The purpose of this paper is to empirically investigate the relationship between lean production implementation and financial performance. Particular emphasis is placed on the mediating role of ...inventory leanness in deriving the financial performance benefits commonly associated with lean production. Moreover, the interaction among different lean practice bundles in affecting financial and inventory performance is assessed. Based on an analysis of a combination of survey and secondary data, the effect of lean production on financial performance is found to be partially mediated by inventory leanness. In addition, there is strong evidence that the concurrent implementation of internally-focused and externally-focused lean practices yields greater performance benefits than selective lean production implementation. Thus, this study contributes to the theory of lean production by providing insights into the mediated and moderated effects of lean production on inventory leanness and financial performance.
► We investigate the relationship between lean production, inventories and performance. ► The empirical analysis is based on survey and secondary data from US manufacturing firms. ► The effect of lean production on performance is partially mediated by inventory leanness. ► The concurrent implementation of lean practice bundles yields greater performance benefits.
This paper adds to the empirical inventory management literature by examining the moderating effects of environmental dynamism on the relationship between inventory leanness and financial ...performance. While the financial implications of inventory management practices have been extensively studied in the literature, it is clear that lean inventory strategies may not have the same payoff for all firms in all industries. Grounded in inventory theory, this study explores how firm characteristics and environmental dynamism—measured in terms of innovative intensity, demand uncertainty and competitive intensity—moderate the inventory leanness–performance link. We use hierarchical linear modeling to analyze a data set of 5749 firm-year observations from 123 U.S. manufacturing industries. In line with the hypotheses set forth, the results indicate that innovative intensity in an industry increases the effect of inventory leanness on firm performance while competitive intensity has the opposite effect. The hypothesis with respect to the moderating role of demand uncertainty is not supported. Another interesting and important finding is that inventory leanness accounts for nearly one third of the variation in firm performance after controlling for firm size and growth, thus underlining the importance of efficient and effective inventory management for overall firm success.
Summary Background Brachial plexus injuries can permanently impair hand function, yet present surgical reconstruction provides only poor results. Here, we present for the first time bionic ...reconstruction; a combined technique of selective nerve and muscle transfers, elective amputation, and prosthetic rehabilitation to regain hand function. Methods Between April 2011, and May 2014, three patients with global brachial plexus injury including lower root avulsions underwent bionic reconstruction. Treatment occurred in two stages; first, to identify and create useful electromyographic signals for prosthetic control, and second, to amputate the hand and replace it with a mechatronic prosthesis. Before amputation, the patients had a specifically tailored rehabilitation programme to enhance electromyographic signals and cognitive control of the prosthesis. Final prosthetic fitting was applied as early as 6 weeks after amputation. Findings Bionic reconstruction successfully enabled prosthetic hand use in all three patients. After 3 months, mean Action Research Arm Test score increased from 5·3 (SD 4·73) to 30·7 (14·0). Mean Southampton Hand Assessment Procedure score improved from 9·3 (SD 1·5) to 65·3 (SD 19·4). Mean Disabilities of Arm, Shoulder and Hand score improved from 46·5 (SD 18·7) to 11·7 (SD 8·42). Interpretation For patients with global brachial plexus injury with lower root avulsions, who have no alternative treatment, bionic reconstruction offers a means to restore hand function. Funding Austrian Council for Research and Technology Development, Austrian Federal Ministry of Science, Research & Economy, and European Research Council Advanced Grant DEMOVE.
We compared the behavior of motor neurons innervating their physiological muscle targets with motor neurons from the same spinal segment whose axons were surgically redirected to remnant muscles ...(targeted muscle reinnervation). The objective was to assess whether motor neurons with nonphysiological innervation receive similar synaptic input and could be voluntary controlled as motor neurons with natural innervation. For this purpose, we acquired high-density EMG signals from the biceps brachii in 5 male transhumeral amputees who underwent targeted reinnervation of this muscle by the ulnar nerve and from the first dorsal interosseous muscle of 5 healthy individuals to investigate the natural innervation of the ulnar nerve. The same recordings were also performed from the biceps brachii muscle of additional 5 able-bodied individuals. The EMG signals were decomposed into discharges of motor unit action potentials. Motor neurons were progressively recruited for the full range of submaximal muscle activation in all conditions. Moreover, their discharge rate significantly increased from recruitment to target activation level in a similar way across the subject groups. Motor neurons across all subject groups received common synaptic input as identified by coherence analysis of their spike trains. However, the relative strength of common input in both the delta (0.5-5 Hz) and alpha (5-13 Hz) bands was significantly smaller for the surgically reinnervated motor neuron pool with respect to the corresponding physiologically innervated one. The results support the novel approach of motor neuron interfacing for prosthesis control and provide new insights into the role of afferent input on motor neuron activity.
