Decomposition of the mean absolute error (MAE) into systematic and unsystematic components.

When evaluating the performance of quantitative models, dimensioned errors often are characterized by sums-of-squares measures such as the mean squared error (MSE) or its square root, the root mean squared error (RMSE). In terms of quantifying average error, however, absolute-value-based measures such as the mean absolute error (MAE) are more interpretable than MSE or RMSE. Part of that historical preference for sums-of-squares measures is that they are mathematically amenable to decomposition and one can then form ratios, such as those based on separating MSE into its systematic and unsystematic components. Here, we develop and illustrate a decomposition of MAE into three useful submeasures: (1) bias error, (2) proportionality error, and (3) unsystematic error. This three-part decomposition of MAE is preferable to comparable decompositions of MSE because it provides more straightforward information on the nature of the model-error distribution. We illustrate the properties of our new three-part decomposition using a long-term reconstruction of streamflow for the Upper Colorado River.

A comparison of the physical demands associated with various right-angle direct-current power tools.

This work examined the physical demands associated with 4 commercially available direct current right-angle power tools along with their computer controlled fastening strategies. Physical demands were measured via an external instrumented handle that could also control the trigger of each tool. Data revealed that forces recorded by the external handle for each of the 4 tools differed. Independent of Joint-Hardness and Target Torque the Atlas Copco TurboTight® and Cleco Low Torque Reaction fastening strategies, both using a rapid spindle-head rotation strategy, produced the lowest peak and impulse force, respectfully, when compared to the 2 tools that were designed to fasten with a longer duration. This work has shown that short duration fastening strategies provide an ergonomics benefit to the users as it requires less force to operate, such force reduction in previous research has been linked to reduced handle displacement and lower muscle effort.

Physical demands associated with right-angle direct-current power-tools: An evaluation of current technology.

The purpose of this work was to evaluate the physical demands associated with three direct current powered right-angle power tool tightening strategies at various fastener-location-orientations, target torques and joint-hardness. Physical demands were measured using surface electromyography, handle force and upper body kinematics. Results identified TurboTight®, a rapid and short duration fastening strategy, to produce lower handle force impulse, less joint angle displacement, and lower EMG magnitudes when compared to the longer duration fastening strategies tested. The reduced magnitudes associated with TurboTight®, independent of fastener-location-orientations, target torques and joint-hardness, indicate a lower physical demand on power tool operators, providing a significant ergonomic benefit when compared to the slower fastening strategies.

Comparison of shoulder internal rotation passive range of motion in various positions in nonathletic persons and the establishment of normative values for the sidelying position.

BACKGROUND: Loss of shoulder internal rotation (IR) range of motion (ROM) is prevalent in overhead athletes, but it can also be seen in nonathletic persons. A paucity of normative data exists, however, for shoulder IR ROM in positions other than supine, especially in nonathletic persons. The aim of this study was to determine shoulder IR ROM differences between the sidelying, semi-sidelying, and supine positions as well as to establish initial normative values for IR ROM for the sidelying and semi-sidelying positions in nonathletic persons. METHODS: IR ROM was measured on 204 nonathletic persons using the sidelying, semi-sidelying, and supine positions. Mean values of IR ROM for each position were calculated. Differences in IR ROM across the 3 positions and side-to-side differences were examined, including the influence of sex and age on IR ROM. RESULTS: Intra-rater and inter-rater reliability for the sidelying position was excellent. The sidelying position had significantly less IR ROM compared with the other positions, and there was a significant side-to-side IR ROM difference, greatest for the sidelying position (6.8°). Women had significantly more IR ROM than men did, with sidelying normative values of 49° and 55° for female dominant and nondominant shoulders, respectively, and 42° and 51° for male dominant and nondominant shoulders, respectively. CONCLUSION: This investigation establishes initial normative IR ROM values for the sidelying position for both shoulders and sexes. Health care providers can begin to examine IR ROM deficits using these normative values for the sidelying position.

