Suitability of different machine learning algorithms for the classification of the proportion of grassland-based forages at herd-level using mid-infrared spectral information from routine milk control.

As the call for an international standard for milk from grassland-based production systems continues to grow, so too do the monitoring and evaluation policies surrounding this topic. Individual stipulations by countries and milk producers to market their milk under their own grass-fed labels include a compulsory number of grazing days per year, ranging from 120 d for certain labels to 180 d for others, a specified amount of herbage in the diet or a prescribed dietary proportion of grassland-based forages (GBF) fed and produced on farm. As these multifarious policy and label requirements are laborious and costly to monitor on farm, fast economical proxies would be advantageous to verify the proportion of GBF consumed by the cows in the final product. With this in mind, we employed readily available mid-infrared spectral data (n = 1132 spectra) from routine milk controls to develop binary classification models for 4 main feed groups from a primarily forage-based diet: Total GBF (≥50% n = 955, ≥ 75% n = 599, ≥ 85% n = 356), pasture (≥20% n = 451, ≥ 50% n = 284, ≥ 70% n = 152), fresh herbage (pasture + fresh herbage indoor feeding, ≥ 20% n = 517, ≥ 50% n = 325, ≥ 70% n = 182) and whole plant corn (fresh + conserved) (≥10% n = 646, ≥ 30% n = 187), the latter as a negative control. We compared 4 machine learning methods to assess which statistical model performs best at discriminating these classes. Three of these models have not yet been tested for herd-level dietary proportion classification and all 4 follow completely different approaches: least absolute shrinkage and selection operator (LASSO), partial least squares discriminant analysis (PLS-DA), random forest (RF) and support vector machines (SVM). Seasonality has been a missing element from previous dietary herbage proportion classification models. As grazing and fresh herbage indoor feeding are highly dependent on the season, we developed an indicator to incorporate seasonality in a consistent, unbiased manner into our models. We also tested 3 sets of covariates. The first set included only mid-infrared spectra derived data, the second included mid-infrared spectra derived data plus seasonality indices and the third included mid-infrared spectra derived data, seasonality indices and additional herd specific information (DIM, breed and parity). Of the 4 machine learning algorithms tested for the binary classification of GBF proportion at herd level, LASSO and PLS-DA performed best according to evaluation metrics; however, the RF and SVM models were not far behind the best performing model evaluation metrics in each feed category. Our best performing model, the LASSO model containing seasonality indices and herd specific information, classified total GBF ≥50% with an accuracy of 78.6%, precision of 85.1%, sensitivity of 90.6%, specificity 14.1% and F1 score (harmonic mean of precision and sensitivity) of 87.7%, this was very similar to the PLS-DA model. Our results suggest that in general LASSO and PLS-DA machine learning algorithms perform better for dietary GBF classification than RF or SVM algorithms.

Patients' satisfaction after a comprehensive assessment for complex chronic facial pain at a specialised unit: results from a prospective audit.

OBJECTIVE: The aim of this audit was to investigate complex chronic facial pain patients' satisfaction after an initial, comprehensive, 45-60 minute consultation visit. DESIGN: Prospective audit using a post-visit satisfaction survey. SETTING: Specialised outpatient facial pain unit. METHODS: A convenience sample of 50 consecutive new patients were recruited. History, pain and psychosocial functioning were assessed through standard, validated pre-visit questionnaires. A post-visit satisfaction questionnaire was sent (twice if necessary) to patients by mail, and non-responders were contacted by telephone. MAIN OUTCOME MEASURES: Patients' satisfaction scores on pain management processes were evaluated. RESULTS: Response rate for the questionnaire was 63% (32/50) and 12 additional patients who did not respond to the questionnaire replied by telephone. Among questionnaire respondents, mean overall patient satisfaction was 8.1 ± 2.2 on an 11-point scale (best score 10), with no differences based on age, gender, diagnosis, length of symptoms and treatment. There was a trend of higher overall satisfaction among patients referred by dentists and specialists. Patients who had seen at least one specialist before their visit reported higher scores in understanding the reasons for their condition and what to do to treat their condition. CONCLUSIONS: A consultation with adequate time for history taking, addressing patients' goals and thorough explanation accompanied by written information, results in high satisfaction among patients with chronic facial pain.