Targeted muscle reinnervation surgically redirects nerves that lost their target in the amputation into redundant muscles in the region of the stump. The study of the behavior of motor neurons following this surgery is needed for designing biologically inspired prosthetic control strategies. Moreover, targeted muscle reinnervation offers a human experimental framework for studying the control and behavior of motor neurons when changing their target innervated muscle fibers and sensory feedback. Here, we show that the control of motor neurons and their synaptic input, following reinnervation, was remarkably similar to that of the physiological innervation, although with reduced common drive at some frequencies. The results advance our knowledge on the role of sensory input in the generation of the neural drive to muscles and provide the basis for designing physiologically inspired methods for prosthesis control.
Wrist-worn consumer-grade activity trackers are popular devices, developed mainly for personal use. This study aimed to explore the validity, reliability and sensitivity to change of movement ...behaviors metrics from three activity trackers (Polar Vantage M, Garmin Vivoactive 4s and Garmin Vivosport) in controlled and free-living conditions when worn by older adults. Participants (n = 28; 74 ± 5 years) underwent a videotaped laboratory protocol while wearing all three trackers. On a separate occasion, participants (n = 17 for each of the trackers) wore one (randomly assigned) tracker and a research-grade activity monitor ActiGraph wGT3X-BT simultaneously for six consecutive days. Both Garmin trackers showed excellent performance for step counts, with a mean absolute percentage error (MAPE) below 20% and intraclass correlation coefficient (ICC
) above 0.90 (
< 0.05). The MAPE for sleep time was within 10% for all the trackers tested, while it was far beyond 20% for all other movement behaviors metrics. The results suggested that all three trackers could be used for measuring sleep time with a high level of accuracy, and both Garmin trackers could also be used for step counts. All other output metrics should be used with caution. The results provided in this study could be used to guide choice on activity trackers aiming for different purposes-individual use, longitudinal monitoring or in clinical trial setting.
Reliable force control is especially important when using myoelectric upper-limb prostheses as the force defines whether an object will be firmly grasped, damaged, or dropped. It is known from human ...motor control that the grasping of able-bodied subjects is based on a combination of anticipation and feedback correction. Inspired by this insight, the present study proposes a novel approach to provide artificial sensory feedback to the user of a myoelectric prosthesis using vibrotactile stimulation to facilitate both predictive and corrective processes characteristic of grasping in able-bodied people. Specifically, the level of EMG was conveyed to the subjects while closing the prosthesis (predictive strategy), whereas the actual grasping force was transmitted when the prosthesis closed (corrective strategy). To investigate if this combined EMG and force feedback is indeed an effective method to explicitly close the control loop, 16 able-bodied and 3 transradial amputee subjects performed a set of functional tasks, inspired by the "Box and Block" test, with six target force levels, in three conditions: no feedback, only EMG feedback, and combined feedback. The highest overall performance in able-bodied subjects was obtained with combined feedback (79.6±9.9%), whereas the lowest was achieved with no feedback (53±11.5%). The combined feedback, however, increased the task completion time compared to the other two conditions. A similar trend was obtained also in three amputee subjects. The results, therefore, indicate that the feedback inspired by human motor control is indeed an effective approach to improve prosthesis grasping in realistic conditions when other sources of feedback (vision and audition) are not blocked.