TOTAL ARC OF MOTION IN THE SIDELYING POSITION: EVIDENCE FOR A NEW METHOD TO ASSESS GLENOHUMERAL INTERNAL ROTATION DEFICIT IN OVERHEAD ATHLETES.

BACKGROUND: Total arc of motion (TA) measured in a supine position has been utilized as a method to detect the presence of glenohumeral internal rotation deficit (GIRD) in overhead athletes. A component of supine TA is supine internal rotation (IR) range of motion (ROM), which has many variables including the amount and location of manual stabilization. A sidelying position for gathering IR ROM has recently been proposed and, when combined with supine external rotation (ER) ROM, constitutes a new method of quantifying TA. This new sidelying TA method, however, has no normative values for overhead athletes. PURPOSE: The purposes of this study were to develop normative values for sidelying TA in overhead athletes, determine any ROM difference between supine and sidelying TA, and examine side-to-side differences within the two TA methods. A secondary purpose of the study was to examine for any effect of gender or level of competition on the two TA methods. STUDY DESIGN: Cross-sectional study. METHODS: Passive supine IR ROM, supine ER ROM, and sidelying IR ROM were gathered on bilateral shoulders of 176 collegiate and recreational overhead athletes (122 male [21.4 ± 4.7 years, 71.7 ± 2.7 inches, 25.3 ± 2.7 BMI] and 54 female [21.4 ± 5.4 years, 67.6 ± 3.0 inches, 22.5 ± 2.37 BMI]). RESULTS: Sidelying TA mean for the dominant shoulder was 159.6 °±15.0 °; the non-dominant shoulder was 163.3 °±15.3 °. Sidelying TA for both shoulders (p < 0.0001) was 14 ° less than supine TA. Both TA methods exhibited a 4 ° dominant-shoulder deficit (p < 0.0001). For the dominant and non-dominant shoulder, respectively, there was no gender (p = 0.38, 0.54) or level of competition (p = 0.23, 0.39) effect on sidelying TA. CONCLUSION: In overhead athletes, sidelying TA is a viable alternative to supine TA when examining for the presence of GIRD. Gender and level of competition does not significantly affect sidelying TA, so the mean of 160 ° on the dominant shoulder and 163 ° on the non-dominant shoulder can be used by clinicians. LEVEL OF EVIDENCE: Level 3.

Reliability of shoulder internal rotation passive range of motion measurements in the supine versus sidelying position.

STUDY DESIGN: Clinical measurement, reliability. OBJECTIVE: To compare intrarater and interrater reliability of shoulder internal rotation (IR) passive range of motion measurements utilizing a standard supine position and a sidelying position. BACKGROUND: Glenohumeral IR range of motion deficits are often noted in patients with shoulder pathology. Excellent intrarater reliability has been found when measuring this motion. However, interrater reliability has been reported as poor to fair. Some clinicians currently use a sidelying position for IR stretching with patients who have shoulder pathology. However, no objective data exist for IR passive range of motion measured in this sidelying position, either in terms of reliability or normative values. METHODS: Seventy subjects (mean age, 36.8 years), with (n = 19) and without (n = 51) shoulder pathology, were included in this study. Shoulder IR passive range of motion of the dominant shoulder or involved shoulder was measured by 2 investigators in 2 positions: (1) a standard supine position, with the shoulder at 90 degrees of abduction, and (2) in sidelying on the tested side, with the shoulder flexed to 90 degrees . RESULTS: Intrarater reliability for supine measurements was good to excellent (ICC3,1 = 0.70-0.93) and for sidelying measurements was excellent (ICC3,1 = 0.94-0.98). Interrater reliability was fair to good for the supine measurement (ICC2,2 = 0.74-0.81) and good to excellent for the sidelying measurement (ICC2,2 = 0.88-0.96). The mean (range) value of the dominant shoulder sidelying IR passive range of motion was 40 degrees (11 degrees to 69 degrees ) for healthy subjects and 25 degrees (-16 degrees to 49 degrees) for subjects with shoulder pathology. CONCLUSIONS: For subjects with shoulder pathology, measurements of shoulder IR made in the sidelying position had superior intrarater and interrater reliability compared to those in the standard supine position.