Soft tissue wobbling affects trunk dynamic response in sudden perturbations.

Soft tissue wobbling reduces the transferred impact of external loads on lower limb joints. The present study investigated whether soft tissue wobbling has similar effects on trunk dynamic response to sudden perturbations. Three healthy males were subjected to a series of anteriorly directed trunk position perturbations at three different velocities while trunk kinematics and kinetics were measured. A nonlinear active-passive finite element model of the human trunk was then used to study the effects of soft tissue wobbling on trunk response. Also investigated were the effects on model predictions of including elements simulating the apparatus (rod-harness assembly) transferring motor-generated perturbations to the trunk. Predicted and measured trunk kinematics and kinetics, when accounting for the dynamic effects of both wobbling mass and rod-harness assembly, were in good agreement for all velocities especially early (<120 ms) after the perturbations (ρ>0.97). Root mean square errors in model predictions increased considerably when neglecting the aforementioned modeling considerations. The trunk wobbling mass and connecting elements between the trunk and the perturbing device, particularly during faster perturbations, substantially attenuated the transferred impact of external loads on the spine (by 33-90 N across perturbation velocities). Such reductions in the impacts transferred, in turn, reduced the predicted demands on the neuromuscular system for control and maintenance of spinal loads and stability. As such, these features should be considered in future biodynamic models of the human trunk aimed at estimating trunk neuromuscular behaviors during sudden perturbations.

Can timing of tracheal extubation predict improved outcomes after cardiac surgery?

INTRODUCTION: Early tracheal extubation is a common goal after cardiac surgery. Our study aims to examine whether timing of tracheal extubation predicts improved postoperative outcomes and late survival after cardiac surgery. We also evaluated the optimal timing of extubation and its association with better postoperative outcomes. METHODS: Between 2002 and 2006, 1164 patients underwent early tracheal extubation (<6 hours after surgery) and 1571 had conventional extubation (>6 hours after surgery). Propensity score adjustment and multivariable logistic regression analysis were used to adjust for imbalances in the patients' preoperative characteristics. Receiver operating characteristic curves (ROC) were used to identify the best timing of extubation and improved postoperative outcomes. Cox regression analysis was used to identify whether early extubation is a risk factor for decreased late mortality. RESULTS: Results - Early extubation was associated with lower propensity score-adjusted rate of operative mortality (Odds Ratio =0.55, 95% Confidence Intervals =0.31-0.98, p=0.043). Extubation within 9 hours emerged as the best predictor of improved postoperative morbidity and mortality (sensitivity =85.5%, specificity =52.7%, accuracy =64.5%). Early extubation also predicted decreased late mortality (Hazard Ratio =0.45, 95% Confidence Intervals 0.31-0.67, p<0.001). CONCLUSIONS: Early extubation may predict improved outcomes after cardiac surgery. Extubation within 9 hours after surgery was the best predictor of uncomplicated recovery after cardiac surgery. Those patients intubated longer than 16 hours have a poorer postoperative prognosis. Early extubation predicts prolonged survival up to 16 months after surgery.

Robotic Heller myotomy: a safe operation with higher postoperative quality-of-life indices.

