In situ disordering of monoclinic titanium monoxide Ti5O5 studied by transmission electron microscope TEM.

The superlattice and domain structures exhibited by ordered titanium monoxide Ti5O5 are disrupted by low energy electron beam irradiation. The effect is attributed to the disordering of the oxygen and titanium sublattices. This disordering is caused by the displacement of both oxygen and titanium atoms by the incident electrons and results in a phase transformation of the monoclinic phase Ti5O5 into cubic B1 titanium monoxide. In order to determine the energies required for the displacement of titanium or oxygen atoms, i.e. threshold displacement energies, a systematic study of the disappearance of superstructure reflections with increasing electron energy and electron bombardment dose has been performed in situ in a transmission electron microscope (TEM). An incident electron energy threshold between 120 and 140 keV has been observed. This threshold can be ascribed to the displacements of titanium atoms with 4 as well as with 5 oxygen atoms as nearest neighbors. The displacement threshold energy of titanium atoms in Ti5O5 corresponding with the observed incident electron threshold energy lies between 6.0 and 7.5 eV. This surprisingly low value can be explained by the presence of either one or two vacant oxygen lattice sites in the nearest neighbors of all titanium atoms.

Effectiveness of workplace interventions in the prevention of upper extremity musculoskeletal disorders and symptoms: an update of the evidence.

The burden of disabling musculoskeletal pain and injuries (musculoskeletal disorders, MSDs) arising from work-related causes in many workplaces remains substantial. There is little consensus on the most appropriate interventions for MSDs. Our objective was to update a systematic review of workplace-based interventions for preventing and managing upper extremity MSD (UEMSD). We followed a systematic review process developed by the Institute for Work & Health and an adapted best evidence synthesis. 6 electronic databases were searched (January 2008 until April 2013 inclusive) yielding 9909 non-duplicate references. 26 high-quality and medium-quality studies relevant to our research question were combined with 35 from the original review to synthesise the evidence on 30 different intervention categories. There was strong evidence for one intervention category, resistance training, leading to the recommendation: Implementing a workplace-based resistance training exercise programme can help prevent and manage UEMSD and symptoms. The synthesis also revealed moderate evidence for stretching programmes, mouse use feedback and forearm supports in preventing UEMSD or symptoms. There was also moderate evidence for no benefit for EMG biofeedback, job stress management training, and office workstation adjustment for UEMSD and symptoms. Messages are proposed for both these and other intervention categories.

In vivo flexor tendon forces generated during different rehabilitation exercises.

UNLABELLED: We measured in vivo forces in the flexor digitorum profundus and the flexor digitorum superficialis tendons during commonly used rehabilitation manoeuvres after flexor tendon repair by placing a buckle force transducer on the tendons of the index finger in the carpal canal during open carpal tunnel release of 12 patients. We compared peak forces for each manoeuvre with the reported strength of a flexor tendon repair. Median flexor digitorum profundus force (24 N) during isolated flexor digitorum profundus flexion and median flexor digitorum superficialis force (13 N) during isolated flexor digitorum superficialis flexion were significantly higher than during the other manoeuvres. Significantly higher median forces were observed in the flexor digitorum superficialis with the wrist at 30° flexion (6 N) compared with the neutral wrist position (5 N). Median flexor digitorum profundus forces were significantly higher during active finger flexion (6 N) compared with place and hold (3 N). Place and hold and active finger flexion with the wrist in the neutral position or tenodesis generated the lowest forces; isolated flexion of these tendons generated higher forces along the flexor tendons. LEVEL OF EVIDENCE: III (controlled trial without randomization).

Prevención de síntomas visuales y músculo-esqueléticos asociados al uso de ordenador en el trabajo / Workplace interventions to prevent musculoskeletal and visual symptoms and disorders among computer users: A systematic review

Antecedentes: La literatura científica sobre el efecto de las intervenciones en el puesto de trabajo, en la compensación de un defecto refractivo y en la conducta sobre los síntomas músculo-esqueléticos y visuales en los usuarios de ordenador, es amplia y heterogénea. Método: Se realizó una revisión sistemática de la literatura como la mejor síntesis de la evidencia para abordar la siguiente cuestión general: ¿Tienen las intervenciones en trabajadores de oficina que son usuarios de ordenador un efecto sobre la salud músculo-esquelética o visual? También se realizó una evaluación de intervenciones específicas. Resultados: La búsqueda inicial identificó 7.313 artículos que se redujeron a 31 estudios tras analizar contenido y calidad. En general, se observó un nivel mixto de evidencia para la pregunta general. Se observó una evidencia moderada de que: (1) la adaptación de los puestos de trabajo no tenía ningún efecto, (2) tampoco la realización de descansos y ejercicio y (3) utilizar dispositivos alternativos a los ratones convencionales sí tenía un efecto positivo. Para el resto de intervenciones se observó una evidencia del efecto mixta o insuficiente. Conclusión: Se encontraron pocos estudios de alta calidad que examinaran los efectos de las intervenciones en oficinas sobre los problemas musculo-esqueléticos y de la salud visual

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A randomised controlled trial evaluating an alternative mouse and forearm support on upper body discomfort and musculoskeletal disorders among engineers.

