Suspending loads decreases load stability but may slightly improve body stability

Here, we seek to determine how compliantly suspended loads could affect the dynamic stability of legged locomotion. We theoretically model the dynamic stability of a human carrying a load using a coupled spring-mass-damper model and an actuated spring-loaded inverted pendulum model, as these models have demonstrated the ability to correctly predict other aspects of locomotion with a load in prior work, such as body forces and energetic cost. We report that minimizing the load suspension natural frequency and damping ratio significantly reduces the stability of the load mass but may slightly improve the body stability of locomotion when compared to a rigidly attached load. These results imply that a highly-compliant load suspension could help stabilize body motion during human, animal, or robot load carriage, but at the cost of a more awkward (less stable) load.     

Ankle and knee moment and power adaptations are elicited through load carriage conditioning in males

Soldiers routinely conduct load carriage and physical training to meet occupational requirements. These tasks are physically arduous and are believed to be the primary cause of musculoskeletal injury. Physical training can help mitigate injury risk when specifically designed to address injury mechanisms and meet task demands. This study aimed to assess lower-limb biomechanics and neuromuscular adaptations during load carriage walking in response to a 10-week evidence-based physical training program. Thirteen male civilian participants donned 23 kg and completed 5 km of load carriage treadmill walking, at 5.5 km h⁻¹ before and after a 10-week physical training program. Three-dimensional motion capture and force plate data were acquired in over-ground walking trials before and after treadmill walking. These data were inputs to a musculoskeletal model which estimated lower-limb joint kinematics and kinetics (i.e., moments and powers) using inverse kinematics and dynamics, respectively. A two-way analysis of variance revealed significant main effect of training for kinematic and kinetics parameters at the knee and ankle joints (p < 0.05). Post-Hoc comparisons demonstrated a significant decrease (4.2%) in total negative knee power between pre- and post-March 5 km measures after training (p < 0.05). Positive power contribution shifted distally after training, increasing at the post-march measure from 39.9% to 43.6% at the ankle joint (p < 0.05). These findings demonstrate that a periodised training program may reduce injury risk through favourable ankle and knee joint adaptations.     

Molecular genetic and phenotypic alteration of Escherichia coli in natural water microcosms containing toxic chemicals

Abstract Microcosms of sterile Chesapeake Bay water were used to study effects of sub-lethal concentrations (1 μl/l) of nitrobenzene, m -cresol, and dibutyl phthalate on Escherichia coli H10407. E. coli remained viable during the 19-day test period in estuarine water, both in the presence and absence of the chemicals, long after it became non-culturable. Analysis of membrane proteins revealed changes in the protein composition. Carbohydrate and amino acid utilization was affected by these changes. Plasmids in E. coli H10407 could not be detected following microcosm exposure. When the cells were transferred to rich medium without toxic chemicals, growth resumed and plasmid bands were again detectable.     

Computational evaluation of load carriage effects on gait balance stability

Evaluating the effects of load carriage on gait balance stability is important in various applications. However, their quantification has not been rigorously addressed in the current literature, partially due to the lack of relevant computational indices. The novel Dynamic Gait Measure (DGM) characterizes gait balance stability by quantifying the relative effects of inertia in terms of zero-moment point, ground projection of center of mass, and time-varying foot support region. In this study, the DGM is formulated in terms of the gait parameters that explicitly reflect the gait strategy of a given walking pattern and is used for computational evaluation of the distinct balance stability of loaded walking. The observed gait adaptations caused by load carriage (decreased single support duration, inertia effects, and step length) result in decreased DGM values (p < 0.0001), which indicate that loaded walking motions are more statically stable compared with the unloaded normal walking. Comparison of the DGM with other common gait stability indices (the maximum Floquet multiplier and the margin of stability) validates the unique characterization capability of the DGM, which is consistently informative of the presence of the added load.     

Discrimination of heterozygous carriage of ataxia-telangiectasia by the method of indirect immunofluorescent analysis

Qualitative differences of the stabilization of protein P53 were studied by methods of indirect immunofluorescence with the use of confocal microscopy in cells obtained from members of the family of a patient with ataxia-telangiectasia (AT)—the proband AT6SP and her blood relatives: the sister AT(S)6SP and the father AT(F)6SP—at different time periods after irradiation with various doses of ionizing radiation.     

Nasal Staphylococcus aureus and S. pseudintermedius carriage in healthy dogs and cats: a systematic review of their antibiotic resistance,virulence and genetic lineages of zoonotic relevance

The molecular ecology of Staphylococcus aureus, Staphylococcus pseudintermedius and their methicillin-resistant strains in healthy dogs and cats could serve as good models to understand the concept of bacterial zoonosis due to animal companionship. This study aims to provide insights into pooled prevalence, genetic lineages, virulence and antimicrobial resistance (AMR) among healthy dogs and cats. Original research and brief communication articles published from 2001 to 2021 that reported the nasal detection of S. aureus and S. pseudintermedius in healthy dogs and cats in the community, homes and outside veterinary clinics were examined and analysed. Forty-nine studies were eligible and included in this systematic review. The pooled prevalence of nasal carriage of S. aureus/methicillin-resistant S. aureus (MRSA) in healthy dogs and cats were 10.9% (95% CI: 10.1–11.9)/2.8% (95% CI: 2.4–3.2) and 3.2% (95% CI: 1.9–4.8)/0.5% (95% CI: 0.0–1.1), respectively. Conversely, the pooled prevalence of S. pseudintermedius/methicillin-resistant S. pseudintermedius (MRSP) in healthy dogs and cats were 18.3% (95% CI: 17.1–19.7)/3.1% (95% CI: 2.5–3.7) and 1.3% (95% CI: 0.6–2.4)/1.2% (95% CI: 0.6–2.3), respectively. Although highly diverse genetic lineages of S. aureus were detected in healthy dogs and cats, MSSA-CC1/CC5/CC22/CC45/CC121/CC398 and MRSA-CC5/CC93/CC22/CC30 were mostly reported in dogs; and MSSA-CC5/CC8/CC15/CC48 and MRSA-CC22/CC30/CC80 in cats. Of note, MSSA-CC398 isolates (spa-types t034 and t5883) were detected in dogs. Genetic lineages often associated with MSSP/MRSP were ST20/ST71, highlighting the frequent detection of the epidemic European MRSP-ST71 clone in dogs. S. aureus isolates carrying the luk-S/F-PV, tst, eta, etb and etd genes were seldomly detected in dogs, and luk-S/F-PV was the unique virulence factor reported in isolates of cats. S. pseudintermedius isolates harbouring the luk-S/F-I, seint and expA genes were frequently found, especially in dogs. High and diverse rates of AMR were noted, especially among MRSA/MRSP isolates. There is a need for additional studies on the molecular characterization of isolates from countries with under-studied nasal staphylococci isolates.     

