Mean Contact Time Research Articles

Reliability and Validity of Temporal Parameters during the Side Hop Test in Patients after Anterior Cruciate Ligament Reconstruction.

Background: The side hop test (SHT) measures the number of jumps performed over 30 s. Although this measure has demonstrated its value in clinical practice, the temporal parameters of the SHT allow for a deeper analysis of the execution strategy. The aim of this study is to assess the reliability and construct validity of contact time parameters during the SHT recorded by a video analysis system in anterior cruciate ligament reconstructed (ACLR) patients. Methods: We investigated the reliability (intra-rater, standard error of measurement (SEM), and minimum detectable change (MDC)), discriminant validity (operated (OP) versus non-operated (NOP) side), and convergent validity (relationship with strength and psychological readiness) of SHT contact time parameters, number of valid hops and limb symmetry index (LSI) in 38 ACLR patients. Contact time parameters are presented as mean, standard deviation (SD), and coefficient of variation (CV) of contact time. Results: Intra-tester reliability was good to excellent for all contact time parameters. For discriminant validity, the mean and SD contact times of the OP leg were significantly longer than those of the NOP leg, although the difference was smaller than the SEM and MDC values. The number of valid jumps and CV contact time parameters were not significantly different. Isokinetic quadriceps strength (60°/s) was strongly correlated with mean contact time for both legs. However, psychological readiness was not correlated with any of the contact time parameters. Conclusions: Temporal parameters of the SHT measured on video analysis are valid and reliable parameters to assess the performance strategy of the SHT. The results should be interpreted with caution regarding the SEM and MDC values. Further studies are needed to measure criterion validity, inter-rater reliability, and responsiveness.

Asymmetric gap balancing improves knee kinematic following primary total knee arthroplasty

PurposeThe purpose of this study was to demonstrate closer-to-normal knee kinematics following primary total knee arthroplasty (TKA) performed establishing asymmetric gap balancing intraoperatively.Material and methodTwo age-, sex-, BMI-matched groups of patients underwent medially stabilized TKA because of isolated knee disease. Group A (12 patients) underwent “unrestricted” kinematic alignment (uKA) according to Howell while group B (15 patients) received robot-assisted “simplified” KA (sKA) with an alignment goal (Hip-Knee-Ankle axis-HKA) ± 5° respect to the mechanical axis. Intraoperatively, in group B, the flexion gap at 90° was first set at an average of 1.5 mm (0–5 mm; SD 4.4 mm) tighter in the medial compartment with respect to the lateral; in the same way, the extension gap was then set at an average of 2.0 mm (0–4.5 mm; SD 3.1 mm) tighter in the medial compartment with respect to the lateral. All patients, including a non-arthritic cohort (group C: 5 controls) underwent gait analysis using an instrumented treadmill (WalkerView–WV) equipped with an instrumented belt armed with a 3D video camera. The WV software evaluated multiple spatiotemporal and kinematic parameters, including: (1) contact time (s); (2) knee ROM during gait cycle; (3) step length percentage with respect to total gait (%) and pure step length (cm). Statistical analyses included t-Test and ANOVA and were conducted by using SPSS.ResultsAt the final FU, significant differences were noted during gait between the two TKA groups (uKA-sKA) and the controls. Both TKA groups showed superior mean contact time on the surgical knee (uKA 1 s; sKA 0.97 s) as compared to the controls (0.72 s) (P = 0.002) while no differences were found between them (P = 0.11). TKA groups showed a lower, maximum ROM in the surgical knee (mean uKA 36º; mean sKA 49º) relative to the controls (mean 57º) (P < 0.05) but a statistical difference was found between them (P = 0.003). Both TKA groups showed a higher step length percentage with respect to the total gait and a shorter step length on the surgical side (uKA: mean 8.28% and mean step length 35.5 cm; sKA: mean 8.38% and mean step length 34.6 cm) in comparison to the controls (mean 3.38%; mean step length 71.4 cm) (P < 0.05) while no statistical differences were found between them.ConclusionTo our knowledge, this was the first study to exhibit the kinematic advantages of a slightly asymmetric gap balancing during KA TKA. Combining a medially-stabilized implant design and a surgical technique aiming to obtain a tighter medial compartment represents a promising approach to improve outcomes after TKA.Graphical

