Automatic testing device facilitates noise checks and electronic calibrations

Automatic Digital Noise Checker determines the noise content of the many analog imputs of a data acquisition system and whether the Electronic Calibrations /EC/ on some data channels are operating properly

Optovibrometry: tracking changes in the surface tension and viscosity of multicomponent droplets in real-time

An instrument was developed for measuring real time changes in the surface tension and viscosity of multicomponent droplets of miscible liquids and other soft materials. Droplets containing glycerol and water were supported on superamphiphobic surfaces and vibrated by applying a short mechanical impulse. Laser light was refracted through the droplets and allowed to fall on the surface of a photodiode. Time dependent variations in the intensity measured by the photodiode during vibration were used to monitor the decay of the droplet oscillations. The frequencies and spectral widths of the droplet vibrational resonances were then obtained from Fourier transforms of these time dependent intensity signals. A recently developed model of viscoelastic droplet vibration was used along with these values and measurements of the drop dimensions to extract the surface tension and viscosity of the drops as they evaporated. Collection of data was automated and values of frequency, spectral width, drop size, surface tension and viscosity were obtained with a time resolution of three seconds over a period of thirty minutes. The values of surface tension and viscosity obtained were shown to be in good agreement with literature values obtained from bulk glycerol/water solutions; thus validating the technique for wider application to other multicomponent liquids and soft matter systems

Single droplet microrheology

The vibration of microlitre sized drops in partial contact with a substrate was used to extract the rheological properties of multicomponent fluids. Sessile and pendant drop vibration was triggered using a short mechanical impulse. Sessile drops were supported on superhydrophobic surfaces and their vibration monitored using laser light, refracted through the drops and focussed on the sensor of a photodiode. Pendant drops were suspended from clean pipette tips and their vibration was recorded using a high speed camera. Time dependent photodiode intensity/centre of mass variations were Fourier transformed to extract the frequency and spectral widths of vibration. The vibration of aqueous glycerol sessile drops was tracked in real time as the drops evaporated. The changing surface tension and viscosity were extracted using a simple model describing the vibration of a viscous sessile drop. The values of surface tension and viscosity obtained for initial bulk solutions were shown to be in good agreement with literature values, however evaporating drops showed signs of surface contamination after ∼300s. The vibration of sessile drops of aqueous poly(acrylamide-co-acrylic acid) solutions was used to calculate the shear storage and loss moduli using a simple theoretical model. The resulting rheological properties were found to be in agreement with microrheology measurements of the same solutions. The model was also applied to pendant drops of aqueous poly(acrylamide-co-acrylic acid). The majority of the rheological data measured for the pendant drops agreed with microrheology and sessile drop data. Drop vibration therefore provides an accurate method of quantifying the rheological properties of single drops in short time

Clinical review: Early patient mobilization in the ICU

Early mobilization (EM) of ICU patients is a physiologically logical intervention to attenuate critical illness-associated muscle weakness. However, its long-term value remains controversial. We performed a detailed analytical review of the literature using multiple relevant key terms in order to provide a comprehensive assessment of current knowledge on EM in critically ill patients. We found that the term EM remains undefined and encompasses a range of heterogeneous interventions that have been used alone or in combination. Nonetheless, several studies suggest that different forms of EM may be both safe and feasible in ICU patients, including those receiving mechanical ventilation. Unfortunately, these studies of EM are mostly single center in design, have limited external validity and have highly variable control treatments. In addition, new technology to facilitate EM such as cycle ergometry, transcutaneous electrical muscle stimulation and video therapy are increasingly being used to achieve such EM despite limited evidence of efficacy. We conclude that although preliminary low-level evidence suggests that EM in the ICU is safe, feasible and may yield clinical benefits, EM is also labor-intensive and requires appropriate staffing models and equipment. More research is thus required to identify current standard practice, optimal EM techniques and appropriate outcome measures before EM can be introduced into the routine care of critically ill patients

Single droplet microrheology

The vibration of microlitre sized drops in partial contact with a substrate was used to extract the rheological properties of multicomponent fluids. Sessile and pendant drop vibration was triggered using a short mechanical impulse. Sessile drops were supported on superhydrophobic surfaces and their vibration monitored using laser light, refracted through the drops and focussed on the sensor of a photodiode. Pendant drops were suspended from clean pipette tips and their vibration was recorded using a high speed camera. Time dependent photodiode intensity/centre of mass variations were Fourier transformed to extract the frequency and spectral widths of vibration. The vibration of aqueous glycerol sessile drops was tracked in real time as the drops evaporated. The changing surface tension and viscosity were extracted using a simple model describing the vibration of a viscous sessile drop. The values of surface tension and viscosity obtained for initial bulk solutions were shown to be in good agreement with literature values, however evaporating drops showed signs of surface contamination after ∼300s. The vibration of sessile drops of aqueous poly(acrylamide-co-acrylic acid) solutions was used to calculate the shear storage and loss moduli using a simple theoretical model. The resulting rheological properties were found to be in agreement with microrheology measurements of the same solutions. The model was also applied to pendant drops of aqueous poly(acrylamide-co-acrylic acid). The majority of the rheological data measured for the pendant drops agreed with microrheology and sessile drop data. Drop vibration therefore provides an accurate method of quantifying the rheological properties of single drops in short time