INTRODUCTION: Achalasia is a primary motility disorder of the esophagus that is treated most effectively with operative myotomy. Excellent outcomes with laparoscopic myotomy and fundoplication are well known. Heller myotomy utilizing a computer-enhanced (robotic) laparoscopic platform allows for a more precise dissection by utilizing the superior optics of a 3-dimensional camera and greater degrees of freedom provided by robotic instrumentation. How this affects outcome and quality of life is unknown. METHODS: We assessed patients' health perceptions using a standardized, validated, health-related, disease-specific quality-of-life metric. Sixty-one consecutive patients undergoing laparoscopic or robotic myotomy over a 6-year period were evaluated prospectively. All operations were performed using intraoperative manometric and endoscopic guidance and all except 5 patients had a fundoplication. The effects of the operation on health-related quality of life were evaluated with the Short Form (SF-36) Health Status Questionnaire and a disease-specific gastroesophageal reflux disease activity (GERD) activity index (GRACI) preoperatively and postoperatively. All patients completed the questionnaire at both time points. Patient scores were compared using 2-way repeated measures analyses of variance followed by the Tukey test. Operative time, estimated blood loss, duration of stay, intraoperative complication, and postoperative complications were analyzed. RESULTS: Thirty-seven patients had laparoscopic and 24 patients had robotic Heller myotomy. There was an increase in SF-36 overall evaluation of health postoperatively compared with preoperatively in both groups (P < .05). The robotic myotomy patients had better SF-36 Role Functioning (emotional) and General Health Perceptions (P < .05) compared with the laparoscopic group. The GRACI showed an equivalent improvement in severity of symptoms in both groups (P < .05). Operative time was 287 +/- 9 minutes for laparoscopic cases and 355 +/- 23 minutes for robotic cases. Estimated blood loss and duration of stay were not different between groups. There were 3 operative esophageal perforations (8%) during laparoscopic myotomy and all were repaired immediately. There were no perforations or operative complications in the robotic group. Neither group had any additional complications. CONCLUSIONS: Minimally invasive operative myotomy improves functional status and overall evaluation of health in patients with achalasia. Robotic myotomy had no intraoperative esophageal perforations compared with an 8% intraoperative rate during laparoscopic myotomy. Heller myotomy with partial fundoplication using a robotic platform appears to be a more precise and safer operation than laparoscopic myotomy with improved quality-of-life indices postoperatively compared with laparoscopic myotomy with fewer complications; this suggests that, in skilled hands, the robotic platform may be safer, with improved quality-of-life outcomes.

Muscle fatigue during intermittent isokinetic shoulder abduction: age effects and utility of electromyographic measures.

Most existing evidence regarding the effects of age on muscular fatigue has focused on prolonged isometric contractions, repeated maximum dynamic contractions and individuals beyond traditional retirement age (>65 years). In the present study, age-related differences in muscle fatigue during submaximal dynamic efforts were examined. There were 24 younger (18-25 years) and 24 older (55-65 years) participants, all of whom were healthy and active, with equal numbers of each gender within each age group. Participants performed repetitive, intermittent shoulder abductions until exhaustion, at peak moments of 30% and 40% of individual maximum voluntary isokinetic contraction (MVIC) and with cycle durations of 20 and 40 s. Fatigue development was determined based on changes in MVIC, electromyographic (EMG) signals and ratings of perceived discomfort (RPD). Following the exhaustive exercises, strength recovery was monitored using a series of MVICs over a 15-min period. Results indicated the existence of an age-related fatigue resistance, with the older group demonstrating significantly slower rates of MVIC decline and RPD increase and smaller modifications in EMG-based fatigue measures. These age effects were generally more pronounced at the higher effort level. Main effects of effort level and cycle duration were also significant, while gender effects appeared to be marginal. Rates of strength recovery were not significantly influenced by age. In addition, the utility of standard EMG-based fatigue measures was assessed. Findings indicated that time-dependent changes in static and dynamic EMG-based measures were roughly comparable in terms of sensitivity and variability, supporting the use of standard EMG analyses for fatigue monitoring during intermittent dynamic contractions.

Muscle fatigue and endurance during repetitive intermittent static efforts: development of prediction models.