OBJECTIVES: The aim of this intervention study was to determine the effects of an alternative mouse and/or a forearm support board on the change in upper body discomfort scores and the development of incident musculoskeletal disorders. METHODS: This randomised controlled intervention trial followed 206 engineers for one year. Participants were randomised to receive (1) a conventional mouse only, (2) an alternative mouse only, (3) a forearm support board, or (4) an alternative mouse plus forearm support board. Outcome measures included weekly upper body discomfort scores and incident musculoskeletal disorders. RESULTS: During the study, 42 participants were diagnosed with an incident musculoskeletal disorder. The group that received the forearm support board experienced a reduction in their right upper extremity discomfort (beta-coefficient -0.35, 95% CI -0.67 to -0.03) in comparison to those who did not receive a forearm board. The group that received the alternative mouse had a protective, but non-significant (p = 0.20), effect on incident cases of right upper extremity musculoskeletal disorders (HR 0.57, 95% CI 0.24 to 1.34) and a non-significant reduction in neck/shoulder discomfort (beta-coefficient -0.23, 95% CI -0.056 to 0.10) in comparison to those who received a conventional mouse. CONCLUSIONS: In engineers who use a computer for more than 20 h per week, a forearm support board may reduce right upper extremity discomfort attributed to computer use.

Work-organisational and personal factors associated with upper body musculoskeletal disorders among sewing machine operators.

OBJECTIVE: To assess the contribution of work-organisational and personal factors to the prevalence of work-related musculoskeletal disorders (WMSDs) among garment workers in Los Angeles. METHODS: This is a cross-sectional study of self-reported musculoskeletal symptoms among 520 sewing machine operators from 13 garment industry sewing shops. Detailed information on work-organisational factors, personal factors, and musculoskeletal symptoms were obtained in face-to-face interviews. The outcome of interest, upper body WMSD, was defined as a worker experiencing moderate or severe musculoskeletal pain. Unconditional logistic regression models were adopted to assess the association between both work-organisational factors and personal factors and the prevalence of musculoskeletal pain. RESULTS: The prevalence of moderate or severe musculoskeletal pain in the neck/shoulder region was 24% and for distal upper extremity it was 16%. Elevated prevalence of upper body pain was associated with age less than 30 years, female gender, Hispanic ethnicity, being single, having a diagnosis of a MSD or a systemic illness, working more than 10 years as a sewing machine operator, using a single sewing machine, work in large shops, higher work-rest ratios, high physical exertion, high physical isometric loads, high job demand, and low job satisfaction. CONCLUSION: Work-organisational and personal factors were associated with increased prevalence of moderate or severe upper body musculoskeletal pain among garment workers. Owners of sewing companies may be able to reduce or prevent WMSDs among employees by adopting rotations between different types of workstations thus increasing task variety; by either shortening work periods or increasing rest periods to reduce the work-rest ratio; and by improving the work-organisation to control psychosocial stressors. The findings may guide prevention efforts in the garment sector and have important public health implications for this workforce of largely immigrant labourers.

A randomised controlled trial evaluating the effects of two workstation interventions on upper body pain and incident musculoskeletal disorders among computer operators.

