Extension Force Research Articles

Numerical Modeling of Conical-Shaped Bone Marrow Biopsy Needle Into Multilayer Iliac Crest Model

Abstract Bone marrow biopsy (BMB) is a standard technique used in various therapies, research, diagnosis, and prognosis. The extensive forces during biopsy result in un-necessary stress concentrations that are primarily hazardous to weak end bones. To enhance protection and to better identify the risks of bone biopsy, it is essential to understand and predict the interaction of needles with multiple layers of skin and bone. The present investigation aimed to find out the numerical evaluation of forces involved in the insertion and extraction of the needle into multilayer iliac crest model. The insertion and extraction forces have been studied at different diameters of biopsy needles up to a depth of 15.35 mm and insertion speeds in the range of 1 mm/s to 10 mm/s. The results showed that the insertion and extraction forces vary according to the needle diameter and relative velocity among the needle and tissue layers. A linear force versus depth relationship has been obtained in the preliminary phase, and as the depth of insertion increases, the forces increase nonlinearly. At the end phase of penetration, the forces augmented more rapidly at a low insertion rate compared to the high insertion rate.

Robot-assisted training with functional electrical stimulation enhances lower extremity function after spinal cord injury.

Functional electrical stimulation (FES) synchronized with robot-assisted lower extremity training is used in spinal cord injury (SCI) rehabilitation to promote residual function. Data of SCI inpatients who trained lower limb mobilization on a stationary robotic system were retrospectively analyzed. The primary outcome was the improvement of muscle strength from the first through to the last training session during FES-induced as well as voluntarily induced flexion and extension. The secondary outcome was the sum score of voluntary muscle function in the lower limbs before and after the training period. Data from 72 patients with SCI (AIS A-D) were analyzed. For extension, FES-assisted strength increased (p < 0.001) from 25.2 to 44.0N, voluntary force (p < 0.001) from 24.4 to 39.9N. For flexion, FES-assisted flexion (p < 0.006) increased from 14.1 to 19.0N, voluntary flexion (p < 0.005) from 12.6 to 17.1N. There was a significant correlation between the increase in FES-assisted force and voluntary flexion (r=0.730, p=0.001) as well as between the increase in FES-assisted force and voluntary extension (r=0.881, p < 0.001). The sum score in muscle test increased from 15 to 24 points. Robot-assisted training with FES seems to support the regeneration of residual functions after SCI. This is evidenced by an improvement in motor function and strength in the lower limbs.

Age-associated Decline In 20-sec Stepping Test Performance In Independent, Community-dwelling Older Women

PURPOSE: To determine if there is an age-related decline in ST performance in independent, community-dwelling women (age 66-89 yrs; n = 1163). METHODS: Subjects completed an eyes open, 20-sec ST and fitness testing. ST measures included head total movement distance (TMD), head greatest placement (MMD), knee total movement distance (KMD) and stepping rate (STEP) determined with a KINECTTM infrared depth sensor. Ratio of KMD/TMD is an index of upper-body sway relative to lower-body. Fitness was defined by self-selected walking speed (NW), fast-walking speed (FW), timed up and go (UPGO), chair stand five-times (CS), and maximum voluntary knee extension force (MVC). Subjects were divided into age groups 65-69 (n = 178), 70-74 (n = 293), 75-79 (n = 417), 80-84 (n = 251), and > 85 (n = 24) yrs and differences examined by ANOVA; significance p < 0.05. Associations between age and ST measures were evaluated using Pearson product moment correlation. RESULTS: Individuals between 75-79 and 85+ groups were shorter, while body mass declined across each group, leveling off at 80 yrs. % body fat was greater, but equal in 80-84 and 85+ groups. TMD was greatest in 80-84 group; all others were similar. TMD and KMD increased in 75-79 through 85+ group. MMD was not different among groups. KMD/TMD was similar and greater in 75-79 and 80-84 yrs, while, 85+ was greater than all groups. Sway per STEP (TMD/KMD/STEP) increased progressively across groups. There was a progressive reduction in fitness variables beginning with 75-79 group. ST variables, except MMD, were significantly correlated with age, but coefficients were low (r = -0.23-0.12, p < 0.05). CONCLUSIONS: Age-related decline in ST performance observed primarily as a progressive increase in sway (KMD/TMD, and KMD/TMD/STEP) indicates reduced balance in accordance with our previous findings. Progressive reduction in static/dynamic balance negatively affects physical function (e.g. decrements in walking speed, TUG etc.) as observed here. This supports our recent findings that ST differentiates physical disability, indicates risk of falling, and “need for assistance”. Supported by JSPS (Grant number: 20 K11656)

Chromatin fiber breaks into clutches under tension and crowding.