Localized muscle fatigue has received growing attention as a potential design variable and exposure metric in research towards prevention of musculoskeletal disorders in the workplace. While fatigue during sustained static work has been investigated extensively, effects during tasks comprising work-rest cycles are less clear. Work-rest models for static intermittent work have been presented in several reports, but the applicability is often limited to specific conditions. A study was conducted that facilitated a description of the relationships between static intermittent efforts and muscle endurance and fatigue. Exercises consisted of 1 h (maximum) of repetitive static arm abductions, involving a range of muscle contraction levels (10-30% maximum voluntary exertion), duty cycles (0.2-0.8) and cycle times (20-180 s). A between-subject central composite experimental design was used and 15 different exercise conditions were examined with six participants (three females and three males) for each. Along with endurance times, temporal changes related to fatigue were monitored using muscle strength, ratings of discomfort and electromyography (EMG) obtained from the middle-deltoid muscle during the contraction phase of the work cycles. The results of this study showed the influence of contraction level and duty cycle on the majority of fatigue measures used, while cycle time tended to affect EMG spectral measures. Using a response surface methodology, several fatigue prediction models and contour plots were developed that can be employed as an aid for design and evaluation of light repetitive static tasks. Good correspondence was generally found between discomfort rating and other measures of fatigue, suggesting the usefulness of this measure for rapid assessments of local fatigue in the workplace.

Effects of lumbar extensor fatigue and fatigue rate on postural sway.

Falls from heights resulting from a loss of balance are a major concern in the occupational setting. Previous studies have documented a deleterious effect of lower extremity fatigue on balance. The purpose of this study was to investigate the effect of lumbar extensor fatigue on balance during quiet standing. Additionally, the effects of fatigue rate on balance and balance recovery rate were assessed. Eight center-of-pressure-based measures of postural sway were collected from 13 participants, both before and after a protocol that fatigued the lumbar extensors to 60% of their unfatigued maximum voluntary exertion force. In addition, postural sway was measured for 30 min after the fatiguing protocol, at 5-min intervals, to quantify balance recovery rate during recovery from fatigue. Two different fatigue rates were achieved by fatiguing participants over either 10 min or 90 min. Results show an increase up to 58% in time-domain postural sway measures with lumbar extensor fatigue, but no change in frequency-domain measures. Fatigue rate did not affect the magnitude of these postural sway increases, nor did it affect the rate of balance recovery following fatigue. Statistical power for the latter result, however, was low. These results show that lumbar extensor fatigue increases postural sway and may contribute to fall-from-height accidents.

Breast cancer in patients with residual invasive carcinoma is more accurately staged with additive tumor size assessment.

BACKGROUND: Accurate assessment of tumor size for patients with breast cancer undergoing re-excision following breast-conserving therapy is important for appropriate staging and adjuvant treatment. We investigated the accuracy of additive vs. nonadditive size assessment in determining final tumor stage. METHODS: Patients with infiltrating carcinoma in the initial excision and in at least one additional re-excision (re-excision positive; n = 89) had tumor size assessed with additive and nonadditive techniques. This group was compared with patients undergoing re-excision but without identifiable residual carcinoma (re-excision negative; n = 105) regarding rates of lymph node (LN) metastasis. RESULTS: The re-excision positive patients had a different median final tumor size depending on the size assessment technique used (nonadditive: 1.8 cm; additive: 3.0 cm; P <.0001). Both groups of patients had a median tumor size consistent with T1c staging in nonadditive size assessment. However, re-excision positive patients had a significantly higher incidence of LN metastasis (P <.05) than did re-excision negative patients. Both groups were then separated into T1 and T2 stages and the LN metastasis rates were assessed. Compared with nonadditive size assessment, additive size assessment distributed re-excision positive patients into T stages whereby the LN metastasis rates more closely approximated those of re-excision negative patients (T1, 3% vs. 6% difference; T2, 4% vs. 13% difference). CONCLUSIONS: With regard to LN metastasis, staging for patients with residual invasive carcinoma in re-excision specimens is more accurate with additive tumor size assessment.