A longitudinal analysis of the effects of a preventive exercise programme on the factors that predict shoulder pain in construction apprentices.

Construction apprentices are at risk for developing shoulder pain with increasing exposure to repetitive overhead work. Risk may decrease if shoulder biomechanics are optimised and if risk factors that contribute to shoulder pain onset are identified. This prospective cohort study examined demographic and work-related factors and shoulder pain onset over 2 years in a cohort of 240 construction apprentices. Approximately 50% of the sample (n=117) performed a home exercise programme intended to have a protective effect, while the other 50% served as controls. The proportion of new-onset shoulder pain in the control group was higher than in the exercise group. Regression analysis identified four factors related to new-onset shoulder pain: previous neck pain; working in hot, cold or humid conditions; subject height; and bending and twisting the back. This information may assist employers and workers in preventing shoulder pain. By knowing factors predictive of shoulder pain development in construction workers, employers can take measures to protect workers and may secondarily decrease medical expenses and maintain productivity. Previous neck pain, working in extreme environmental conditions and being shorter all increased a worker's risk of developing shoulder pain. Exercises to optimise shoulder biomechanics have a small effect on preventing shoulder pain development.

Motion of the shoulder complex during multiplanar humeral elevation.

BACKGROUND: Many prior studies have evaluated shoulder motion, yet no three-dimensional analysis comparing the combined clavicular, scapular, and humeral motion during arm elevation has been done. We aimed to describe and compare dynamic three-dimensional motion of the shoulder complex during raising and lowering the arm across three distinct elevation planes (flexion, scapular plane abduction, and coronal plane abduction). METHODS: Twelve subjects without a shoulder abnormality were enrolled. Transcortical pin placement into the clavicle, scapula, and humerus allowed electromagnetic motion sensors to be rigidly fixed. The subjects completed two repetitions of raising and lowering the arm in flexion, scapular, and abduction planes. Three-dimensional angles were calculated for sternoclavicular, acromioclavicular, scapulothoracic, and glenohumeral joint motions. Joint angles between humeral elevation planes and between raising and lowering of the arm were compared. RESULTS: General patterns of shoulder motion observed during humeral elevation were clavicular elevation, retraction, and posterior axial rotation; scapular internal rotation, upward rotation, and posterior tilting relative to the clavicle; and glenohumeral elevation and external rotation. Clavicular posterior rotation predominated at the sternoclavicular joint (average, 31 degrees). Scapular posterior tilting predominated at the acromioclavicular joint (average, 19 degrees). Differences between flexion and abduction planes of humerothoracic elevation were largest for the glenohumeral joint plane of elevation (average, 46 degrees). CONCLUSIONS: Overall shoulder motion consists of substantial angular rotations at each of the four shoulder joints, enabling the multiple-joint interaction required to elevate the arm overhead.

Three-dimensional acromioclavicular joint motions during elevation of the arm.