BACKGROUND: Call centre work with computers is associated with increased rates of upper body pain and musculoskeletal disorders. METHODS: This one year, randomised controlled intervention trial evaluated the effects of a wide forearm support surface and a trackball on upper body pain severity and incident musculoskeletal disorders among 182 call centre operators at a large healthcare company. Participants were randomised to receive (1) ergonomics training only, (2) training plus a trackball, (3) training plus a forearm support, or (4) training plus a trackball and forearm support. Outcome measures were weekly pain severity scores and diagnosis of incident musculoskeletal disorder in the upper extremities or the neck/shoulder region based on physical examination performed by a physician blinded to intervention. Analyses using Cox proportional hazard models and linear regression models adjusted for demographic factors, baseline pain levels, and psychosocial job factors. RESULTS: Post-intervention, 63 participants were diagnosed with one or more incident musculoskeletal disorders. Hazard rate ratios showed a protective effect of the armboard for neck/shoulder disorders (HR = 0.49, 95% CI 0.24 to 0.97) after adjusting for baseline pain levels and demographic and psychosocial factors. The armboard also significantly reduced neck/shoulder pain (p = 0.01) and right upper extremity pain (p = 0.002) in comparison to the control group. A return-on-investment model predicted a full return of armboard and installation costs within 10.6 months. CONCLUSION: Providing a large forearm support combined with ergonomic training is an effective intervention to prevent upper body musculoskeletal disorders and reduce upper body pain associated with computer work among call centre employees.

Cyclical articular joint loading leads to cartilage thinning and osteopontin production in a novel in vivo rabbit model of repetitive finger flexion.

OBJECTIVE: An in vivo rabbit model of repetitive joint flexion and loading was used to characterize the morphological effects of cyclical loading on articular cartilage. DESIGN: The forepaw digits of eight anesthetized New Zealand White adult female rabbits were repetitively flexed at 1 Hz with a mean peak digit load of 0.42 N for 2 h per day for 60 cumulative hours. Metacarpophalangeal joints were collected from loaded and contra-lateral control limbs, fixed, decalcified, embedded, and thin-sectioned. Serial sections were stained for histology or for immunohistochemistry. Morphometric data including the mean thicknesses of the uncalcified cartilage and of the calcified cartilage were collected from digital photomicrographs of safranin O-stained sections. The number of cells stained with anti-osteopontin antibody was counted. RESULTS: We observed a decrease in uncalcified cartilage mean thickness with no significant change in calcified cartilage thickness. We also observed a significant increase in the number of cells positive for osteopontin (OPN) in the uncalcified cartilage. These changes occurred without overt cartilage surface degeneration. CONCLUSIONS: Cyclical loading leads to changes at the tissue and cellular levels in articular cartilage. These changes are suggestive of tidemark advancement and may indicate a reactivation of cartilage mineralization steps analogous to endochondral ossification. This novel in vivo rabbit model of repetitive flexion and loading can be used to investigate the effects of cyclical loading on articular joints.

Influence of time pressure and verbal provocation on physiological and psychological reactions during work with a computer mouse.

The overall aim of this study was to investigate whether time pressure and verbal provocation has any effect on physiological and psychological reactions during work with a computer mouse. It was hypothesised that physiological reactions other than muscle activity (i.e. wrist movements, forces applied to the computer mouse) would not be affected when working under stressful conditions. Fifteen subjects (8 men and 7 women) participated, performing a standardised text-editing task under stress and control conditions. Blood pressure, heart rate, heart rate variability, electromyography, a force-sensing computer mouse and electrogoniometry were used to assess the physiological reactions of the subjects. Mood ratings and ratings of perceived exertion were used to assess their psychological reactions. The time pressure and verbal provocation (stress situation) resulted in increased physiological and psychological reactions compared with the two control situations. Heart rate, blood pressure and muscle activity in the first dorsal interosseus, right extensor digitorum and right trapezius muscles were greater in the stress situation. The peak forces applied to the button of the computer mouse and wrist movements were also affected by condition. Whether the increases in the physiological reactions were due to stress or increased speed/productivity during the stress situation is discussed. In conclusion, work with a computer mouse under time pressure and verbal provocation (stress conditions) led to increased physiological and psychological reactions compared to control conditions.

Determination of photomodified oligodeoxynucleotides by exonuclease digestion, matrix-assisted laser desorption/ionization and post-source decay mass spectrometry.

A fast method to detect and sequence photomodified oligodeoxynucleotides (ODNs) by exonuclease digestion and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) is reported. Upon treatment of modified ODNs with both phosphodiesterase I and phosphodiesterase II, the digestion stops at the sites of photomodification. Post-source decay (PSD) of MALDI-produced ions from two enzymatic digestion end products distinguishes isomers such as 5'-d(T[cis-syn]TAAGC) and 5'-d(CGAAT[cis-syn]T), which have symmetrical or identical compositions at the 3' and 5' ends, respectively. Studies have also been done to follow the kinetics for enzyme degradation of photomodified ODNs. The calculated rate constants from a mathematical treatment of the time-dependent MALDI data clearly show that the enzymatic digestion rate slows as the enzyme approaches the modified site.

Matrix-assisted laser desorption/ionization mass spectrometry for locating abasic sites and determining the rates of enzymatic hydrolysis of model oligodeoxynucleotides.