Determination of relative UV response factors for HPLC by use of a chemiluminescent nitrogen-specific detector.

Ultraviolet (UV) absorbance is the most widely used detection method for high-performance liquid chromatography (HPLC) separations. In pharmaceutical analysis, purity determinations often include quantitation of related impurities based on relative HPLC peak areas obtained at a specific wavelength. In order for this quantitation to accurately reflect weight percentages of impurities, the relative UV response factors (absorptivities) at the given wavelength must be known. In this work, we present a convenient method for determining relative UV response factors on-line, without isolation or purification of impurities, without standards, and without requiring known analyte concentrations. The procedure described makes use of a chemiluminescent nitrogen-specific HPLC detector (CLND) in conjunction with a UV detector. The CLND response is directly proportional to the number of moles of nitrogen in each eluting peak, and can, therefore, be used to determine relative amounts of each nitrogen-containing impurity present in the sample, provided the molecular formulas are known (e.g. from exact mass LC-MS). It is a simple matter, then, to determine the relative UV response factors from the UV area ratios obtained for the same sample. The feasibility and accuracy of this method is demonstrated for gradient HPLC separations of commercially available compounds of widely varying structures. Finally, the method's utility in obtaining accurate mass balance is demonstrated by application to photodegradation of nifedipine.

Long-term evaluation of extended thymectomy with anterior mediastinal dissection for myasthenia gravis.

BACKGROUND: Thymectomy for the treatment of myasthenia gravis (MG) is well established. The extent of resection, however, remains a source for debate. Outcomes for newer surgical techniques need to be compared to more extensive procedures. METHODS: A retrospective review was done of 64 consecutive patients who underwent transsternal thymectomy with extended anterior mediastinal dissection for MG between 1979 and 2000 and who were operated on by a single surgeon. RESULTS: Fifty-six patient charts were available, providing 58 operative procedures. Three patients had died of unrelated causes. The mean age of symptom onset was 36.0 +/- 2.5 years, with a mean duration of 3.3 +/- 0.5 years until surgery was undertaken. The mean length of follow-up was 6.8 +/- 0.8 years. Operative procedures were associated with a 10.3% major morbidity rate and no mortality. Drug-free remission was achieved in 50.0% of the patients, and symptoms were absent or improved in 76.8% of the patients. Patients followed up long-term (>10 years) achieved the greatest remission rate (71.4%) and symptomatic improvement (85.7%). After thymectomy, the mean dosages of prednisone and Mestinon decreased by 69.3% and 58.8%, respectively. CONCLUSIONS: Extended thymectomy provides excellent overall symptom improvement, which is enhanced over time. This review provides a basis for long-term comparison with other less invasive and perhaps less extensive procedures.

Intraoperative manometry to assess the esophagogastric junction during laparoscopic fundoplication and myotomy.

SUMMARY: Surgery for gastroesophageal reflux disease and achalasia is performed to alleviate symptoms by improving esophagogastric junction (EGJ) function. Intraoperative manometry was used to evaluate the pressure-length characteristics of the reconstructed EGJ during laparoscopic Nissen fundoplication and laparoscopic Heller myotomy. Intraoperative manometry was performed in 37 consecutive patients undergoing laparoscopic Nissen fundoplication (n = 22) or laparoscopic Heller myotomy (n = 15). Measurements were taken before surgery, after creation of the pneumoperitoneum, after completion of the myotomy in achalasia, and after creation of the fundoplication. Tracings were analyzed for pressure, length, and the integrated pressure-length relation (area under the curve [AUC]). Statistical comparison was made using paired t tests; intraoperative EGJ measurements did not correlate well with preoperative values for either pressure or length. Laparoscopic Nissen fundoplication significantly increased pressure, length, and AUC of the EGJ compared with prefundoplication values. Laparoscopic Heller myotomy significantly decreased EGJ pressure, length, and AUC. Creation of a Toupet fundoplication after myotomy did not significantly increase pressure, length, and AUC of the EGJ compared with postmyotomy values. Intraoperative manometry identified 2 of 15 achalasia patients (13%) with persistent areas of high pressure after initial myotomy that were corrected by extending the myotomy. Intraoperative manometry identifies mechanical changes created during EGJ surgery and may be a useful adjunct to improve outcomes of laparoscopic Nissen fundoplication and laparoscopic Heller myotomy.