The arrangement of nucleosomes inside chromatin is of extensive interest. While in vitro experiments have revealed the formation of 30 nm fibers, most in vivo studies have failed to confirm their presence in cell nuclei. To reconcile the diverging experimental findings, we characterized chromatin organization using a residue-level coarse-grained model. The computed force–extension curve matches well with measurements from single-molecule experiments. Notably, we found that a dodeca-nucleosome in the two-helix zigzag conformation breaks into structures with nucleosome clutches and a mix of trimers and tetramers under tension. Such unfolded configurations can also be stabilized through trans interactions with other chromatin chains. Our study suggests that unfolding from chromatin fibers could contribute to the irregularity of in vivo chromatin configurations. We further revealed that chromatin segments with fibril or clutch structures engaged in distinct binding modes and discussed the implications of these inter-chain interactions for a potential sol–gel phase transition.

Experimental-numerical analysis of the fracture process of Al-Al-Ti laminated composite

In the paper presented a study of the fracture process of explosive welded layered material AA2519-AA1050-Ti6Al4V (Al-Al-Ti laminate) at ambient (+20 °C) and reduced (−50 °C) temperatures. The tensile tests and fracture toughness tests were conducted for both types specimens made of base materials plates and of laminated plate. During tensile tests performed on flat specimens the signals of loading force (P) and specimen extension (uext) were recorded. The signals of loading force (P), specimen deflection (udef) and the crack mouth opening displacement (COD) were recorded while performing the tests on fracture toughness of materials on SENB type specimens. The breakthroughs of the tested specimens were observed by scanning electron microscope (SEM).The results obtained during the experimental tests indicate the complicated nature of the cracking process of specimens from the Al-Al-Ti laminate. The deviation from linearity was observed during loading on the sections where it should be linear. There were also slightly decreases in the force value during the load. During macro observation of the fractured surfaces of SENB specimens, delamination cracks between the Al and Ti layers are clearly visible. The size of these cracks increases as the test temperature decreases. The SEM observations clearly indicate that the delamination crack is formed in the AA1050 layer joining the Ti6Al4V and AA2519 base materials. Precise observation by SEM allowed to establish that the development of a delamination crack begins with different type of particles fracture and material discontinuous in narrow strip (20–40 mm) near at Ti6Al4V material. Then the delamination crack develops in the layer of AA1050 material according to a shear mechanism.In order determine the stress and strain distributions in tested specimens the they numerical models were developed and simulation of loading were performed by ABAQUS program. The results of stress and strain distributions obtained clearly shows on large differences they values in the different layers of the laminate. Maximal differences of stress levels occurs between layers Ti6Al4V and AA1050 materials. Due to the fact that the material of the connecting layer (AA1050) has a low level of yield strength, a very high level of plastic strain occurs.Based on the results obtained during the experimental tests, SEM observation of fracture surfaces and numerical calculations, it can be concluded that the weakest area in the tested laminate is the connecting layer AA1050. Namely is it, a thin strip between AA1050 and Ti6Al4V, which consists of metal base particles, intermetallic compounds, their oxides and discontinuities of the material in form of voids.When using this type of laminate, special attention should be paid to the strength of the AA1050 bonding layer.

Effect of an Isometric or Eccentric Hip Extension Exercise Intervention on Hamstring Strength, Architecture, and Morphology.