A method using a combination of exonuclease enzymatic digestion and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry was developed to locate model abasic sites in a series of model 21-base oligodeoxynucleotides in which a nucleobase was replaced by a hydrogen atom. The exonuclease digestion rate, with either snake venom phosphodiesterase (SVP) or bovine spleen phosphodiesterase (BSP), clearly slows as the digestion approaches the abasic sites and stops as it reaches it. An oligodeoxynucleotide containing an abasic site in which OH replaces the nucleobase shows similar results. MALDI mass spectra taken at appropriate times during the course of hydrolysis are the basis for rate measurements, and the kinetics also reveal the location of the abasic site. A mathematical treatment of the time-dependent MALDI data was implemented to obtain rate curves and rate constants for the enzymatic digestion of both modified and unmodified oligodeoxynucleotides.

Ischemia causes muscle fatigue.

The purpose of this investigation was to determine whether ischemia, which reduces oxygenation in the extensor carpi radialis (ECR) muscle, causes a reduction in muscle force production. In eight subjects, muscle oxygenation (TO2) of the right ECR was measured noninvasively and continuously using near infrared spectroscopy (NIRS) while muscle twitch force was elicited by transcutaneous electrical stimulation (1 Hz, 0.1 ms). Baseline measurements of blood volume, muscle oxygenation and twitch force were recorded continuously, then a tourniquet on the upper arm was inflated to one of five different pressure levels: 20, 40, 60 mm Hg (randomized order) and diastolic (69 +/- 9.8 mm Hg) and systolic (106 +/- 12.8 mm Hg) blood pressures. Each pressure level was maintained for 3-5 min, and was followed by a recovery period sufficient to allow measurements to return to baseline. For each respective tourniquet pressure level, mean TO2 decreased from resting baseline (100% TO2) to 99 +/- 1.2% (SEM), 96 +/- 1.9%, 93 +/- 2.8%, 90 +/- 2.5%, and 86 +/- 2.7%, and mean twitch force decreased from resting baseline (100% force) to 99 +/- 0.7% (SEM), 96 +/- 2.7%, 93 +/- 3.1%, 88 +/- 3.2%, and 86 +/- 2.6%. Muscle oxygenation and twitch force at 60 mm Hg tourniquet compression and above were significantly lower (P < 0.05) than baseline value. Reduced twitch force was correlated in a dose-dependent manner with reduced muscle oxygenation (r = 0.78, P < 0.001). Although the correlation does not prove causation, the results indicate that ischemia leading to a 7% or greater reduction in muscle oxygenation causes decreased muscle force production in the forearm extensor muscle. Thus, ischemia associated with a modest decline in TO2 causes muscle fatigue.

The effects of reduced oxygen tension on cell proliferation and matrix synthesis in synovium and tendon explants from the rabbit carpal tunnel: an experimental study in vitro.

Local ischemia may play an important role in the development of tendon degeneration as well as entrapment neuropathies. In order to investigate the cellular effects of hypoxia on tendon and synovial tissue from the carpal canal, dose response effects of oxygen on cell proliferation and synthesis of matrix components were examined in segments of synovial and flexor digitorum profundus tendon from the carpal tunnel of rabbits during short term culture. Explants were incubated in airtight containers flushed with either 0%, 1%, 3%, 20% O2 plus 2% CO2 and N2 to balance and labeled with either 3H-thymidine or 3H-proline and 35S-sulfate. Cell proliferation was significantly inhibited by hypoxia in synovium but not in tendon (P = 0.03). In parallel, the synthesis of non-collagenous proteins was significantly reduced in synovium but not in tendon (P = 0.006). In both tissues hypoxia significantly inhibited collagen synthesis. On the other hand, hypoxia had no significant effect on the synthesis of new proteoglycans as determined by 35S-sulfate incorporation. Hypoxia can inhibit cell proliferation and alter synthesis of matrix components in synovial tissue, but may only have minor effects on non-collagen protein synthesis in tendon explants from the carpal canal of rabbit forepaws.

A gated trapping strategy with a two-time constant and a delay for catching in-field generated ions that range over three decades in mass-to-charge and two decades in velocity in Fourier-transform mass spectrometry.