Static and dynamic myoelectric measures of shoulder muscle fatigue during intermittent dynamic exertions of low to moderate intensity.

Despite extensive research on muscular fatigue during prolonged static efforts, there have been relatively few studies of more complex tasks (dynamic and intermittent). A laboratory study of overhead work tasks was conducted to investigate whether electromyographic (EMG) measures can potentially serve as indicators of fatigue, particularly for ergonomic tasks analysis. Sixteen participants performed the tasks until they either developed substantial discomfort or reached a 3-h limit. EMG signals were obtained at intervals throughout the experiment from four shoulder muscles, both statically (during fixed-level test contractions) and dynamically (during task performance). Both EMG root mean square (RMS) amplitude and spectral content (mean and median power frequencies) were examined and compared in terms of their variability and sensitivity. In addition, a new fatigue index was developed to allow for the estimation of substantial fatigue onset. Variability was found to differ significantly between muscles and EMG measures, and was generally lowest for mean power frequencies obtained during static test contractions. Sensitivity was typically greatest for RMS versus spectral measures, and slightly higher for median than mean power frequencies. The results suggest that fatigue during dynamic tasks, while a complex phenomenon, can be monitored and quantified using EMG.

Fatigue and endurance limits during intermittent overhead work.

Shoulder problems are prevalent in industrial work, particularly when tasks require the hands to be used at or above shoulder level. Although extensive research has been conducted on prolonged static exertions, and several guidelines for such efforts exist, there is insufficient information for ergonomic evaluation of tasks that are intermittent and/or dynamic. A laboratory simulation was conducted of overhead assembly work that was both intermittent and dynamic, and which varied the duty cycle (work/rest ratio), arm reach, and hand orientation of a tapping task. Results consisted of endurance times and also the times of fatigue onset as indicated by perceived discomfort and declines in muscle strength. Females exhibited longer (22%) endurance times, delayed reports of discomfort, and slower declines in strength. Significant influences of duty cycle were found on both endurance and fatigue times, yet arm reach and hand orientation did not have consistent effects. Distributions of endurance and fatigue times are presented as criteria for preliminary evaluation of overhead work. Endurance times could be predicted with only moderate accuracy from earlier indicators of fatigue onset. Existing guidelines, albeit developed for static tasks, appeared unsuitable for the simulated overhead assembly efforts examined. Furthermore, such guidelines may fail to capture the substantial interindividual variability observed in this experiment.

Evaluation of endoscopic and laparoscopic training practices in surgical residency programs.