STUDY DESIGN: Descriptive laboratory study. OBJECTIVES: To determine the 3-dimensional motions occurring between the scapula relative to the clavicle at the acromioclavicular joint during humeral elevation in the scapular plane. BACKGROUND: Shoulder pathology is commonly treated through exercise programs aimed at correcting scapular motion abnormalities. However, little is known regarding how acromioclavicular joint motions contribute to normal and abnormal scapulothoracic motion. METHODS AND MEASURES: Thirty subjects (16 males, 14 females) participated. Subjects with positive symptoms on clinical exam or past history of shoulder pathology, trauma, or surgery were excluded. Electromagnetic surface motion analysis was performed tracking the thorax, clavicle, scapula, and humerus. Subjects performed 3 repetitions of scapular plane abduction. Passive motion data were also collected for scapular plane abduction from cadaver specimens. Data were analyzed using within-session reliability and descriptive statistics as well as repeated measures analyses of variance (ANOVAs) to determine the effect of elevation angle from rest to 90 masculine humeral elevation. Reliability was determined from repeated trials in the same session without removing sensors or redigitizing landmarks. RESULTS: Angular values were highly repeatable within session (ICC>0.94; SEM, < 2.3 degrees ). During active scapular plane abduction from rest to 90 degrees , average acromioclavicular joint angular values demonstrated increased internal rotation (approximately 4.3 degrees ), increased upward rotation (approximately 14.6 degrees ), and increased posterior tilting (approximately 6.7 degrees ) (P<.05). Passive motions on cadavers demonstrated similar kinematic patterns. CONCLUSIONS: Significant motion occurs at the acromioclavicular joint during active humeral elevation, contributing to scapular motion on the thorax. This information provides a foundation for understanding normal acromioclavicular joint motion as a basis for further investigation of pathology and rehabilitation approaches.

Scapular angular positioning at end range internal rotation in cases of glenohumeral internal rotation deficit.

STUDY DESIGN: Controlled laboratory study. OBJECTIVES: Investigate the relationship between glenohumeral internal rotation range-of-motion deficit and 3-dimensional scapular angular positioning during active arm movements in participants with recent participation in overhead sports activity. BACKGROUND: Subacromial impingement is one of the most common shoulder pathologies and is multifactorial in etiology. Posterior glenohumeral joint capsule tightness has been theorized to contribute to one potential causal factor: abnormal scapular positioning. METHODS AND MEASURES: Twenty-three subjects, who had participated in competitive sports involving overhead activity within the last 5 years, were categorized into 2 groups based on the degree of glenohumeral internal rotation deficit (20% deficit threshold). Scapular angular positioning of subjects performing shoulder internal rotation from 90 degrees flexion and abduction shoulder positions was evaluated using 3-dimensional electromagnetic surface tracking. Additional sensors monitored trunk and humeral motion. Scapular position data at end range glenohumeral internal rotation, along with glenohumeral internal rotation range of motion measurements, were used to analyze the relationship between glenohumeral internal rotation deficit and scapular position using 2-way ANOVA and regression analyses. RESULTS: The internal rotation deficit group had significantly greater scapular anterior tilt (9.2 degrees difference, P = .04) across positions, as compared to the control group. Regression analysis demonstrated a significant association between glenohumeral internal rotation deficit and scapular position (tilting) during flexed internal rotation (r(2) = 0.37, P = .03) and for scapular position (anterior tilting and upward rotation) during abducted internal rotation (r = 0.35, P = .036). CONCLUSIONS: These findings demonstrate a significant relationship between glenohumeral internal rotation deficit and abnormal scapular positioning, particularly increased anterior tilt. This relationship identifies a possible mechanism for development of excessive scapular anterior tilt.

Anaesthesia for cardioversion: a comparison of sevoflurane and propofol.

This study compared the induction time, haemodynamic changes, recovery characteristics and patient satisfaction for sevoflurane and propofol when used as the main anaesthetic agents for cardioversion. Sixty-one unpremedicated patients scheduled for elective cardioversion were anaesthetised with either inhaled sevoflurane 8% or an intravenous propofol target-controlled infusion set at 6 microg.ml(-1). There was no significant difference in induction time between the two groups: mean (SD) = 90.1(40) s in the sevoflurane group vs. 83.7(35) s in the propofol group. Mean (SD) time to recovery was significantly shorter in the sevoflurane group than in the propofol group: 318 (127) s vs.738 (355) s, respectively, p < 0.001. At recovery, the patients in the propofol group had significantly lower systolic and diastolic blood pressures than those in the sevoflurane group, p < 0.001. The incidence of complications was low in both groups, with similar patient satisfaction expressed after the procedure. We conclude that sevoflurane is a suitable choice for anaesthesia for cardioversion and may provide greater haemodynamic stability than a target-controlled infusion of propofol.