Ameboid cell migration through regular arrays of micropillars under confinement

Migrating cells often encounter a wide variety of topographic features—including the presence of obstacles—when navigating through crowded biological environments. Unraveling the impact of topography and crowding on the dynamics of cells is key to better understand many essential physiological processes such as the immune response. We study the impact of geometrical cues on ameboid migration of HL-60 cells differentiated into neutrophils. A microfluidic device is designed to track the cells in confining geometries between two parallel plates with distance h, in which identical micropillars are arranged in regular pillar forests with pillar spacing e. We observe that the cells are temporarily captured near pillars, with a mean contact time that is independent of h and e. By decreasing the vertical confinement h, we find that the cell velocity is not affected, while the persistence reduces; thus, cells are able to preserve their velocity when highly squeezed but lose the ability to control their direction of motion. At a given h, we show that by decreasing the pillar spacing e in the weak lateral confinement regime, the mean escape time of cells from effective local traps between neighboring pillars grows. This effect, together with the increase of cell-pillar contact frequency, leads to the reduction of diffusion constant D. By disentangling the contributions of these two effects on D in numerical simulations, we verify that the impact of cell-pillar contacts on cell diffusivity is more pronounced at smaller pillar spacing.

Antibiotic Emulgel: Design and Characterization for Topical Drug Delivery

Objectives: The benefits of topical drug delivery systems, which have been used for centuries, include the ability to deliver medications both quickly to the affected area where they are most effective and over an extended period of time. These systems lengthen the drug's mean resident time and contact time. The design and characterization of an antibiotic emulgel for topical medication administration is a goal of the current investigation. Methods: Cefpodoxime Proxetil emulgel were prepared using different concentration of Carbopol 934, HPMC K4M and xanthan gum as gelling agents and evaluated the relevant parameters such as physical examinations, pH, extrudability, spreadability, viscosity, swelling index, drug content, in-vitro diffusion studies and microbiology activities. Results: All formulations are neutral and viscosity of emulgel was found in the acceptable limits. On physical evaluations were found to be optimum in terms spreadability, swelling index and extrudability. Drug content of all formulations were found in the ranges 69.73% to 97.58% and CEF4 emulgel exhibiting the highest drug concentration and the lowest percentage drug release due to its controlled release pattern and proven non-fickian diffusion mechanism release. The results found that, the selected formulations proven better bacterial activities against both gram positive and gram negative organisms. Conclusions: Type and concentration of polymers can have an impact on the drug permeability studies and physical-chemical characteristics of the developed antibiotic emulgel, which had excellent results and was suitable for possible therapeutic purposes.

Maximization of LEO Nanosatellite's Transmission Capacity to Multiple Ground Stations: Orbit Selection and Requirements on Attitude Control

This article presents the study of an optimized orbital configuration for a three-axis stabilized 6U LEO nanosatellite that accommodates a polarized calibrator designed to transmit a calibrated signal to seven ground telescopes devoted to cosmic microwave background detection with an accepted maximum absolute pointing error of 4 arcmin; visibility windows and revisit time are maximized by orbit selection and active attitude control considering no possibility of orbital mobility. The solution approach is divided into two parts: in the first part, a dedicated sensitivity study is conducted to find the optimal orbital parameters that maximize the mean contact time between the spacecraft and the list of ground telescopes; in the second part the identified promising orbital configurations are propagated to evaluate the attitude change maneuvers needed during the passage above each telescope to guarantee continuous signal transmission. The results of the sensitivity study report the maximum values for the duration and frequency of the CubeSat-to-Ground station visibility periods. The required performance in terms of pointing accuracy and repointing velocity is later used to propose an attitude control loop for precision pointing and to define a commercial off the shelf Attitude Determination and Control System architecture.

