Study protocol: Transition from localized low back pain to chronic widespread pain in general practice: identification of risk factors, preventive factors and key elements for treatment--a cohort study

Background Chronic localized pain syndromes, especially chronic low back pain (CLBP), are common reasons for consultation in general practice. In some cases chronic localized pain syndromes can appear in combination with chronic widespread pain (CWP). Numerous studies have shown a strong association between CWP and several physical and psychological factors. These studies are population-based cross-sectional and do not allow for assessing chronology. There are very few prospective studies that explore the predictors for the onset of CWP, where the main focus is identifying risk factors for the CWP incidence. Until now there have been no studies focusing on preventive factors keeping patients from developing CWP. Our aim is to perform a cross sectional study on the epidemiology of CLBP and CWP in general practice and to look for distinctive features regarding resources like resilience, self-efficacy and coping strategies. A subsequent cohort study is designed to identify the risk and protective factors of pain generalization (development of CWP) in primary care for CLBP patients. Methods/Design Fifty-nine general practitioners recruit consecutively, during a 5 month period, all patients who are consulting their family doctor because of chronic low back pain (where the pain is lasted for 3 months). Patients are asked to fill out a questionnaire on pain anamnesis, pain-perception, co-morbidities, therapy course, medication, socio demographic data and psychosomatic symptoms. We assess resilience, coping resources, stress management and self-efficacy as potential protective factors for pain generalization. Furthermore, we raise risk factors for pain generalization like anxiety, depression, trauma and critical life events. During a twelve months follow up period a cohort of CLBP patients without CWP will be screened on a regular basis (3 monthly) for pain generalization (outcome: incident CWP). Discussion This cohort study will be the largest study which prospectively analyzes predictors for transition from CLBP to CWP in primary care setting. In contrast to the typically researched risk factors, which increase the probability of pain generalization, this study also focus intensively on protective factors, which decrease the probability of pain generalization.

Macro Monte Carlo for dose calculation of proton beams

Although the Monte Carlo (MC) method allows accurate dose calculation for proton radiotherapy, its usage is limited due to long computing time. In order to gain efficiency, a new macro MC (MMC) technique for proton dose calculations has been developed. The basic principle of the MMC transport is a local to global MC approach. The local simulations using GEANT4 consist of mono-energetic proton pencil beams impinging perpendicularly on slabs of different thicknesses and different materials (water, air, lung, adipose, muscle, spongiosa, cortical bone). During the local simulation multiple scattering, ionization as well as elastic and inelastic interactions have been taken into account and the physical characteristics such as lateral displacement, direction distributions and energy loss have been scored for primary and secondary particles. The scored data from appropriate slabs is then used for the stepwise transport of the protons in the MMC simulation while calculating the energy loss along the path between entrance and exit position. Additionally, based on local simulations the radiation transport of neutrons and the generated ions are included into the MMC simulations for the dose calculations. In order to validate the MMC transport, calculated dose distributions using the MMC transport and GEANT4 have been compared for different mono-energetic proton pencil beams impinging on different phantoms including homogeneous and inhomogeneous situations as well as on a patient CT scan. The agreement of calculated integral depth dose curves is better than 1% or 1 mm for all pencil beams and phantoms considered. For the dose profiles the agreement is within 1% or 1 mm in all phantoms for all energies and depths. The comparison of the dose distribution calculated using either GEANT4 or MMC in the patient also shows an agreement of within 1% or 1 mm. The efficiency of MMC is up to 200 times higher than for GEANT4. The very good level of agreement in the dose comparisons demonstrate that the newly developed MMC transport results in very accurate and efficient dose calculations for proton beams.

Study of the Compressive Strength of Aluminum Curved Elements

Currently, the Specification for Aluminum Structures (Aluminum Association, 2010) shows thin-walled aluminum plate sections with radii greater than eight inches have a lower compressive strength capacity than a flat plate with the same width and thickness. This inconsistency with intuition, which suggests any degree of folding a plate should increase its elastic buckling strength, inspired this study. A wide range of curvatures are studied—from a nearly flat plate to semi-circular. To quantify the curvature, a single non-dimensional parameter is used to represent all combinations of width, thickness and radius. Using the finite strip method (CU-FSM), elastic local buckling stresses are investigated. Using the ratio of stress values of curved plates compared to flat plates of the same size, equivalent plate-buckling coefficients are calculated. Using this data, nonlinear regression analyses are performed to develop closed form equations for five different edge support conditions. These equations can be used to calculate the elastic critical buckling stress for any curved aluminum section when the geometric properties (width, thickness, and radius) and the material properties (elastic modulus and Poisson’s ratio) are known. This procedure is illustrated in examples, each showing the applicability of the derived equations to geometries other than those investigated in this study and also providing comparisons with theoretically exact numerical analysis results.

3CAM - A NOVEL TERNARY CONTENT ADDRESSABLE MEMORY USING THREE-VALUED LOGIC

Content Addressable Memory (CAM) is a special type of Complementary Metal-Oxide-Semiconductor (CMOS) storage element that allows for a parallel search operation on a memory stack in addition to the read and write operations yielded by a conventional SRAM storage array. In practice, it is often desirable to be able to store a “don’t care” state for faster searching operation. However, commercially available CAM chips are forced to accomplish this functionality by having to include two binary memory storage elements per CAM cell,which is a waste of precious area and power resources. This research presents a novel CAM circuit that achieves the “don’t care” functionality with a single ternary memory storage element. Using the recent development of multiple-voltage-threshold (MVT) CMOS transistors, the functionality of the proposed circuit is validated and characteristics for performance, power consumption, noise immunity, and silicon area are presented. This workpresents the following contributions to the field of CAM and ternary-valued logic:• We present a novel Simple Ternary Inverter (STI) transistor geometry scheme for achieving ternary-valued functionality in existing SOI-CMOS 0.18µm processes.• We present a novel Ternary Content Addressable Memory based on Three-Valued Logic (3CAM) as a single-storage-element CAM cell with “don’t care” functionality.• We explore the application of macro partitioning schemes to our proposed 3CAM array to observe the benefits and tradeoffs of architecture design in the context of power, delay, and area.

The Experience of Micro and Macro Events: A Life-Span Analysis

This study investigated how individuals retrospectively construe their lives in terms of major life events. Ninety-nine participants sorted a set of personal and historical events in terms of perceived importance for their lives. Analyses of variance with repeated measures and rank comparisons were computed. Overall findings revealed no cohort differences with regard to the perception of life events. However, within-cohort differences were found, indicating that more life events were recalled from the young adult years. Those experiences were also perceived as having been more important in the participants' lives than events from other age segments. With regard to historical events, war-related experiences were among the highest ranked. Analyses of variance revealed intracohort differences but not intercohort differences, indicating higher scores for the time between 1930 and 1948 relative to other historical periods.