Social Support and Total Joint Replacement: Differences Preoperatively between Patients Living Alone and Those Living with Others

Introduction: Social relationships affect mental health, physical health, and mortality risk. Little is known about social support and patients electing to have total joint replacement (TJR) surgery. We explored the differences between participants living alone and those living with at least one other adult prior to TJR surgery. Materials & methods: Preoperative and 6 month postoperative FORCE-TJR Registry survey data were collected from 6269 primary unilateral TJR patients between May 2011 and December 2013. Data included demographics, comorbid conditions, operative joint pain severity (HOOS/KOOS), musculoskeletal disease burden, physical function (SF-36 PCS), and mental health (SF36 MCS). Results: Participants living alone were more likely to be older, female, on Medicare, with a high school education or less, and a racial/ethnic minority. Prior to surgery, they reported a greater number of comorbid conditions and non-surgical joints causing pain. Those living alone also had lower mean MCS summary measure, lower Social Functioning Scale score and a lower HOOS/KOOS Activities of Daily Living score before TJR. There were no differences preoperatively in mean BMI, mean PCS, or HOOS/KOOS surgical joint pain, symptoms, or quality of life scores between the two groups. Six months postoperatively, those living alone had lower mean PCS and MCS, but were more likely to report less pain and symptoms in the surgical joint. Unadjusted analyses of mean change over time found less improvement in PCS for those living alone compared to those not living alone. Conclusion: Recognizing differences in social support prior to TJR surgery could inform interventions and potentially influence patient reported outcomes postoperatively

Level of Pain and Disability at Time of TKR across the Past 10 Years: Results from Two National Cohorts

Introduction: A recent analysis reported a growing numbers of younger US adults with knee pain consistent with osteoarthritis (OA), although parallel analyses of knee x-rays found no increase in the classic radiographic signs of OA. The accompanying editorial evoked the need to understand if surgeons are performing surgery at an earlier stage in the condition.1 We compared pre-operative demographic and symptom profiles of a national US cohort of OA patients undergoing primary total knee replacement (TKR) in 2011-2012 with a national US cohort of patients from 2000-2004 to evaluate change, if any, in the timing of surgery as measured by patient pain and function. Methods: Following informed consent, the 2011-2012 national research study collected comprehensive data including demographic, comorbidity, and patient-reported pain and physical function, from a national sample of TKR patients. Comparable data from a national sample collected by one implant manufacturer between 2000-2004 were analyzed. Descriptive statistics compared the demographic and symptom profiles of the two cohorts. Results: There were fewer females in the 2011-2012 cohort (n=2363) compared to the 2000-2004 cohort (n=7144) (61.62%, vs. 66.72%). The 2011-2012 cohort was younger than the 2000-2004 cohort (66.7 years, vs. 68.12 years) and had a lower mean BMI (31.5 vs 32.3). Pre-operative physical function scores (SF36/PCS) were 3 points higher in 2011-2012 than 2000-2004 (33.2 vs. 30.41). When compared to the national PCS norm of 50 (SD=10), TKR patients from both time periods reported pre-operative function levels almost 2 standard deviations below the national norm. There was no significant difference in terms of emotional health (SF36/MCS scores: 51.85 for the 2011-2012 cohort vs. 51.83 for the 2000-2004 cohort). Conclusion: Despite the significant growth in the use of primary TKR in the last decade, especially among younger patients, TKR patients continue to report significant disability at the time of surgery

Differential Burden of Musculoskeletal Pain in Blacks and Whites at the Time of Total Joint Replacement Surgery

Introduction: The existence of racial disparities in total knee (TKR) and hip (THR) replacement outcomes is well established. The role of musculoskeletal co-morbidities among black and white TKR patients at the time of surgery were investigated in a prospective cohort enrolled in the FORCE-TJR consortium of 131 surgeons in 22 US states. Materials & methods: Descriptive analyses were performed on 3,306 TKR and 2,439 THR patients. Data included sociodemographic factors (age, sex, race), BMI, comorbid conditions using the modified Charlson comorbidity scores, burden of musculoskeletal disease using the Knee/Hip injury and Osteoarthritis Outcome Score (KOOS/HOOS) in both knees and hips, emotional health based on the Short Form 36 (SF-36) Mental Component Score (MCS) and physical function based on the Physical Component Score (SF-36 PCS). Factors associated with pre-operative surgical joint pain and function were examined using multivariate stepwise linear regression models. Results: Compared to Whites, Blacks (143 hips and 201 knees) reported worse surgical joint pain (mean pain: 39.3 vs. 49.2 (hip); 43.4 vs. 53.2 (knee)), poorer surgical joint function (mean function: 38.9 vs. 45.7 (hip); 45.9 vs. 53.4 (knee)), poorer global function (mean PCS: 30.0 vs. 31.6 (hip); 31.3 vs. 33.1 (knee)), and more non-operative joints pain. (All p\u3c0.03). In adjusted multivariable models, differences at the time of surgery in surgical joint symptoms and global function were explained by differences in musculoskeletal pain in the hips, knees, and low back. Conclusion: Greater burden of musculoskeletal pain explains differences in pre-operative pain and function between Blacks and Whites and likely impacts rehabilitation and subsequent TJR outcomes