The Podoprint® plantar pressure platform: Evaluation of reliability and repeatability, and determination of the normality parameters

IntroductionThe Podoprint® pressure platform system is widely used in routine podiatric clinical practice to measure plantar pressures. It allows non-invasive examination of the patient, and provides fast results with high levels of precision, reliability, and repeatability. Once these conditions have been demonstrated, the clinical and/or research use of baropodometry allows results to be obtained in the field of podology that are far from inconsiderable.The study was designed to evaluate the repeatability and reliability of the platform, and to identify the normal foot pressure parameters. MethodsRecords were collected from 52 random healthy individuals, 10 men and 42 women, in two sessions separated by one week. The study variables were: maximum pressure, mean pressure, support surface areas (heel, midfoot, and forefoot), and contact time. Repeatability and reliability were evaluated by calculating the interclass correlation coefficient (ICC) and the coefficient of variation (CV) in the three tests. ResultsThe ICCs showed moderate to good repeatability for the variables of interest, and the CVs were all less than 18%. The maximum pressure was under the forefoot (mean 2675.4 ± 513.8 g/cm2). The mean contact time of the steps was 0.72 ± 0.07 s. ConclusionsThe Podoprint® system is a reliable tool for evaluating the distribution of plantar pressures in the dynamic study of the barefoot gait of healthy individuals.

General Practitioner Time Availability Per Inhabitant Per Year: A New Indicator to Measure Access to Primary Care.

The number of general practitioners (GPs) per inhabitant, used commonly as an indicator of primary care (PC) access, reports only imprecisely on the true availability of GPs. The aim of this study is to develop a new PC access indicator that better reflects the availability of GPs to take care of patients at the population level, the average GP time availability per inhabitant per year. We extracted the data from the Commonwealth Fund International Health Policy Survey of Primary Care Physicians conducted in 2015, including 11 Western countries and 12,049 randomly drawn GPs. We built the indicator by combining two questions about weekly workload in hours and percentage of time spent on face-to-face contact with patients. The indicator was then adjusted regarding the number of GPs, the weeks worked per year and the country's population size. On average, GPs worked 43 h a week. The average time spent on face-to-face contact with patients was 30.5 h/week (35 h including emails and telephone contact), ranging from 22 h in Sweden and 38 h in France. The mean time available of GPs for face-to-face contact was 69 min/inhabitant/year, ranging from 38 min in Sweden to 118 min in Australia. Including email and telephone contact, the mean contact time rose to 79 min/inhabitant/year, ranging from 48 min in Sweden to 127 min in Australia. The new indicator provides an accurate and sensitive estimate of a GP's true time availability at the population level. Results should be interpreted in the context of PC workforce organization, which may help guide GP workforce development.

Tertiary lymphoid organs in renal chronic allograft rejection

Abstract Chronic allograft rejection remains a major obstacle to long-term allograft survival. The immunologic role of tertiary lymphoid organs (TLO) in allograft rejection is unclear. Here, we employed a chronic renal allograft rejection model in mice and intravital 2-photon microscopy to investigate the function of TLO in transplant rejection. CB6F1 (F1) RIP-LTα (preformed TLO) or F1 (no TLO) kidney grafts were transplanted to WT B6 recipients and survival monitored. To investigate immunologic function of TLO, we adoptively transferred B6-RIPLTα CD11c-YFP mice with 10m naïve dsRed OT-I T cells or 10m CTR-labeled NP-specific B cells + 10m CFP+ OT-II cells and immunized with NP-OVA + alum. Intravital 2P imaging of renal TLO was performed at time points 0, 3, 6, 24 or 72 hours after immunization. 4D image analysis was performed and mean speed, displacement, arrest coefficient (AC) and contact times (CT) with DC were calculated for OT-I, OT-II and NP-B cells. F1 RIP-LTα grafts rejected significantly faster (MST= 54) than F1 grafts (MST= 225), demonstrating that TLO contribute to allograft rejection. F1 RIP-LTα grafts contained similar numbers of, but larger TLO than F1 grafts as demonstrated by histology. Mean speed and displacement of OT-I and OT-II cells significantly decreased over time after immunization while AC and mean CT significantly increased. B cell mean speed, displacement and AC increased after immunization. These data are consistent with B cell activation and productive T cell-DC interactions and mirror previously reported data in secondary lymphoid organs. We provide first evidence that TLO provide a local structure for T and B cell activation that propagates anti-graft immune responses in the setting of chronic rejection.

