Systemic , Antirheumatic Agents/supply & distribution , Antirheumatic Agents/therapeutic use , Anxiety/diagnosis , Anxiety/etiology , COVID-19/epidemiology , Civil Defense/methods , Civil Defense/standards , Europe/epidemiology , Health Services Accessibility/standards , Health Services Accessibility/statistics & numerical data , Humans , Hydroxychloroquine/supply & distribution , Hydroxychloroquine/therapeutic use , Lupus Erythematosus, Systemic/drug therapy , Lupus Erythematosus, Systemic/epidemiology , Lupus Erythematosus, Systemic/psychology , Psychological Distress , SARS-CoV-2 , Self Report/statistics & numerical data , Surveys and Questionnaires
15.
Nat Rev Rheumatol ; 17(3): 177-184, 2021 03.
Article in English | MEDLINE | ID: mdl-33408338

ABSTRACT

During the COVID-19 pandemic, the need to provide high-level care for a large number of patients with COVID-19 has affected resourcing for, and limited the routine care of, all other conditions. The impact of this health emergency is particularly relevant in the rare connective tissue diseases (rCTDs) communities, as discussed in this Perspective article by the multi-stakeholder European Reference Network on Rare and Complex Connective Tissue and Musculoskeletal Diseases (ERN ReCONNET). The clinical, organizational and health economic challenges faced by health-care providers, institutions, patients and their families during the SARS-CoV-2 outbreak have demonstrated the importance of ensuring continuity of care in the management of rCTDs, including adequate diagnostics and monitoring protocols, and highlighted the need for a structured emergency strategy. The vulnerability of patients with rCTDs needs to be taken into account when planning future health policies, in preparation for not only the post-COVID era, but also any possible new health emergencies.


Subject(s)
COVID-19/epidemiology , Connective Tissue Diseases/epidemiology , Delivery of Health Care/organization & administration , Pandemics , SARS-CoV-2 , Comorbidity , Connective Tissue Diseases/therapy , Humans
16.
RMD Open ; 4(2): e000793, 2018.
Article in English | MEDLINE | ID: mdl-30564454

ABSTRACT

Systemic lupus erythematosus (SLE) is the paradigm of systemic autoimmune diseases characterised by a wide spectrum of clinical manifestations with an unpredictable relapsing-remitting course. The aim of the present work was to identify current available clinical practice guidelines (CPGs) for SLE, to provide their review and to identify physicians' and patients' unmet needs. Twenty-three original guidelines published between 2004 and 2017 were identified. Many aspects of disease management are covered, including global disease management, lupus nephritis and neuropsychiatric involvement, management of pregnancies, vaccinations and comorbidities monitoring. Unmet needs relate with disease management of some clinical manifestations and adherence to treatment. Many patient's unmet needs have been identified starting with faster diagnosis, need for more therapeutic options, guidelines on lifestyle issues, attention to quality of life and adequate education.

17.
Musculoskeletal Care ; 16(1): 67-73, 2018 03.
Article in English | MEDLINE | ID: mdl-28685926

ABSTRACT

Patient engagement is recognized as a crucial component of high-quality healthcare services. Among rheumatic diseases, systemic lupus erythematosus (SLE) appears particularly challenging for the engagement of patients in their own care. According to the patient health engagement (PHE) model, patient engagement is a dynamic phenomenon that proceeds through four experiential positions (blackout, arousal, adhesion and eudaimonic project). The aim of the present study was to describe the engagement process from the point of view and the experiences of SLE patients. Ten in-depth interviews and four focus groups were conducted with an international sample of SLE patients from different European countries. Transcripts were analysed through thematic content analysis. Findings showed that a fully engaged patient results from reframing emotional, cognitive and behavioural dimensions. The advances along the process depends on how the patient succeeds in each position. In conclusion, PHE represents an appropriate model by which to understand the engagement process of SLE patients. In order to meet patients' needs, healthcare providers and patient support groups should consider the specific position of SLE patients, providing adequate and tailored support.


Subject(s)
Lupus Erythematosus, Systemic/psychology , Patient Participation/psychology , Adult , Humans , Middle Aged , Young Adult
18.
Appl Opt ; 52(24): 5894-902, 2013 Aug 20.
Article in English | MEDLINE | ID: mdl-24084989

ABSTRACT

An electro-optic (EO) sensing system for measuring free-space electric fields in the microwave range has been developed. The system is based on a phase modulation heterodyning technique using a Mach-Zehnder interferometer. In one of the arms of the interferometer, an acousto-optic frequency shifter is used to downconvert the frequency of the detected signal in order to discriminate it from parasites emitted at the external electric field frequency. The sensing part is a LiTaO3 crystal placed in a Fabry-Perot cavity. The cavity aims at enhancing the sensitivity of the measurements. Cavity-based EO setups already used in the literature propose this sensitivity enhancement at the expense of the frequency bandwidth, whereas our setup allows this without a major impact on the frequency bandwidth. Electric fields are measured at both 15 kHz and 2.4 GHz with cavities of two different finesses; the best EO phase retardation gains obtained with the cavity are 34 and 60, respectively. The minimum detectable electric field is 0.003 V⋅m-1⋅Hz-1/2.

19.
Sensors (Basel) ; 12(4): 4074-90, 2012.
Article in English | MEDLINE | ID: mdl-22666019

ABSTRACT

Direct sunlight absorption by trace gases can be used to quantify them and investigate atmospheric chemistry. In such experiments, the main optical apparatus is often a grating or a Fourier transform spectrometer. A solar tracker based on motorized rotating mirrors is commonly used to direct the light along the spectrometer axis, correcting for the apparent rotation of the Sun. Calculating the Sun azimuth and altitude for a given time and location can be achieved with high accuracy but different sources of angular offsets appear in practice when positioning the mirrors. A feedback on the motors, using a light position sensor close to the spectrometer, is almost always needed. This paper aims to gather the main geometrical formulas necessary for the use of a widely used kind of solar tracker, based on two 45° mirrors in altazimuthal set-up with a light sensor on the spectrometer, and to illustrate them with a tracker developed by our group for atmospheric research.

20.
Opt Express ; 19(5): 4644-52, 2011 Feb 28.
Article in English | MEDLINE | ID: mdl-21369296

ABSTRACT

We report quantitative measurement of the relative proportion of δ- and ß-D-mannitol crystalline phases inserted into polyethylene powder pellets, obtained by time-domain terahertz spectroscopy. Nine absorption bands have been identified from 0.2 THz to 2.2 THz. The best quantification of the δ-phase proportion is made using the 1.01 THz absorption band. Coherent detection allows using the spectral phase shift of the transmitted THz waveform to improve the detection sensitivity of the relative δ-phase proportion. We argue that differential phase shift measurements are less sensitive to samples' defects. Using a linear phase shift compensation for pellets of slightly different thicknesses, we were able to distinguish a 0.5% variation in δ-phase proportion.


Subject(s)
Algorithms , Mannitol/analysis , Mannitol/chemistry , Terahertz Spectroscopy/methods , Crystallization , Phase Transition
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