To Bin or Not to Bin? A Comparison of Symptom Frequency Response Formats in The Assessment of Health-Related Quality of Life

Purpose The goal of this study is to compare three different types of retrospective frequency response formats on the Healthy Days Symptoms Module (HDSM). Responses are compared in terms of intra-individual consistency, psychometric value, and participant feedback about each type of response format. Methods Respondents each completed three versions of the HDSM, where items were framed to elicit an open-ended frequency, a fixed choice frequency, or a vague quantifier response. Traditional reliability statistics were used to evaluate intra-individual consistency. Differential item functioning (DIF) was used to test for response format effects, and item response theory (IRT) scale scores and standard errors were computed across the three forms to compare psychometric value. Linear mixed modeling was used to examine the associations of IRT scale scores across response formats with respondent characteristics. Results People are largely consistent in how they respond to items about their health, regardless of the response format, and no DIF was detected between response formats. The IRT scores computed from the “# of days” frequency response formats tend to have better measurement precision than those from vague quantifiers. Open-ended frequencies capture a greater span of individual differences for people reporting fewer symptoms; however, little measurement precision is lost in collapsing the frequencies into categories. Conclusions Both the open-ended and fixed choice frequency response formats offer more measurement precision than vague quantifiers. While the open-ended frequency response format may capture more individual differences, respondents tend to report more difficulty with exact frequency recall, and thus, prefer the fixed choice frequency format

A new multi-zone model for porosity distribution in Al–Si alloy castings

A new multi-zone model is proposed that explains how porosity forms in various regions of a casting under different conditions and leads to distinct zonal differences in pore shape, size and distribution. This model was developed by considering the effect of cooling rate on solidification and distribution of porosity in Al–Si alloys cast as plates in moulds made with silica, ilmenite or zirconia sand cores or steel chills facing the major plate faces. The alloys cast were Al–7 wt.% Si and Al–12.5 wt.% Si in unmodified and modified forms, the latter with either Na or Sr addition. It is found that, regardless of cooling condition, Si content and modification treatment, the microstructure can be divided into three zones of varying size (across the casting thickness) that are determined by the local cooling conditions and the nucleation and growth mode of the Al–Si eutectic. The zones are: (1) an outer shell-like zone where directional columnar dendritic grains and a fine-celled, coherent eutectic form a low-porosity shell at the casting surface; (2) a transitional zone where equiaxed, eutectic cells grow between columnar dendritic grains and irregular pores become trapped in the mush; and finally (3) a central zone where the thermal gradient is low and equiaxed dendritic grains and eutectic cells grow at the centre of the casting and larger, rounded pores tend to form. The paper discusses how Si content, modification type and cooling conditions influence the location and size (i.e. depth) of each of these zones and how the distribution of porosity is thus affected

Treating subclinical hypothyroidism in individuals with or without mental health problems - A Delphi based expert consensus study in two countries

Background: Subclinical hypothyroidism (SCH) is a common endocrine problem with prevalence estimates between 4% and 20%. Symptoms are often non-specific but can substantially affect well-being leading to repeated medical consultations. The effect of thyroid hormone replacement therapy (THRT) in patients with SCH remains uncertain. Current guidelines, limited by the lack of high-quality evidence, have been controversial with limited adherence in clinical practice. Methods: Three-round modified Delphi method to establish consensus regarding diagnosis and treatment of individuals with SCH with and without affective disorder or anxiety, conducted with clinicians from three specialties, general practice, endocrinology and psychiatry, and two countries, Sweden and the United Kingdom. Results: Sixty clinicians, 20 per specialty, were recruited. Fifty-three (88%) participants completed all three rounds. The participants reached consensus on five of the 26 practice statements that (a) repeated testing was required for the diagnosis of subclinical hypothyroidism, (b) antibody screening should usually occur, and (c and d) antibody screening would strengthen the indication for thyroid hormone replacement therapy in both individuals with or without affective disorder or anxiety. The participants disagreed with (e) a requirement of a TSH threshold ≥ 20 mIU/L for thyroid hormone replacement therapy start. Psychiatrists and GPs but not endocrinologists, agreed that there was a frequent discrepancy between laboratory results and clinical symptoms, and disagreed that testing for thyroid dysfunction was overused in patients presenting with depression or anxiety, or fatigue. Conclusions: In many aspects, attitudes toward diagnosing and treating SCH remain diverse. The inability of our Delphi panel to achieve consensus on most items and the disagreement with a TSH ≥ 20 mIU/L threshold for treatment suggest that the concept of SCH may need rethinking with a better understanding of the hypothalamic-pituitary-thyroid physiology. Given that the scientific evidence is currently not conclusive, guidelines in this area should not be taken as definitive.Originally included in thesis in manuscript form.</p