P1896Single-procedure success-rate of pulmonary vein isolation using point-by-point tagging lesions algorithm based on contact force technology: preliminary results of the multicentric SMOP study

Abstract Background Pulmonary veins isolation (PVI)is an effective therapy for atrial fibrillation (AF), recommended by current guidelines. However, recurrences after first radio-frequency (RF) catheter ablation (CA) are still high. PV reconnection could be due to ineffective transmural lesions; automated ablation lesion tags (the VisiTag algorithm) based on predefined parameters of catheter stability and contact force (CF) have been developed to allow the detection of ineffective ablation lesion, nevertheless there is a lack of multicenter studies exploring this technology. Objective the aim of our study was to assess the rate of recurrence after a first PVI procedure in a large, multicentric Italian population and to explore the efficacy of Visitag algorithm (CARTO 3) used to guide RF ablation of AF. Methods we analyzed 214 patients of the SMOP-AF study (Substrate Mapping as Outcome Predictor in Atrial Fibrillation Ablation), a prospective multi-centric study enrolling patients with paroxysmal and persistent AF undergoing a first PVI procedure after an high-density mapping during sinus rhythm. During the procedure, ablation was guided by an automated annotation system in which tag based on predefined parameters were displayed real-time in each lesion site on the electroanatomical map. Visitag settings for the catheter position stability were a 2,5 mm distance limit for at least 7 sec and a minimum CF of 5 g over 30% of the ablation and a FTI&gt;400 g*s. Where available (n=106, 49.5%), Ablation Index (AI), which also incorporates information on delivered RF power, was used instead of FTI to guide RF ablation with a threshold range of 400–550 for anterior/roof and 330–420 for posterior/inferior segments. Minimum and mean contact force, time and power values for each RF-lesion were recorded while both FTI and AI values were calculated automatically by the CARTO system. Comparison between groups were made by cross-tables, Mann-Whitney or Student T test as appropriated. Results the mean age of the enrolled population was 59±9 years, left ventricular ejection fraction was 59±9%. AF was paroxysmal in 89.7%, persistent in 10.3% of the patients and refractory to at least one anti-arrhythmic drug in 86.4% of the population. At 3 months follow-up 85% of the patients were free from AF recurrences and the success rate increased to 90.8% at 3–6 months, and 86.3% at 3–12 months follow-up. The mean ablation time was shorter in AI-guided vs. FTI-guided procedures (31±9 vs 46±29 min; p&lt;0.001). There was a trend toward a reduction in AF recurrences when AI vs. FTI was used, both at 6 and 12 months (respectively 5,4% vs 13.6%; p 0.06 and 9.6% vs 18.5%; p 0.08). Conclusion PVI isolation using dedicated algorithms developed to guide the effectiveness of RFCA leads to a very high success-rate after a single procedure. The use of AI, which integrates contact force information with delivered power, reduces the procedural time and increases the overall success-rate

Start-up propulsion biomechanics changes with fatiguing activity in persons with spinal cord injury