Influenza viruses cause acute respiratory disease of great importance to public health. Alveolar type II (ATII) respiratory epithelial cells are central to normal lung function and are a site of ...influenza A virus replication in the distal lung. However, the consequences of infection for ATII cell function are poorly understood. To determine the impact of influenza infection on ATII cells we used C57BL/6-congenic SP-C(GFP) mice that express green fluorescent protein (GFP) under the control of the surfactant protein-C (SP-C) promoter, which is only active in ATII cells. Most cells isolated from the lungs of uninfected SP-C(GFP) mice were GFP(+) but did not express the alveolar type I (ATI) antigen podoplanin (PODO). ATII cells were also EpCAM(+) and α2,3-linked sialosaccharide(+). Infection with influenza A/WSN/33 virus caused severe hypoxemia and pulmonary edema. This was accompanied by loss of whole lung GFP fluorescence, reduced ATII cell yields, increased ATII cell apoptosis, reduced SP-C gene and protein expression in ATII cell lysates, and increased PODO gene and protein levels. Flow cytometry indicated that infection decreased GFP(+)/PODO(-) cells and increased GFP(-)/PODO(+) and GFP(-)/PODO(-) cells. Very few GFP(+)/PODO(+) cells were detectable. Finally, infection resulted in a significant decline in EpCAM expression by PODO(+) cells, but had limited effects on α2,3-linked sialosaccharides. Our findings indicate that influenza infection results in a progressive differentiation of ATII cells into ATI-like cells, possibly via an SP-C(-)/PODO(-) intermediate, to replace dying or dead ATI cells. However, impaired SP-C synthesis is likely to contribute significantly to reduced lung compliance in infected mice.
The level of sustainable excitability within lumbar spinal cord circuitries is one of the factors determining the functional outcome of locomotor therapy after motor‐incomplete spinal cord injury. ...Here, we present initial data using noninvasive transcutaneous lumbar spinal cord stimulation (tSCS) to modulate this central state of excitability during voluntary treadmill stepping in three motor‐incomplete spinal cord‐injured individuals. Stimulation was applied at 30 Hz with an intensity that generated tingling sensations in the lower limb dermatomes, yet without producing muscle reflex activity. This stimulation changed muscle activation, gait kinematics, and the amount of manual assistance required from the therapists to maintain stepping with some interindividual differences. The effect on motor outputs during treadmill‐stepping was essentially augmentative and step‐phase dependent despite the invariant tonic stimulation. The most consistent modification was found in the gait kinematics, with the hip flexion during swing increased by 11.3° ± 5.6° across all subjects. This preliminary work suggests that tSCS provides for a background increase in activation of the lumbar spinal locomotor circuitry that has partially lost its descending drive. Voluntary inputs and step‐related feedback build upon the stimulation‐induced increased state of excitability in the generation of locomotor activity. Thus, tSCS essentially works as an electrical neuroprosthesis augmenting remaining motor control.
While firms increasingly adopt lean inventory practices, there is limited evidence that inventory leanness leads to improved firm performance. This study reexamines this relationship in an attempt to ...overcome some shortcomings of previous research. To that end, a theory-based measure of inventory leanness, which takes into account industry-specific inventory management characteristics, is proposed. The analysis of a large panel data set of U.S. manufacturing companies reveals that the significance and shape of the inventory–performance relationship varies substantially across industries. This relationship is significant in two-thirds of the 54 industries studied. In most of these instances, the relationship is concave, suggesting that there is an optimum level of inventory leanness beyond which firm performance deteriorates. A post-hoc analysis is conducted to identify industry-level characteristics that may determine the nature the inventory–performance relationship. Managerial implications are discussed and several opportunities for future research are outlined.
Falls are a major cause of injury and morbidity in older adults. To reduce the incidence of falls, a systematic assessment of the risk of falling is of paramount importance. The purpose of this ...systematic review was to provide a comprehensive comparison of the diagnostic balance tests used to predict falls and for distinguishing older adults with and without a history of falls. We conducted a systematic review of the studies in which instrumented (force plate body sway assessment) or other non-instrumented balance tests were used. We analyzed the data from 19 prospective and 48 retrospective/case-control studies. Among the non-instrumented tests, the single-leg stance test appears to be the most promising for discrimination between fallers and non-fallers. In terms of body sway measures, the center-of-pressure area was most consistently associated with falls. No evidence was found for increased benefit of the body sway test when cognitive tasks were added, or the vision was eliminated. While our analyses are limited due to the unbalanced representation of different test and outcome measures across studies, we can recommend the single-leg test for the assessment of the risk of falling, and the measurements of body sway for a more comprehensive assessment.
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