This study aimed to investigate hamstring architectural, strength, and morphological adaptations after an eccentric or isometric hip extension exercise intervention. Twenty-four recreationally active males performed either an eccentric ( n = 12) or an isometric hip extension ( n = 12) exercise intervention, twice per week for 6 wk, followed by a 4-wk detraining period. Biceps femoris long head (BFlh) architecture was assessed pre-intervention, mid-intervention, post-intervention, and post-detraining via two-dimensional ultrasound. Strength was assessed pre-intervention, post-intervention, and post-detraining during an isokinetic knee flexion, an isometric hip extension, a Nordic hamstring exercise, and a single-leg hamstring bridge repetition to fatigue test. Hamstring muscle morphology was assessed via magnetic resonance imaging before strength testing sessions. The eccentric hip extension exercise intervention significantly lengthened BFlh fascicles (+19.7%, P < 0.001, d = 1.57), increased eccentric knee flexion torque (ECC 60°·s -1 , +12%, P < 0.005, d = 0.66; ECC 180°·s -1 , +8.3%, P < 0.05, d = 0.41), and increased BFlh (+13.3%, P < 0.001, d = 1.96) and semimembranosus (SM) muscle volume (+12.5%, P < 0.001, d = 2.25). After 4 wk of detraining, BFlh fascicles were significantly shortened in the eccentric group (-14.8%, P < 0.005, d = -1.25), whereas eccentric knee flexion torque and BFlh and SM volumes were unchanged. The isometric hip extension exercise intervention significantly increased isometric knee flexion torque (+10.4%, P < 0.05, d = 0.54), isometric hip extension force (+12.4%, P < 0.05, d = 0.41), and semitendinosus volume (+15%, P = 0.054, d = 1.57). All other outcome measures saw no significant changes. After 4 wk of detraining, no significant changes to any variables were observed in the isometric group. The eccentric but not isometric hip extension exercise intervention significantly increased BFlh fascicle length. Both exercise interventions demonstrated contraction mode-specific increases in strength. However, the eccentric hip extension exercise intervention resulted in preferential hypertrophy of BFlh and SM, and the isometric hip extension exercise intervention led to selective hypertrophy of semitendinosus.

Satisfaction and Functional Outcome of Surgical Treatment in Patients with Brachial Plexus Injury: A Decade of Retrospective Comparative Study.

Brachial plexus injury (BPI) is a severe peripheral nerve injury resulting in physical disability. Few studies have investigated the postoperative functional status. We aimed to evaluate the satisfaction with surgical treatment in patients with BPI referred to the Panzdah-e Khordad Hospital, Tehran, Iran from 2011 to 2021. In this descriptive-analytical retrospective comparative study, physical examination, along with BrAT, and DASH questionnaires were used to evaluate the patients' status. Then the collected data on the patients' functional status and movements were collected. To compare the mean of quantitative variables before and after the surgery, the dependent t-student was used. Generally, the patients stated that they still had considerable difficulty doing most of the items of the questionnaires. Nevertheless, there was a significant difference between the following variables before and after surgery; shoulder abduction goniometry (0-150) and force (M0:M5), shoulder external rotation goniometry (0-90) and force (M0:M5)), shoulder forward flexion goniometry (0-180) and force (M0:M5)), elbow flexion goniometry (0- 150), elbow extension force (M0:M5), and wrist and finger muscle force (M0:M5) (P<0.001). Posterior approach in BPI surgery was associated with good outcomes in terms of shoulder external rotation and abduction. However, patients still suffered from difficulties in daily activities.

KNEE extension lag

In a study involving 34 patients, researchers looked at how knee extension lag correlated with other measures of injured and healthy limbs. The average flexion force was found to be greater than the average extension force in the injured extremity, and there was no difference between the means of flexion and extension force. This study also found that the extension lag was unrelated to squatting depth, extension force, flexion force, circumference at the joint line, circumference 5 and 15 centimeters cephalad to the patella pole, and active or passive knee flexion. When compared to a control group of patients with healthy rotational movements, these medians showed significant variation. Comparisons between patient groups suggest a connection between quadriceps weakness and knee extension lag, but no other factors have been found to correlate with this finding. Researchers recommend recruiting participants with extension lags greater than 30 in order to increase the likelihood of discovering such links.