Objective: Shoulder pathology is a common condition in wheelchair users that can considerably impact quality of life. Shoulder muscles are prone to fatigue, but it is unclear how fatigue affects start-up propulsion biomechanics. This study determines acute changes in start-up wheelchair propulsion biomechanics at the end of a fatiguing propulsion protocol. Design: Quasi-experimental one-group pretest-postest design. Setting: Biomechanics laboratory. Participants: Twenty-six wheelchair users with spinal cord injury (age: 35.5 ± 9.8 years, sex: 73% males and 73% with a paraplegia). Interventions: Protocol of 15 min including maximum voluntary propulsion, right- and left turns, full stops, start-up propulsion, and rests. Outcome measures: Maximum resultant force, maximum rate of rise of applied force, mean velocity, mean fraction of effective force, and mean contact time at the beginning and end of the protocol during start-up propulsion. Results: There was a significant reduction in maximum resultant force (P < 0.001) and mean velocity (P < 0.001) at the end of the protocol. Also, contact time was reduced in the first stroke of start-up propulsion (P < 0.001). Finally, propelling with a shorter contact time was associated with a greater reduction in performance (maximum velocity) at the end of the protocol. Conclusion: There are clear changes in overground propulsion biomechanics at the end of a fatiguing propulsion protocol. While reduced forces could protect the shoulder, these reduced forces come with shorter contact times and lower velocity. Investigating changes in start-up propulsion biomechanics with fatigue could provide insight into injury risk.

Being mindful of mindfulness interventions in cancer: A systematic review of intervention reporting and study methodology.

While mindfulness-based stress reduction (MBSR) and mindfulness-based cognitive therapy (MBCT) have demonstrated efficacy in clinical populations, the potential therapeutic benefit of mindfulness in the context of cancer is less clear. The aim of this review was to critically appraise mindfulness intervention reporting and study methodology. Studies using randomized control trial design and/or a control arm were included. PubMed, Medline, PsycINFO, CINAHL, and Embase databases between January 1999 and April 2017 were searched. Studies were assessed on (1) reported theoretical framework, (2) intervention description, and (3) justification of modifications to standardized MBSR/MBCT. The overall quality of study design and research methodology were also assessed. Of 30 studies identified, none adhered to MBSR. Modified versions of MBSR were reported in 19 studies. Five studies reported variants of MBCT, 1 used a combination of MBSR/MBCT, and 5 inadequately documented the intervention/ theoretical framework. Overall, component and timeline modifications were poorly documented and justified. Mean intervention contact time was less than standardized MBSR/MBCT protocols. Target outcomes were poorly justified, and 12 studies failed to identify a primary aim, reporting multiple outcomes. Only 9 of 15 studies recruiting clinical populations included clinical cutoffs, and an active therapeutic control was included in 4 studies. Mindfulness is increasingly considered a standard therapy in psycho-oncology. While many studies proclaim benefits, considerable variability, modification to standardized protocols, and claims of benefit often reflect decreases in sub-clinical supportive care symptomology rather than therapeutic relief of clinically significant psychological disorders.

Effects of a trail mountain race on neuromuscular performance and hydration status in trained runners.

The aims of this study were to examine the effects of a trail mountain race (TMR) on hydration status and neuromuscular performance of recreational trail runners, and to determine the relationship among these parameters, subject's characteristics and competitive performance. Thirty-five male recreational trail runners (age 38.1±9.5 years; height 177.3±5.8 cm; body mass 73.8±8.4 kg) were assessed before and after a 21.1-km TMR. Hydration status (urine color [Ucol] and body mass [BM]) and neuromuscular performance (countermovement jump [CMJ] and rebound jumps [RJ]) were assessed. Significant changes following the TMR included RJ mean contact time (RJMCT) (12%, ES=-0.35, P<0.05) and dehydration status increases (BM reductions -2.7%, ES=0.24, P<0.001; Ucol: 147% increase, ES=-1.8, P<0.001). Low to moderate positive correlations were found between pre- and post-TMR BM (r=0.5-0.54; P<0.01), post-race Ucol (r=0.37; P<0.05), age (r=0.57; P<0.01) and TMR performance. Participants' age combined with Ucol and the RJMJH post-TMR, explained 65% of the variance in the final running time (r=0.81; P=0.000). Participation in a 21.1-km TMR in recreational runners results in small reductions of the neuromuscular function and increases in dehydration levels. The hydration status (Ucol) and the RJMJH post-TMR combined with the runners' chronological age seemed to be good predictors of the final running performance.