Solution structure of Pyrobaculum aerophilum DsrC, an archaeal homologue of the gamma subunit of dissimilatory sulfite reductase.

The solution structure of DsrC, an archaeal homologue of the gamma subunit of dissimilatory sulfite reductase, has been determined by NMR spectroscopy. This 12.7-kDa protein from the hyperthermophilic archaeon Pyrobaculum aerophilum adopts a novel fold consisting of an orthogonal helical bundle with a beta hairpin along one side. A portion of the structure resembles the helix-turn-helix DNA-binding motif common in transcriptional regulator proteins. The protein contains two disulfide bonds but remains folded following reduction of the disulfides. DsrC proteins from organisms other than Pyrobaculum species do not contain these disulfide bonds. A conserved cysteine next to the C-terminus, which is not involved in the disulfide bonds, is located on a seven-residue C-terminal arm that is not part of the globular protein and is likely to dynamically sample more than one conformation.

Structural proteomics of an archaeon.

A set of 424 nonmembrane proteins from Methanobacterium thermoautotrophicum were cloned, expressed and purified for structural studies. Of these, approximately 20% were found to be suitable candidates for X-ray crystallographic or NMR spectroscopic analysis without further optimization of conditions, providing an estimate of the number of the most accessible structural targets in the proteome. A retrospective analysis of the experimental behavior of these proteins suggested some simple relations between sequence and solubility, implying that data bases of protein properties will be useful in optimizing high throughput strategies. Of the first 10 structures determined, several provided clues to biochemical functions that were not detectable from sequence analysis, and in many cases these putative functions could be readily confirmed by biochemical methods. This demonstrates that structural proteomics is feasible and can play a central role in functional genomics.

Structure-based functional classification of hypothetical protein MTH538 from Methanobacterium thermoautotrophicum.

The structure of MTH538, a previously uncharacterized hypothetical protein from Methanobacterium thermoautotrophicum, has been determined by NMR spectroscopy. MTH538 is one of numerous structural genomics targets selected in a genome-wide survey of uncharacterized sequences from this organism. MTH538 is a so-called singleton, a sequence not closely related to any other (known) sequences. The structure of MTH538 closely resembles the known structures of receiver domains from two component response regulator systems, such as CheY, and is similar to the structures of flavodoxins and GTP-binding proteins. Tests on MTH538 for characteristic activities of CheY and flavodoxin were negative. MTH538 did not become phosphorylated in the presence of acetyl phosphate and Mg(2+), although it appeared to bind Mg(2+). MTH538 also did not bind flavin mononucleotide (FMN) or coenzyme F(420). Nevertheless, sequence and structure parallels between MTH538/CheY and two families of ATPase/phosphatase proteins suggest that MTH538 may have a role in a phosphorylation-independent two-component response regulator system.

NMR structure determination and structure-based functional characterization of conserved hypothetical protein MTH1175 from Methanobacterium thermoautotrophicum.

The solution structure of MTH1175, a 124-residue protein from the archaeon Methanobacterium thermoautotrophicum has been determined by NMR spectroscopy. MTH1175 is part of a family of conserved hypothetical proteins (COG1433) with unknown functions which contains multiple paralogs from all complete archaeal genomes and the archaeal gene-rich bacterium Thermotoga maritima. Sequence similarity indicates this protein family may be related to the nitrogen fixation proteins NifB and NifX. MTH1175 adopts an alpha/beta topology with a single mixed beta-sheet, and contains two flexible loops and an unstructured C-terminal tail. The fold resembles that of Ribonuclease H and similar proteins, but differs from these in several respects, and is not likely to have a nuclease activity.

A phylogenetic approach to target selection for structural genomics: solution structure of YciH.