Backpack load affects lower limb muscle activity patterns of female hikers during prolonged load carriage

This study investigated the effect of prolonged load carriage on lower limb muscle activity displayed by female recreational hikers. Electromyography (EMG) signals from vastus lateralis (VL), biceps femoris (BF), semitendinosus (ST), tibialis anterior (TA) and gastrocnemius (GM) were recorded for fifteen female hikers carrying four loads (0%, 20%, 30% and 40% body weight (BW)) over 8 km. Muscle burst duration, muscle burst onset relative to initial contact and integrated EMG signals (iEMG) were calculated to evaluate muscle activity, whereas the shift in mean power frequency (MPF) was used to evaluate muscle fatigue. Increased walking distance significantly decreased the MPF of TA; decreased the iEMG for VL, ST and GM; and shortened VL muscle burst duration. Furthermore, carrying 20–40% BW loads significantly increased VL and GM iEMG and increased BF muscle burst duration, whereas a 40% BW load caused a later VL muscle burst onset. The differences observed in muscle activity with increased load mass seem to be adjustments aimed at maintaining balance and attenuating the increased loads placed on the lower limbs during gait. Based on the changes in muscle activity, a backpack load limit of 30% BW may reduce the risk of lower limb injury for female hikers during prolonged walking.     

What determines nasal carriage of Staphylococcus aureus?

Nasal carriage of Staphylococcus aureus is an important risk factor for infection by this organism in both community and hospital settings; this article reviews the role of host and bacterial factors in carriage. A host genetic influence appears likely but the phenotypic determinants are unknown. Possibilities include variability in host adhesins, immune response or secretion of antimicrobial molecules. Colonization resistance by S. aureus, together with the observation that persistent carriers often carry a single strain whereas intermittent carriers can be colonized with unrelated strains over time, suggests that bacterial factors could also be involved.     

Superintendence of antimicrobial resistance observed in bacterial flora isolated from human faecal carriage in Vellore,India

A frequent cross-sectional study was conducted to determine the patterns of antimicrobial resistance in 296 bacterial strains isolated from in-patient faecal samples of Government Vellore Medical College and Hospital, Vellore. Isolation and identification of bacterial strains were done using enrichment media, selective media, and biochemical tests. Antimicrobial susceptibility testing by the disc diffusion method and minimal inhibitory concentration method was conducted and the strains were subjected to extended spectrum beta-lactamases screening. Antibiotic sensitivity pattern of Staphylococcus spp. showed oxacillin resistance. Almost all the strains were sensitive to linezolid, vancomycin, gentamycin and chloramphenicol. In gram negative isolates ciprofloxacin and tobramycin showed better sensitivity and ceftazidime showed a higher percentage of resistance by MIC. Out of 250 isolates, Enterobacteriaceae showed positive for 86/250, 82/250 and 94/250 isolates and 3/10, 4/10 and 4/10 non-Enterobacteriaceae isolates were found to be positive for CTX-M gene, TEM gene and SHV gene, respectively. This study helps to assess/analyse the relation between the spectrum of microorganisms present in various grades of faecal carriage and their susceptibility pattern in this part of the Vellore town.     

Spatiotemporal and kinematic changes in gait while carrying an energy harvesting assault pack system

Soldiers are fielded with a variety of equipment including battery powered electronic devices. An energy harvesting assault pack (EHAP) was developed to provide a power source to recharge batteries and reduce the quantity and load of extra batteries carried into the field. Little is known about the biomechanical implications of carrying a suspended-load energy harvesting system compared to the military standard assault pack (AP). Therefore, the goal of this study was to determine the impact of pack type and load magnitude on spatiotemporal and kinematic parameters while walking at 1.34 m/s on an instrumented treadmill at decline, level, and incline grades. There was greater forward trunk lean while carrying the EHAP and the heavy load (decline: p < 0.001; level: p = 0.009; incline: p = 0.003). As load increased from light to heavy, double support stance time was longer (decline: p = 0.012; level: p < 0.001; incline: p < 0.001), strides were shorter (incline: p = 0.013), and knee flexion angle at heel strike was greater (decline: p = 0.033; level: p = 0.035; incline: p = 0.005). When carrying the EHAP, strides (decline: p = 0.007) and double support stance time (incline: p = 0.006) was longer, the knee was more flexed at heel strike (level: p = 0.014; incline: p < 0.001) and there was a smaller change in knee flexion during weight acceptance (decline: p = 0.0013; level: p = 0.007; incline: p = 0.0014). Carrying the EHAP elicits changes to gait biomechanics compared to carrying the standard AP. Understanding how load-suspension systems influence loaded gait biomechanics are warranted before transitioning these systems into military or recreational environments.