Adsorption of polymer on an attractive nano-sized particle

The adsorption of a polymer chain on an attractive nano-sized spherical particle is studied by using Monte Carlo simulation. The polymer-particle interaction is treated as Lennard-Jones potential with strength e PP. The critical adsorption point e * PP is estimated from the largest fluctuation of the number of monomers contacted with particle. We find that e * PP is dependent on the comparison between particle size σ p and R G0, the mean radius of gyration of polymer in dilute solution. e * PP decreases with an increase in σ p at σ p < R G0 and is independent of σ p at σ p ≥ R G0. The polymer starts to be adsorbed on particle, and the mean contact time begins to increase at e * PP. In addition, the structural property characterized by trains, loops, and tails is investigated for polymer contacted with particle. Results show that the structure is dependent on the interaction strength e pp. We find that both the number of monomers contacted with the particle and the length of trains increase with e pp, whereas lengths of tail and loop decrease with the increase in e pp.

Trajectories of Early Television Contact in Japan: Relationship with Preschoolers’ Externalizing Problems

We examined the link between trajectories of television contact time at ages 1–5 and externalizing problems at age 5, using data from a Japanese longitudinal study of media use and child development (N = 1,189). Despite the American Academy of Pediatrics recommendation for no television contact before age 2, growth mixture modeling identified 3 trajectory classes, comprising heavy-start contact (8%, mean contact time at age 0 = 331.44 min/day), characterized by remarkably long television contact time in infancy and maintenance of longer contact, while mild contact (51%, 147.57 min/day) and moderate contact (41%, 236.64 min/day) had relatively shorter contact in infancy and moderate declines in later years. The findings suggest that both infant temperamental difficulties and family characteristics predicted trajectory classification of television contact time. Scores for attention problems and conduct problems at age 5 did not significantly differ among trajectory groups, nor did regression coefficients.

Reliability and validity of the Myotest® for measuring running stride kinematics

Accelerometer-based systems are often used to quantify human movement. This study’s aim was to assess the reliability and validity of the Myotest® accelerometer-based system for measuring running stride kinematics. Twenty habitual runners ran two 60 m trials at 12, 15, 18 and 21 km·h−1. Contact time, aerial time and step frequency parameters from six consecutive running steps of each trial were extracted using Myotest® data. Between-trial reproducibility of measures was determined by comparing kinematic parameters from the two runs performed at the same speed. Myotest® measures were compared against photocell-based (Optojump Next®) and high-frequency video data to establish concurrent validity. The Myotest®-derived parameters were highly reproducible between trials at all running speeds (intra-class correlation coefficient (ICC): 0.886 to 0.974). Compared to the photo-cell and high-speed video-based measures, the mean contact times from the Myotest® were 34% shorter and aerial times were 64% longer. Only step frequency was comparable between systems and demonstrated high between-system correlation (ICC ≥ 0.857). The Myotest® is a practical portable device that is reliable for measuring contact time, aerial time and step frequency during running. In terms of validity, it provides accurate step frequency measures but underestimates contact time and overestimates aerial time compared to photocell- and optical-based systems.

Video observation of hand hygiene practices during routine companion animal appointments and the effect of a poster intervention on hand hygiene compliance.