Hubschrauber Vibrationsreduktion unter Verwendung robuster Regelung

This dissertation presents a control law for helicopters to reduce vibration and to increase damping using individual blade control. H-infinity control synthesis is used to develop a robust controller usable in different operating conditions with different helicopter flight speeds. The control design is applied in simulation to the four-blade BO 105 helicopter rotor, which is equipped with an individual blade control system, where the pitch rod links are replaced by hydraulic actuators, allowing blade pitch control to be superimposed to the swashplate commands. Either oscillatory hub loads can be reduced or fuselage vibration can be targeted directly. As concerns hub loads, vibration can be cancelled (-99%) in three outputs simultaneously, e.g. in all three hub forces or in the vertical hub force and in the roll and pitch moments. A number of more than three outputs exceeds the number of three degrees of freedom available for vibration reduction of the four-blade rotor. Vibration can then only be reduced moderately, e.g. by -49%, for all three hub forces and for the two moments about the roll and pitch axis. Reducing hub vibration, however, does not necessarily lead to reduced vibration in the cabin. When individual blade control inputs, aimed at minimizing hub loads, are introduced, fuselage accelerations increase by a factor of up to three. Therefore, a finite-element model of the flexible fuselage is coupled with the aeromechanical rotor model. The resulting coupled rotor-fuselage model allows vibration to be calculated and controlled at locations in the cabin, such as at the pilot and copilot seats and in the load compartment. In simulation, a simultaneous vibration reduction of -89% is achieved at the pilot and copilot seats. The control law is developed with the constraint of no sensors and, consequently, no measurements in the rotating blades. However, to increase lag damping, the lag rates must be fed back. The use of a model-based control strategy enables lag damping to be enhanced from 0.5% to >3% critical damping by feeding back the observed lag rates, only requiring measurements of the hub loads. In order to consider the periodicity of the plant in the controller design, a time-periodic gain-scheduled controller is developed. The results of the simulation confirm the common viewpoint that incorporating more knowledge about the plant into the controller, instead of designing a more robust and thus conservative controller, improves performance or robustness against other influences.In dieser Dissertation wurde ein Regelgesetz zur Vibrationsreduktion und Schwenkdämpfungserhöhung für Hubschrauber mit Einzelblattsteuerung entwickelt. Das verwendete H-unendlich Reglerentwurfsverfahren erlaubte die Entwicklung eines robusten Reglers, welcher an Arbeitspunkten mit unterschiedlicher Fluggeschwindigkeit eingesetzt werden kann. Betrachtet wurde der Vier-Blatt-Rotor eines BO 105 Hubschraubers, dessen Rotoraktuatorik aus einer konventionellen Taumelscheibe und durch Hydraulikaktuatoren ersetzten umlaufenden Steuerstangen besteht. Die Vibrationsregelung nutzt die der Taumelscheibenansteuerung überlagerte Steuerung der Blattanstellwinkel durch die hydraulischen Aktuatoren im drehenden System. Als Zielgrößen für die Vibrationsreduktion können entweder oszillierende Rotornabenlasten oder direkt Vibrationen in der Zelle geregelt werden. Bei Rotornabenlasten als Zielgrößen ist eine Auslöschung (-99%) in drei Größen gleichzeitig möglich, z.B. in allen drei Rotornabenkräften oder der vertikalen Rotornabenkraft und den Rotornabenmomenten um die Roll- und Nickachse. Eine Auswahl von mehr als drei Zielgrößen zur Vibrationsreduktion übersteigt die Anzahl von drei vorhandenen Freiheitsgraden eines Vier-Blatt-Rotors und Vibrationen können nur noch teilweise reduziert werden, z.B. um -49% bei gleichzeitiger Regelung aller drei Nabenkräfte und der beiden Nabenmomente um die Roll- und Nickachse. Generell führt jedoch eine Reduktion der Vibrationen an der Rotornabe nicht zwangsläufig zu einem reduzierten Vibrationsniveau in der Hubschrauberzelle. Im Gegenteil, die Zellenvibrationen wurden durch eine Vibrationsreduktion an der Rotornabe um einen Faktor von bis zu drei erhöht. Daher wurde ein Finite-Elemente-Modell der flexiblen Hubschrauberzelle mit dem aerodynamischen Rotormodell gekoppelt. Das resultierende gekoppelte Rotor-Zellenmodell erlaubt die Berechnung und Regelung von Vibrationen an Positionen in der Hubschrauberzelle, wie die der Piloten- und Kopilotensitze und des Laderaums. Durch die direkte Regelung von Zellenvibrationen konnten die Vibrationen am Piloten- und Kopilotensitz in Simulationen um -89% reduziert werden. Das Regelgesetz wurde unter der Randbedingung entwickelt, dass keine Sensoren und folglich keine Messgrößen im rotierenden System zur Verfügung stehen. Die Zielsetzung der Schwenkdämpfungserhöhung erfordert jedoch die Rückführung der Schwenkraten der Rotorblätter. Die Verwendung einer modellbasierten Reglerstrategie erlaubte die Rückführung der beobachteten Schwenkraten und damit eine Erhöhung der Schwenkdämpfung von 0.5% auf bis zu >3% ohne Verwendung von Sensoren in den Rotorblättern. Um die Periodizität der Regelstrecke bereits im Reglerentwurf berücksichtigen zu können, wurde ein zeitperiodisch verstärkungsangepasster Regler entwickelt. Durch Simulationen konnte die Theorie bestätigt werden, dass die Verwendung von Informationen über die Regelstrecke, im Gegensatz zu der Entwicklung eines robusteren und damit konservativeren Reglers, zu einer verbesserten Leistungsfähigkeit oder zu einer erhöhten Robustheit gegenüber anderen Einflüssen führt

