Improving the Classical Geophone Sensor Element by Digital Correction

Geophones are highly sensitive motion transducers that have been used by seismologists and geophysicists for decades. The conventional geophone's ratio of cost to performance, including noise, linearity and dynamic range is unmatched by advanced modern accelerometers. However, the problem of this sensor is that it measures velocity, and that the linear frequency range is limited to frequencies above the natural frequency, typically at 4-12 Hz. It is shown in this paper how the sensor signal can be digitally linearized 2 decades below the natural frequency obtaining a sensor that allows the user to measure displacement, velocity or acceleration with high sensitivity and large dynamic range

Effects of consecutive workdays and days off on low back pain, fatigue and stress:Prospective cohort study among warehouse and construction workers

Objectives Limited knowledge exists about day-to-day changes in physical and mental symptoms in warehouse and construction workers. This study investigated the associations between consecutive workdays and days off with low back pain (LBP) intensity, bodily fatigue and mental stress. Methods Participants (n=224) received daily questions for 21 days about LBP, fatigue, stress (outcome, 0-10 scales), and workdays and days off (exposure). We tested associations between 1-3 workdays (n=148) and 1-2 days off (n=158) with LBP intensity, bodily fatigue and mental stress after work and the following morning using linear mixed models with repeated measures controlling for relevant confounders. Results Consecutive workdays led to progressively increased LBP intensity, with three workdays increasing LBP intensity by 1.76 (95% CI 1.48 to 2.03) points. Bodily fatigue and mental stress increased after one workday (2.06 (95% CI 1.80 to 2.32) and 0.97 (95% CI 0.77 to 1.17) points, respectively) and remained stable for three workdays. After 1 day off, bodily fatigue and mental stress decreased -1.82 (95% CI -2.03 to -1.61) and -0.88 (95% CI -1.05 to -0.71) points, respectively, without decreasing further. In contrast, LBP intensity decreased progressively -1.09 (95% CI -1.27 to -0.91) and -1.45 (95% CI -1.67 to -1.24) points after 1 and 2 days off, respectively. Conclusions Workdays and days off affected the outcome variables differently. LBP intensity progressively increased with consecutive workdays, while workers needed 2 days off to recover. This study provides valuable knowledge about how to organise the workweek to prevent LBP, fatigue and stress, potentially reducing labour market withdrawal.</p

Strength training to contraction failure increases voluntary activation of the quadriceps muscle shortly after total knee arthroplasty:a cross-sectional study

OBJECTIVE: The objective of this study was to investigate voluntary activation of the quadriceps muscle during one set of knee extensions performed until contraction failure in patients shortly after total knee arthroplasty. DESIGN: This was a cross-sectional study of 24 patients with total knee arthroplasty. One set of knee extensions was performed until contraction failure, using a predetermined 10 repetition maximum loading. In the operated leg, electromyographic (EMG) activity of the lateral and medial vastus, semitendinosus, and biceps femoris muscles was recorded during the set. Muscle activity (%EMGmax) and median power frequency of the EMG power spectrum were calculated for each repetition decile (10%–100% contraction failure). RESULTS: Muscle activity increased significantly over contractions from a mean of 90.0 and 93.6 %EMGmax (lateral vastus and medial vastus, respectively) at 10% contraction failure to 99.3 and 105.5 %EMGmax at 100% contraction failure (P = 0.009 and 0.004). Median power frequency decreased significantly over contractions from a mean of 66.8 and 64.2 Hz (lateral vastus and medial vastus, respectively) at 10% contraction failure to 59.9 and 60.1 Hz at 100% contraction failure (P = 0.0006 and 0.0187). CONCLUSION: In patients shortly after total knee arthroplasty, 10 repetition maximum–loaded knee extensions performed in one set until contraction failure increases voluntary activation of the quadriceps muscle during the set. CLINICAL TRIALS: Gov-identifier: NCT01713140 to the abstract to increase trial transparency

Glial nuclear aggregates of superoxide dismutase-1 are regularly present in patients with amyotrophic lateral sclerosis

The most common cause of amyotrophic lateral sclerosis (ALS) is mutations in superoxide dismutase-1 (SOD1). Since there is evidence for the involvement of non-neuronal cells in ALS, we searched for signs of SOD1 abnormalities focusing on glia. Spinal cords from nine ALS patients carrying SOD1 mutations, 51 patients with sporadic or familial ALS who lacked such mutations, and 46 controls were examined by immunohistochemistry. A set of anti-peptide antibodies with specificity for misfolded SOD1 species was used. Misfolded SOD1 in the form of granular aggregates was regularly detected in the nuclei of ventral horn astrocytes, microglia, and oligodendrocytes in ALS patients carrying or lacking SOD1 mutations. There was negligible staining in neurodegenerative and non-neurological controls. Misfolded SOD1 appeared occasionally also in nuclei of motoneurons of ALS patients. The results suggest that misfolded SOD1 present in glial and motoneuron nuclei may generally be involved in ALS pathogenesis

Squeezed vacuum states from a whispering gallery mode resonator

Squeezed vacuum states enable optical measurements below the quantum limit and hence are a valuable resource for applications in quantum metrology and also quantum communication. However, most available sources require high pump powers in the milliwatt range and large setups, which hinders real world applications. Furthermore, degenerate operation of such systems presents a challenge. Here, we use a compact crystalline whispering gallery mode resonator made of lithium niobate as a degenerate parametric oscillator. We demonstrate about 1.4 dB noise reduction below the shot noise level for only 300 $\mu\text{W}$ of pump power in degenerate single mode operation. Furthermore, we report a record pump threshold as low as 1.35 $\mu\text{W}$. Our results show that the whispering gallery based approach presents a promising platform for a compact and efficient source for nonclassical light.Comment: $\copyright$ 2019 Optical Society of America. Users may use, reuse, and build upon the article, or use the article for text or data mining, so long as such uses are for non-commercial purposes and appropriate attribution is maintained. All other rights are reserve