BackgroundHand hygiene is considered one of the most important infection control measures in human healthcare settings, but there is little information available regarding hand hygiene frequency and technique used in veterinary clinics. The objectives of this study were to describe hand hygiene practices associated with routine appointments in companion animal clinics in Ontario, and the effectiveness of a poster campaign to improve hand hygiene compliance.ResultsObservation of hand hygiene practices was performed in 51 clinics for approximately 3 weeks each using 2 small wireless surveillance cameras: one in an exam room, and one in the most likely location for hand hygiene to be performed outside the exam room following an appointment. Data from 38 clinics were included in the final analysis, including 449 individuals, 1139 appointments before and after the poster intervention, and 10894 hand hygiene opportunities. Overall hand hygiene compliance was 14% (1473/10894), while before and after patient contact compliance was 3% (123/4377) and 26% (1145/4377), respectively. Soap and water was used for 87% (1182/1353) of observed hand hygiene attempts with a mean contact time of 4 s (median 2 s, range 1-49 s), while alcohol-based hand rub (ABHR) was used for 7% (98/1353) of attempts with a mean contact time of 8 s (median 7 s, range 1-30 s). The presence of the posters had no significant effect on compliance, although some staff reported that they felt the posters did increase their personal awareness of the need to perform hand hygiene, and the posters had some effect on product contact times.ConclusionsOverall hand hygiene compliance in veterinary clinics in this study was low, and contact time with hand hygiene products was frequently below current recommendations. Use of ABHR was low despite its advantages over hand washing and availability in the majority of clinics. The poster campaign had a limited effect on its own, but could still be used as a component of a multimodal hand hygiene campaign. Improving the infection control culture in veterinary medicine would facilitate future campaigns and studies in this area, as well as overall patient and staff safety.

T Lymphocytes Sense Antigens within Seconds and Make a Decision within One Minute

Adaptive immune responses are triggered by the rapid and sensitive detection of MHC-bound peptides by TCRs. The kinetics of early TCR/APC contacts are incompletely known. In this study, we used total internal reflection fluorescence microscopy to image human T cell membranes near model surfaces: contact was mediated by mobile protrusions of <0.4 μm diameter. The mean lifetime of contacts with a neutral surface was 8.6 s. Adhesive interactions increased mean contact time to 27.6 s. Additional presence of TCR ligands dramatically decreased contact to 13.7 s, thus evidencing TCR-mediated triggering of a pulling motion within seconds after ligand encounter. After an interaction typically involving 30-40 contacts formed during a 1-min observation period, TCR stimulation triggered a rapid and active cell spreading. Pulling events and cell spreading were mimicked by pharmacological phospholipase Cγ1 activation, and they were prevented by phospholipase Cγ1 inhibition. These results provide a quantitative basis for elucidating the earliest cell response to the detection of foreign Ags.

The concurrent effects of strike pattern and ground-contact time on running economy

Running economy is a key determinant of endurance performance, and understanding the biomechanical factors that affect it is of great theoretical and applied interest. This study aimed to analyse how the ground-contact time and strike pattern used by competitive runners concurrently affect running economy. Cross-sectional. Fourteen sub-elite male competitive distance runners completed a 6-min submaximal running trial at 14kmh(-1) on an outdoor track using their habitual strike pattern (n=7 rearfoot strikers: average age, 25.3 years old (SD=2.4); average weight, 64.7kg (SD=5.6); average height, 175.3cm (SD=5.2); n=7 midfoot strikers: average age, 25.0 years old (SD=2.8); average weight, 69.6kg (SD=4.0); average height, 180.1cm (SD=5.1). During the run, the oxygen uptake and ground-contact time were measured. Midfoot strikers showed a significantly shorter (p=0.015) mean contact time (0.228s (SD=0.009)) compared with rearfoot strikers (0.242s (SD=0.010)). Conversely, there was no significant difference (p>0.05) between the groups with respect to mean oxygen uptake (midfoot strikers: 48.4mlmin(-1)kg(-1) (SD=5.3); rearfoot strikers: 49.8mlmin(-1)kg(-1) (SD=6.4)). Linear modelling analysis showed that the effect of contact time on running economy was very similar in the two groups, with a 1ms longer contact time involving an approximately 0.51mlmin(-1)kg(-1) lower oxygen uptake. In contrast, when controlling for contact time, midfoot striking involved an approximately 8.7mlmin(-1)kg(-1) lower oxygen uptake compared with rearfoot striking. When adjusting the foot-ground contact biomechanics of a runner with the aim of maximising running economy, a trade-off between a midfoot strike and a long contact time must be pursued.