Structural genomics presents an enormous challenge with up to 100 000 protein targets in the human genome alone. At current rates of structure deter-mination, judicious selection of targets is necessary. Here, a phylogenetic approach to target selection is described which makes use of the National Center for Biotechnology Information database of Clusters of Orthologous Groups (COGS). The strategy is designed so that each new protein structure is likely to provide novel sequence-fold information. To demonstrate this approach, the NMR solution structure of YciH (COG0023), a putative translation initiation factor from Escherichia coli, has been determined and its fold classified. YciH is an ortholog of eIF-1/SUI1, an integral component of the translation initiation complex in eukaryotes. The structure consists of two antiparallel alpha-helices packed against the same side of a five-stranded beta-sheet. The first 31 residues of the 11.5 kDa protein are unstructured in solution. Comparative analysis indicates that the folded portion of YciH resembles a number of structures with the alpha-beta plait topology, though its sequence is not homologous to any of them. Thus, the phylogenetic approach to target selection described here was used successfully to identify a new homologous superfamily within this topology.

Formation of a molten-globule-like state of myoglobin in aqueous hexafluoroisopropanol.

The effects of aqueous hexafluoroisopropanol (HFIP) media on the structure of myoglobin are reported. Circular dichroism (CD) spectra of this alpha-helical protein in as little as 4% (v/v) HFIP indicate that native-like amounts of secondary structure remain while rigid tertiary structure is lost. However, thermal studies suggest some residual cooperativity of unfolding in this state. At much higher HFIP concentrations, the helicity exceeds the native value and the protein behaves as a series of independent helices which do not interact with each other. We did not observe cold denaturation of myoglobin, even though this phenomenon has been observed for molten globule states of myoglobin, as well as for monomeric amphipathic alpha-helices when moderate quantities of HFIP are present. The pH dependence of trifluoroethanol-induced disruption of tertiary structure revealed that the degree of disruption increases as the enthalpic advantage of the folded state is diminished at low pH.

Beta-structure in human amylin and two designer beta-peptides: CD and NMR spectroscopic comparisons suggest soluble beta-oligomers and the absence of significant populations of beta-strand dimers.

Intensity variation for the positive far UV CD band was observed for three 'beta-sheet' peptides. In 6% HFIP, an amyloidogenic species (human pancreatic amylin) displays, on standing, an extremely intense 192-nm band which diminishes upon physical agitation. A concurrently formed Tyr sidechain band at 274 nm disappears completely with agitation, linking the enhancement of the 192-nm band to the highly ordered stacking of beta-sheets. NMR studies indicate that the beta-states of the three peptides are oligomeric, not beta dimers. A membrane-forming EAK peptide displays NMR peaks due to the low concentration of 'random coil' monomers present in slow equilibrium with beta-oligomers; solutions of a more hydrophobic ELKA peptide, which displays an intense 195-nm band, contain only oligomeric species. NMR studies at 25% HFIP revealed the structural requirements for inhibition of beta-oligomer formation.

[Leiomyoma and leiomyosarcoma of the gastrointestinal system: experience with 5 patients and literature review]. / Leiomyomen en leiomyosarcomen van het gastro-intestinaal stelsel: ervaring met 5 patiënten en literatuuroverzicht.

Leiomyomas and leiomyosarcomas of the gastro-intestinal tract are quite uncommon tumours. Clinical findings are aspecific: abdominal pain and gastrointestinal bleeding. Diagnosis is made by X-ray with contrast, endoscopy and CT-scan. Although biopsies taken during endoscopy are considered to be useless, our experiences showed an accurate diagnosis with biopsies. Surgery is the only treatment. The aim is to reduce the mass of tumour as much as possible; second look operations with careful debulking enhances the survival in case of recidive. Resection of lymph-nodes is useless. Radiotherapy nor chemotherapy are proven to be useful. The grade of malignity determines the prognosis. The liver and the abdominal cavity are the predilected localisation for metastasis. Metastasis in lymph-nodes is uncommon. Five year survival is about 50%.