Thermodynamics of Extra-Toughness and Hidden-Length in Polymeric Materials with Sacrificial Bonds

Sacrificial bonds have been observed in several biological materials and structures and can increase their toughness, i.e., their resistance to fracture. They provide a reversible mechanism for dissipating mechanical energy before the possible system rupture. From a structural point of view, sacrificial bonds consist of short polymer chains that short-circuit parts of a main macromolecular chain (generating hidden lengths) and absorb energy by breaking them instead of the main chain. The toughness increase due to the presence of sacrificial bonds is typically named extra-toughness. Here, we developed a statistical mechanics and thermodynamics-based theory able to estimate the force–extension relation for chains with sacrificial bonds and to calculate the corresponding extra-toughness. The model is useful to better understand the sacrificial bond effects in biomaterials but also to apply the biomimetic paradigm and foster the development of high-performance artificial polymeric materials.

General, spinal or regional anaesthesia does not affect strength performance 6 months after ACL reconstruction

PurposeThe recovery of strength is a key element in successfully returning to sports after ACL reconstruction. The type of anaesthesia has been suspected an influential factor in the post-operative recovery of muscle function.MethodsIn this retrospective analysis, n = 442 consecutive patients undergoing primary isolated ACL reconstruction using a hamstring autograft were analysed by pre- and post-operative isokinetic tests in a single orthopaedic centre. These were subdivided into four cohorts: (1) general anaesthesia (n = 47), (2) general anaesthesia with prolonged (48 h) on-demand femoral nerve block (n = 37), (3) spinal anaesthesia (n = 169) and (4) spinal anaesthesia with prolonged (48 h) on-demand femoral nerve block (n = 185). Primary outcome was the change from pre- to post-operative isokinetic strength during knee extension and flexion.ResultsUsing one-way ANOVA, there was no significant influence of the type of anaesthesia. The main effect of anaesthesia on change in extension forces was not significant, and effect sizes were very small (n.s.). Similarly, the main effect of anaesthesia on change in flexion forces was statistically not significant (n.s.).ConclusionsThe findings of this study support the interpretation that the type of anaesthesia has no significant effect on the ability to recover thigh muscle strength 6 months after isolated hamstring ACL reconstruction. With regard to the recovery of athletic performance and return-to-sports testing criteria, there is no reason to avoid regional anaesthesia.Level of evidenceIII.

Association of phase angle with muscle function and prognosis in patients with head and neck cancer undergoing chemoradiotherapy

ObjectivesThe aims of this study were to investigate the correlation of phase angle (PhA) with other parameters (e.g., muscle mass/quality/strength and physical function), assess the prognostic relevance of prechemoradiotherapy (CRT) PhA, and suggest a reference value of PhA in Asian patients with head and neck cancer (HNC). MethodsNinety-six patients with HNC who underwent CRT were divided into two groups— maintained-PhA group and low-PhA group—according to the PhA 25th percentile values by sex. Pretreatment PhA was measured using direct segmental multifrequency bioelectrical impedance analysis, and muscle quality was assessed using echo intensity in ultrasound images. Correlation of PhA with other parameters was investigated, and between-group differences with respect to adverse events, treatment interruption, and 3-y survival were assessed. ResultsPhA showed a positive correlation with isometric knee extension force (R = 0.710), handgrip strength (R = 0.649), skeletal muscle mass index (R = 0.620), and maximum gait speed (R = 0.543; P < 0.001). PhA showed a negative correlation with echo intensity (R = −0.439) and five times sit-to-stand test (R = −0.505; P < 0.01). The low-PhA group had a higher incidence of severe anemia (52% in low-PhA versus 17% in maintained-PhA), aspiration (17 versus 1%), radiotherapy interruption (17 versus 3%), and poor 3-y survival (47 versus 81%) than the maintained-PhA group (P < 0.05). ConclusionPhA was correlated with muscle mass/quality/strength, and physical function. Low PhA was associated with severe adverse events, treatment interruption, and shorter survival. These findings suggested that 4.6° for men and 4° for women may be useful as prognostic reference values in Asian patients with HNC.