BACKGROUND: The ability to adequately train surgical residents in flexible and rigid endoscopy has become a difficult challenge for program directors. The American Board of Surgery requires residents to be familiar in these procedures but the methods for training have not been well defined nor formally outlined. The goals of this study were to evaluate resident experience in flexible endoscopy and laparoscopy and to investigate the specific methods used by surgical programs for the training of residents. METHODS: A survey was created by the authors and the Resident Education Committee of the Society of American Gastrointestinal Endoscopic Surgeons and was mailed to all program directors in general surgery in the United States based on the data base of the Association of Program Directors in Surgery (APDS). RESULTS: Ninety-six of 283 surveys were returned (33.9%). The surgeon played a greater role in flexible endoscopic training in 1998 as compared to 1988 (p=0.002). When analyzed by type of institution, community programs showed a similar trend but this was not seen in academic programs. Formal endoscopy rotations existed in 60% of programs but flexible endoscopy (5.2%) and laparoscopy (10.4%) fellowships were uncommon. No significant differences in the number of advanced laparoscopic procedures performed were found between academic and community programs. The presence of a laparoscopic fellow did not significantly decrease the number of cases per resident. CONCLUSION: According to our survey, surgery departments have a greater impact on flexible endoscopic training in 1998 than in 1988. This is likely due to the creation of formal endoscopy rotations and the hiring of fellowship trained endoscopic instructors. In addition, community programs have been able to provide adequate experience in both basic and advanced laparoscopic techniques as compared to academic programs. As with flexible endoscopy, however, formal laparoscopic rotations may be necessary to allow more intensive experience for each resident.

Motion times, hand forces, and trunk kinematics when using material handling manipulators in short-distance transfers of moderate mass objects.

The risk of musculoskeletal injury associated with manual materials handling tasks has led in part to the use of material handling manipulators, yet there is limited empirical data to facilitate selection, design, and evaluation of these devices. A laboratory study of two types of mechanical manipulators (articulated arm and overhead hoist) was conducted of short-distance transfers of moderate loads, and the influence of various task parameters and transfer method on motion times, peak hand forces, and torso kinematics was obtained. Use of manipulators increased elemental motion times for symmetric sagittal plane transfers by 36-63%, and asymmetric transfers (in the frontal plane) by 62-115%, compared to similar transfers performed manually. Peak hand forces were significantly lower with both manipulators (40-50%), and approximately 10% higher for asymmetric versus symmetric transfers. Overall torso kinematics were grossly similar with and without a manipulator. These results suggest that for self-paced job tasks, moderate mass objects will be transferred slower over short distances and with lower levels of external (hand) forces when using mechanical aids. These simple effects, however, were influenced by object mass and transfer height.

Back lift versus leg lift: an index and visualization of dynamic lifting strategies.

The description of a lifting strategy is typically provided in qualitative terms. A quantitative static descriptor or index differentiates the starting postures but not the primary moving segments. This technical note proposes an index that quantitatively characterizes different dynamic postural strategies employed during sagittal plane lifting. Dynamic lifting strategies are modeled in the velocity domain as different schemes of partitioning postural changes between the torso and leg segments. The index consists of two parameters, assigned to two leg segments, quantifying their contributions relative to the torso. Given a measured lifting movement, its index parameters values, ranging from 0.1 to 10, are estimated through an enumeration search process with the objective of minimizing the fitting error. The use of this index is illustrated by applying it to 24 lifting movements performed by six subjects assuming either a back-lift or a leg-lift strategy. Results indicate that a lifting strategy, in terms of whether the leg or the back is generally the prime mover, can be differentiated and visualized using this simple two-parameter index. In addition, indistinct intermediate strategies are also discerned, as the involvement of each segment in a lifting movement is quantified. The index is however limited in that it does not accommodate arm motion contributions to a lift nor possible time-dependent strategic changes during a lift. Potential future applications include time-efficient movement prediction and simulation for computerized biomechanical or ergonomic analysis.

The determination of oxalic acid, oxamic acid, and oxamide in a drug substance by ion-exclusion chromatography.

Oxalic acid, oxamic acid and oxamide are potential impurities in some active pharmaceutical ingredients (API). The retention and separation of oxalic and oxamic acids are particularly challenging using conventional reversed-phase HPLC due to their high polarity. An ion-exclusion chromatography (IEC) method has been shown to provide good separation and sensitivity for the three oxalate-related impurities in a hydrophobic API matrix. The method uses a Dionex IonPac ICE-ASI column with 95/5 (v/v) 0.1% sulfuric acid/acetonitrile as the mobile phase and UV detection at 205 nm. Development and validation of this method are described.