In-field, matrix-assisted laser desorption/ionization (MALDI) may provide a means to keep part of the original promise of Fourier-transform mass spectrometry (FTMS) to give high performance and versatile mass spectrometry from a mechanically simple instrument. Gated trapping has been employed as a means of catching MALDI-produced ions in the FTMS trap. This approach is important for both in-field and externally produced ions. Even with improvements, gated trapping has not yet been able to catch ions over wide ranges of mass-to-charge and velocity. A design of a "two-time constant with a delay" gated trapping strategy using "idealized" potentials in a normalized system is given as an example to establish that in principle gated trapping strategies can capture ions that range over three decades of m/z and two decades in velocity. A procedure for calculating a physical system from the normalized system is given. The design is tolerant of variations in the physical parameters used to define the physical system from the normalized system.

A method for quantification from composite spectra: application to the determination of isomeric DNA photoproducts by tandem mass spectrometry.

Quantification of mixture components from their composite optical or mass spectra is a common need in analytical chemistry. We encountered the need when applying a combination of enzymatic digestion with nuclease P1 and tandem mass spectrometry to a mixture of isomeric photomodified oligodeoxynucleotides. In the procedure, we collisionally activated the [M - H]- or [M + Na - 2H]- ion of trinucleotide triphosphates, which were extricated enzymatically from the larger, damaged oligodeoxynucleotides, and we measured the relative abundances of characteristic fragment ions. The results sometimes yield curved calibrations for plots of the relative fragment ion abundances in the product ion spectra of isomers versus their relative amounts. We developed a normalized linear model, which brings understanding to the nonlinear plots and allows quantification of the mixture components from their composite spectra. The outcome demonstrates a general quantification procedure and shows that different yields for generating fragment ions from different constituents of the mixture cause the curved calibration lines.

Measuring and characterizing force exposures during computer mouse use.

OBJECTIVES: The purpose of this study was to develop and validate a sampling strategy for characterizing the finger force exposures associated with computer mouse use. METHODS: Mouse forces were measured from 16 subjects (8 men, 8 women), on 3 separate days, at their actual workstations while they performed (i) their regular work, (ii) a battery of standardized tasks, and (iii) simulated mouse use. RESULTS: The forces applied to the mouse did not vary between hours or days. During regular work, the mouse was used 78.0 (SD 40.7) times per hour, accounting for 23.7 (SD 9.5)% of the worktime. The mean forces applied to the sides and button of the mouse were low, averaging 0.6 % (0.35 N) and 0.8 % (0.43 N) of the maximal voluntary contraction, respectively. The forces applied to the mouse during the standardized tasks differed from the regular work forces; however, there were moderate-to-strong correlations between the 2 measures. CONCLUSIONS: With respect to performing exposure assessment studies, the 3 major findings were (i) mouse force measurements should be made while subjects perform their actual work in order to characterize the absolute applied force accurately, (ii) the forces applied to the mouse during the performance of a short battery of standardized tasks can be used to characterize relative exposure and identify computer operators or work situations for which higher forces are applied to the mouse, and (iii) subjects cannot accurately simulate mouse forces.

Classification criteria and severity assessment in work-associated upper extremity disorders: methods matter.

Work-associated musculoskeletal disorders of the upper extremity are common and disabling. Research on these disorders is needed and requires valid methods of classification of the disorders for epidemiologic studies and measurement of their impact on functional status. This commentary discusses the methodologic aspects of classification and functional status assessment in upper extremity musculoskeletal disorders.

Sensitivity of trapezius electromyography to differences between work tasks - influence of gap definition and normalisation methods.

Surface electromyography (EMG) has been used extensively to estimate muscular load in studies of work related musculoskeletal disorders, especially for the trapezius muscle. The occurrences of periods of EMG silence (gaps), the time below a predetermined threshold level (muscular rest) and various percentiles of the amplitude distribution (APDF) are commonly used summary measures. However, the effects of the criteria used to calculate these measures (e.g., gap duration, threshold level, normalisation method) on the sensitivity of these measures to accurately differentiate work loads is not well known. Bilateral trapezius EMG was recorded, for a full workday, for 58 subjects following both maximal (MVE) and submaximal (RVE) reference contractions. Gap frequency, muscular rest, and percentiles were derived for eight fundamental work tasks. The calculations were performed using different gap duration criteria, threshold levels and normalisation methods.A gap duration of less than 1/2 s, and threshold level approximately 0.3% MVE for gap frequency, and approximately 0.5% MVE for muscular rest, were the criteria that optimised sensitivity to task differences. Minimal sensitivity to tasks and a high sensitivity to individuals was obtained using gap frequency with a threshold level of approximately 1% MVE. Normalisation to RVE, rather than MVE, improved sensitivity to differences between tasks, and reduced undesirable variability. Muscular rest was more sensitive to task differences than APDF percentiles.