The association of posterior tibial slope changes between joint gap contact force and the range of motion in Oxford mobile bearing unicompartmental knee arthroplasty

Objective: To investigate the correlation between the change of posterior tibial slope (PTS) after unicompartmental knee arthroplasty (UKA) and the contact force at the end stage of knee flexion and extension, as well as the postoperative range of motion. Methods: The data of 38 cases (46 knees) of UKAs undertaken in China-Japan Friendship Hospital from June 2020 to June 2021 were analyzed in this study. A custom-designed force sensor was used to measure gap contact force in the medial gap of UKA. The correlations between each two of the three factors-the change of PTS (∆PTS), the gap contact force of full extension and deep flexion and the range of knee motion were analyzed. Results: Totally of 38 patients (46 knees) were enrolled, including 14 males and 24 females, aged (69.1±7.4) years, with an average follow-up of (11.2±3.7) months. The average gap contact force was (88.3±40.6)N, the adjusted contact force of the full extension gap was 81.7%±33.8%, while that of the deep flexion gap was 55.6%±31.0%. At the last follow-up, the fixed flexion degree[M(Q1, Q3)] was 0°(0°, 3°), which was significantly lower than the preoperative value of 0°(0°, 5°) (P<0.05); the postoperative max flexion degree was 115.9°±16.4°, it was increased when compared with the preoperative value of 112.0°±16.8° (P<0.05); and the postoperative PTS was 8.3°±2.7°, and there was no significant difference with the preoperative value (8.6°±2.1°,P>0.05). There was a positive correlation between ∆PTS and both the contact force of full extension gap and the fixed flexion degree (r=0.334 and 0.317, P<0.05). Besides, there was a negative correlation between ∆PTS and the contact force of the deep flexion gap (r=-0.397, P<0.05). However, the correlations between these two factors and the max flexion degree were not significant (P>0.05). Conclusions: The reduction of PTS in UKA would reduce the contact force of the full extension gap, as well as the postoperative fixed flexion deformity. Besides, it could increase the contact force of the deep flexion gap, but would not influence the max flexion degree of the knee postoperatively.

Research on the Protection of Extensor and Flexor Muscles in the Waist and Back of Competitive Athletes.

In the past, in the study of special sports quality of heavy antagonistic sports events, the study of strength quality training was emphasized. The transformation of athletes' strength quality to special strength was highlighted, and the special exercises which tended to be consistent with the characteristics of wrestling events were added. However, in competition and training, athletes' spine bears a heavy load. Long-term static contraction of lumbar muscles can lead to excessive local load and injury of lumbar muscles. In this paper, the test results of athletes' joints are analyzed, and the waist protection scheme for athletes' strength training is obtained. First of all, solve the problem of athletes' action mode and improve athletes' muscle endurance. All special sports quality evaluation can reach a good level. Then, enhance athletes' explosive power. Thus, all special sports quality evaluations can reach an excellent level. It is concluded that the waist and back are the key parts to support their participation in various sports, maintain body balance, and realize power transmission. Through the study, it is found that there are significant differences in the muscle strength indexes of the maximum strength of the waist and back of athletes of different levels, which fully proves the characteristics of the maximum strength of the waist and back. Through the test, we can understand the flexion and extension strength, range, speed, force, and flexion and extension ratio of athletes' joints and take timely optimization measures according to the test results to avoid sports injuries in training. It has a key guiding significance for the measurement, analysis, and evaluation of athletes' joint muscle strength, as well as rehabilitation training after injury and prevention of reinjury.

Estimation of Knee Extension Force Using Mechanomyography Signals Based on GRA and ICS-SVR

During lower-extremity rehabilitation training, muscle activity status needs to be monitored in real time to adjust the assisted force appropriately, but it is a challenging task to obtain muscle force noninvasively. Mechanomyography (MMG) signals offer unparalleled advantages over sEMG, reflecting the intention of human movement while being noninvasive. Therefore, in this paper, based on MMG, a combined scheme of gray relational analysis (GRA) and support vector regression optimized by an improved cuckoo search algorithm (ICS-SVR) is proposed to estimate the knee joint extension force. Firstly, the features reflecting muscle activity comprehensively, such as time-domain features, frequency-domain features, time–frequency-domain features, and nonlinear dynamics features, were extracted from MMG signals, and the relational degree was calculated using the GRA method to obtain the correlation features with high relatedness to the knee joint extension force sequence. Then, a combination of correlated features with high relational degree was input into the designed ICS-SVR model for muscle force estimation. The experimental results show that the evaluation indices of the knee joint extension force estimation obtained by the combined scheme of GRA and ICS-SVR were superior to other regression models and could estimate the muscle force with higher estimation accuracy. It is further demonstrated that the proposed scheme can meet the need of muscle force estimation required for rehabilitation devices, powered prostheses, etc.