Rechnergestuetzte Verfahren zur Bildung von Ladeeinheiten

SIGLETIB Hannover: RN 7283(28) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Minutes of the Lone Star Chapter Sierra Club's Big Thicket Committee Meeting

Minutes for a meeting of the Sierra Club, Lone Star Chapte

Minutes of the Lone Star Chapter Sierra Club's Big Thicket Committee Meeting

Minutes for a meeting of the Sierra Club, Lone Star Chapte

Minutes of the Lone Star Chapter Sierra Club's Big Thicket Committee Meeting

Minutes for a meeting of the Sierra Club, Lone Star Chapte

Management of severe arterial hypertension associated with serotonin syndrome : a case report analysis based on systematic review techniques

Serotonin syndrome is thought to arise from serotonin excess. In many cases, symptoms are mild and self-limiting. But serotonin syndrome can become life threatening, when neuromuscular hyperexcitability spins out of control. Uncontainable neuromuscular hyperexcitability may lead to cardiovascular complications, linked to extreme changes in blood pressure. Currently, there is little guidance on how to control blood pressure in hyperserotonergic states. We report a case with treatment-resistant arterial hypertension, followed by a clinical review (using systematic review principles and techniques) of the available evidence from case reports published between 2004 and 2016 to identify measures to control arterial hypertension associated with serotonin syndrome. We conclude that classic antihypertensives may not be effective for the treatment of severe hypertension associated with serotonin syndrome. Benzodiazepines may lower blood pressure. Patients with severe hypertension not responding to benzodiazepines may benefit from cyproheptadine, propofol or both. In severe cases, higher cyproheptadine doses than currently recommended may be necessary