Regarding comparison of different techniques of cataract surgery in bacterial contamination of the anterior chamber in diabetic and non-diabetic population

Dear Editor, We read with great interest the authors’ recent report on pre-operative povidone-iodine and ofloxacin instillation in diabetics and non-diabetic patients prior to cataract surgery.[1] The evaluation of antiseptic techniques is particularly important in diabetic patients who may have an increased predisposition to post-operative infection. Evaluating povidone-iodine in diabetic patients is particularly interesting because both can prove to be individually toxic to the cornea. We were interested if the authors did a systematic corneal evaluation as part of their pre-operative and post-operative examination as we did not notice this documented in the study? Diabetes mellitus has been associated with corneal epitheliopathy, decreased corneal oxygen uptake, and altered corneal hysteresis with some evidence suggesting a positive weak correlation with elevated serum glucose levels.[2,3] Povidone-iodine (5%) (PI) has also been associated with toxic corneal epitheliopathy including induction of epithelial cell death and delayed corneal epithelial healing.[4,5] Following pars plana vitrectomy (PPV) for proliferative diabetic retinopathy in poorly controlled diabetics, we have noted a particularly high incidence of peri-operative corneal epitheliopathy. We have speculated that PI and poorly controlled diabetes mellitus may have a synergistic effect in compounding post-operative corneal epitheliopathy. To evaluate this, a retrospective study was conducted of 68 patients who underwent PPV for proliferative diabetic retinopathy. Each patient had thorough pre-operative and post-operative corneal examination, including documentation of fluorescein staining pattern, tear-film breakup time, punctuate epithelial erosions, and epithelial defects. All patients underwent pre-operative preparation with 5% PI to the eyelids, eyelashes, and by flushing the conjunctival fornices with mean contact time of 5 minutes. Fifty percent of eyes developed post-operative corneal epitheliopathy (34 eyes). The average HbA1c for the epitheliopathy group was 8.01% while the average for the non-epitheliopathy group was 8.44%, and this difference was not statistically significant (P = 0.45). There was no statistically significant difference in surgical duration (mean 55 minutes) between patients developing corneal epitheliopathy and not developing corneal epitheliopathy, and there were no cases of endophthalmitis. This study demonstrates a high incidence of corneal epitheliopathy in diabetic patients who underwent PPV for proliferative diabetic retinopathy. There was no correlation between glycosylated hemoglobin levels and corneal epitheliopathy. Further formal studies are warranted to fully investigate this. We would be interested in the authors’ experiences of post-operative corneal evaluation and glycosylated hemoglobin levels from their study, if available.

Interaction dynamics of two colloids in a single optical potential

The interaction of two diffusing particles is strongly influenced by their hydrodynamic coupling. At a tracking rate of 10 kHz we are able to measure the 3D trajectories of two colloidal spheres in a single harmonic potential, which was generated by scanning line optical tweezers. This common potential enables tilting, rotational, and translational dynamics of the spheres, which we analyzed via the spheres position cross-correlations C(τ) over a time range of 10(-4)-2 s. We found that the dynamic interaction of the colloids is controlled by short-range surface forces F(s), which are attractive in one direction and repulsive in the other two directions. This unexpected behavior is supported by a theoretical model using two Langevin equations, which decouple for linear F(s), allowing a description with autocorrelation functions for collective and relative motions. We further demonstrate that variations in salt concentration and reaction volumes significantly influence C(τ) and the mean contact times between the particles, which may offer new insights into biological particle interaction.