Allogeneic haematopoietic stem cell transplantation and patient falls: impact of lower extremity muscle strength.

Patients undergoing allogeneic haematopoietic stem cell transplantation (allo-HSCT) have a higher risk of falls than those receiving other therapies for haematological disorders. This study aimed to investigate the impact of pretransplant lower extremity muscle strength (LEMS) on post-transplant falls. In this retrospective cohort study, patients aged ≥18 years who underwent allo-HSCT were included. All data were extracted from medical records. LEMS was defined as the knee extension force measured by a handheld dynamometer divided by the patient's weight. The receiver operating characteristic (ROC) curve was used to calculate the optimal LEMS cut-off value for prediction of falls. Patients were categorised into low and normal LEMS groups based on the cut-off value. The impact of pretransplant LEMS on post-transplant falls was analysed using a Cox proportional hazards model. In total, 101 patients were analysed. During the observation period, falls occurred in 32 patients (31.7%). The ROC curve analysis results showed that the optimal LEMS cut-off value for prediction of falls was 45.4% per body weight. In multivariate analysis, pretransplant low LEMS was a significant predictor of falls in model 1 with patient characteristics as a confounding factor and model 2 with medications-inducing falls as a confounding factor, respectively (model 1: HR 3.23, 95% CI 1.37 to 7.64; model 2: HR 2.82, 95% CI 1.20 to 6.59). Pretransplant LEMS was a significant predictor of post-transplant falls. The results of this study may help to prevent falls in patients undergoing allo-HSCT.

Thermomechanical analysis of the effect of contact forces in heat conduction of composite materials through multiscale contact finite element modeling

The present study proposes a thermomechanical surface contact finite element formulation for studying interfacial heat conductance in correlation to micromechanical contact forces. The proposed methodology is applied for modeling heat surface conductivity of Carbon Nanotubes (CNT). The atomic lattice of CNTs is initially modeled using the molecular structural mechanics approach and reduced to an equivalent 2D continuum element. The equivalent 2D continuum element is used as a robust and efficient surrogate model for the construction of full length CNTs in contact. Coupled structural and heat pde’s have been used to describe the corresponding thermomechanical problem which are discretized using 2D quadrilateral finite elements, along with surface contact elements based on the Node to Node and Node to Segment formulations. The problem has been treated as a nonlinear steady state problem and solved in the frame of a Newton-Raphson incremental-iterative scheme. Extensive sensitivity analysis was performed with respect to several influencing parameters, such as initial contact angle, boundary conditions and CNT overlapping. Based on this analysis, the effect of overlapping and approaching angle on the total heat exchange was quantified. It has been demonstrated that in most cases, increasing the total contact force can produce an almost linear increase in heat exchange. However, in cases of small approaching angles between CNTs an extensive contact force could heavily deform the contacting geometries producing a non-linear heat exchange mechanism.

Assessing isometric kicking force and post-match responses using the Kicker test

ABSTRACT This study examined the inter-session reliability of force output from a novel isometric strength assessment protocol (the Kicker); and its suitability to monitor soccer player’s combined hip flexion and knee extension force capacity over 72-h post-competitive matches. Reliability (Part-A) testing was completed over three sessions on 20 individuals participating in various sports at a recreational level or higher. Post-match strength response (Part-B) data were collected for 72-h after a game (24-h (+24), 48-h (+48) and 72-h (+72) post-match) in 17 male academy soccer players. After familiarisation, Kicker force for each limb showed high inter-session reliability (ICC >0.95; typical error <14 N, CV <6%); minimum detectable change at a 95% confidence interval <40 N). Across the 72-h post-match period, Kicker force for each limb was suppressed compared to baseline (force loss range = −5.8% to −12.5%; effect sizes range = −0.26 to −0.43) at all time points. The Kicker assessment protocol measures combined isometric hip flexor and knee extensor force capacity with high inter-session reliability. The proof of concept that the protocol can be used as a monitoring tool was evidenced by sustained suppression of baseline force capacity in both kicking limbs for 72-h post soccer matches.

Thermal control of nucleation and propagation transition stresses in discrete lattices with non-local interactions and non-convex energy

Non-local and non-convex energies represent fundamental interacting effects regulating the complex behavior of many systems in biophysics and materials science. We study one-dimensional, prototypical schemes able to represent the behavior of several biomacromolecules and the phase transformation phenomena in solid mechanics. To elucidate the effects of thermal fluctuations on the non-convex non-local behavior of such systems, we consider three models of different complexity relying on thermodynamics and statistical mechanics: (i) an Ising-type scheme with an arbitrary temperature-dependent number of interfaces between different domains, (ii) a zipper model with a single interface between two evolving domains, and (iii) an approximation based on the stationary phase method. In all three cases, we study the system under both isometric condition (prescribed extension, matching with the Helmholtz ensemble of the statistical mechanics) and isotensional condition (applied force, matching with the Gibbs ensemble). Interestingly, in the Helmholtz ensemble the analysis shows the possibility of interpreting the experimentally observed thermal effects with the theoretical force–extension relation characterized by a temperature-dependent force plateau (Maxwell stress) and a force peak (nucleation stress). We obtain explicit relations for the configurational properties of the system as well (expected values of the phase fractions and number of interfaces). Moreover, we are able to prove the equivalence of the two thermodynamic ensembles in the thermodynamic limit. We finally discuss the comparison with data from the literature showing the efficiency of the proposed model in describing known experimental effects.

Single-Molecule Micromanipulation and Super-Resolution Imaging Resolve Nanodomains Underlying Chromatin Folding in Mitotic Chromosomes.

The folding of interphase chromatin into highly compact mitotic chromosomes is one of the most recognizable changes during the cell cycle. However, the structural organization underlying this drastic compaction remains elusive. Here, we combine several super resolution methods, including structured illumination microscopy (SIM), binding-activated localization microscopy (BALM), and atomic force microscopy (AFM), to examine the structural details of the DNA within the mitotic chromosome, both in the native state and after up to 30-fold extension using single-molecule micromanipulation. Images of native chromosomes reveal widespread ∼125 nm compact granules (CGs) throughout the metaphase chromosome. However, at maximal extensions, we find exclusively ∼90 nm domains (mitotic nanodomains, MNDs) that are unexpectedly resistant to extensive forces of tens of nanonewtons. The DNA content of the MNDs is estimated to be predominantly ∼80 kb, which is comparable to the size of the inner loops predicted by a recent nested loop model of the mitotic chromosome. With this DNA content, the total volume expected of the human genome assuming closely packed MNDs is nearly identical to what is observed. Thus, altogether, these results suggest that these mechanically stable MNDs, and their higher-order assembly into CGs, are the dominant higher-level structures that underlie the compaction of chromatin from interphase to metaphase.

Dynamic correction of ulnar claw hand deformity with a simple insertion into the lumbrical muscle

Numerous methods of tendon transfers are available to correct claw hand deformity. In this article, we describe a simple insertion of the transferred flexor digitorum superficialis tendon, into the lumbrical muscle and proximal tendon. Sixty patients underwent surgery for claw hand correction. These were equally divided into three groups undergoing; modified Stiles Bunnell procedure; 'lasso' insertion into A1 pulley and the lumbrical insertion procedure. Evaluation was done with proximal interphalangeal joint angle measurements, grip strength and using the Brand's criteria, 1 year after surgery. The improvements were comparable among the three groups. Insertion into the lateral bands has been a standard method of claw correction. In addition to correcting the hyperextension of the metacarpophalangeal joint, it transmits force for interphalangeal joint extension and restores the sequence of flexion of fingers, thus making the grasp effective. Insertion into the lumbrical muscle belly and proximal tendon shows similar results. It can be performed via a single incision in the palm, reducing operative time.