Three-dimensional quantification of pretorqued nickel-titanium wires in edgewise and prescription brackets

OBJECTIVE

To quantify the three-dimensional moments and forces produced by pretorqued nickel-titanium (NiTi) rectangular archwires fully engaged in 0.018- and 0.022-inch slots of central incisor and molar edgewise and prescription brackets.

MATERIALS AND METHODS

Ten identical acrylic dental models with retroclined maxillary incisors were fabricated for bonding with various bracket-wire combinations. Edgewise, Roth, and MBT brackets with 0.018- and 0.022-inch slots were bonded in a simulated 2 × 4 clinical scenario. The left central incisor and molar were sectioned and attached to load cells. Correspondingly sized straight and pretorqued NiTi archwires were ligated to the brackets using 0.010-inch ligatures. Each load cell simultaneously measured three force (Fx, Fy, Fz) and three moment (Mx, My, Mz) components. The faciolingual, mesiodistal, and inciso-occluso/apical axes of the teeth corresponded to the x, y, and z axes of the load cells, respectively. Each wire was removed and retested seven times. Three-way analysis of variance (ANOVA) examined the effects of wire type, wire size, and bracket type on the measured orthodontic load systems. Interactions among the three effects were examined and pair-wise comparisons between significant combinations were performed.

RESULTS

The force and moment components on each tooth were quantified according to their local coordinate axes. The three-way ANOVA interaction terms were significant for all force and moment measurements (P < .05), except for Fy (P > .05).

CONCLUSION

The pretorqued wire generates a significantly larger incisor facial crown torquing moment in the MBT prescription compared to Roth, edgewise, and the straight NiTi wire.

RhoA goes GLOBAL

Mechanical forces influence nearly all aspects of biology. Cells are equipped with numerous mechanosensitive proteins that activate various signaling cascades in response to mechanical cues from their environment. Much interest lies in understanding how cells respond to external stresses. A number of studies have highlighted the coordination of mechanical and chemical signaling cascades downstream of integrins. In recent years, the study of mechanotransduction has expanded to other mechanosensitive adhesion receptors, such as platelet endothelial cell adhesion molecule-1 (PECAM-1). This commentary will highlight our current understanding of integrin and PECAM-1-mediated mechanotransduction and expand on the observation that a localized mechanical stress can elicit a global mechanosignaling response.

Does a basic deficit in force control underlie cerebellar ataxia?

Because damage to the cerebellum results in characteristic movement incoordination known as "ataxia," it has been hypothesized that it is involved in estimation of limb dynamics that occur during movement. However, cerebellar function may extend beyond movement to force control in general, with or without movement. Here we tested whether the cerebellum is involved in controlling force separate from estimating limb dynamics and whether ataxia could result from a deficit in force control. We studied patients with cerebellar ataxia controlling their arm force isometrically; in this condition arm dynamics are absent and there is no need for (or effect from an impairment in) estimations of limb dynamics. Subjects were required to control their force magnitude, direction, or both. Cerebellar patients were able to match force magnitude or direction similarly to control subjects. Furthermore, when controlling force magnitude, they intuitively chose directions (not specified) that required minimal effort at the joint level--this ability was also similar to control subjects. In contrast, cerebellar patients performed significantly worse than control subjects when asked to match both force magnitude and direction. This was surprising, since they did not exhibit significant impairment in doing either in isolation. These results show that cerebellum-dependent computations are not limited to estimations of body dynamics needed for active movement. Deficits occur even in isometric conditions, but apparently only when multiple degrees of freedom must be controlled simultaneously. Thus a fundamental cerebellar operation may be combining/coordinating degrees of freedom across many kinds of movements and behaviors.

Examining the interaction of force and repetition on musculoskeletal disorder risk: a systematic literature review

OBJECTIVE

Our aims were (a) to perform a systematic literature review of epidemiological studies that examined the interaction of force and repetition with respect to musculoskeletal disorder (MSD) risk, (b) to assess the relationship of force and repetition in fatigue failure studies of musculoskeletal tissues, and (c) to synthesize these findings.

BACKGROUND

Many epidemiological studies have examined the effects of force and repetition on MSD risk; however, relatively few have examined the interaction between these risk factors.

METHOD

In a literature search, we identified 12 studies that allowed evaluation of a force-repetition interaction with respect to MSD risk. Identified studies were subjected to a methodological quality assessment and critical review. We evaluated laboratory studies of fatigue failure to examine tissue failure responses to force and repetition.

RESULTS

Of the 12 epidemiological studies that tested a Force x Repetition interaction, 10 reported evidence of interaction. Based on these results, the suggestion is made that force and repetition may be interdependent in terms of their influence on MSD risk. Fatigue failure studies of musculoskeletal tissues show a pattern of failure that mirrors the MSD risk observed in epidemiological studies.

CONCLUSIONS

Evidence suggests that there may be interdependence between force and repetition with respect to MSD risk. Repetition seems to result in modest increases in risk for low-force tasks but rapid increases in risk for high-force tasks. This interaction may be representative of a fatigue failure process in affected tissues.

Characterization of the mechanical properties of qPlus sensors

In this paper we present a comparison of three different methods that can be used for estimating the stiffness of qPlus sensors. The first method is based on continuum theory of elasticity. The second (Cleveland's method) uses the change in the eigenfrequency that is induced by the loading of small masses. Finally, the stiffness is obtained by analysis of the thermal noise spectrum. We show that all three methods give very similar results. Surprisingly, neither the gold wire nor the gluing give rise to significant changes of the stiffness in the case of our home-built sensors. Furthermore we describe a fast and cost-effective way to perform Cleveland's method. This method is based on gluing small pieces of a tungsten wire; the mass is obtained from the volume of the wire, which is measured by optical microscopy. To facilitate detection of oscillation eigenfrequencies under ambient conditions, we designed and built a device for testing qPlus sensors.

Measurement of osteotomy force during endoscopic sinus surgery

Greater understanding of the surgeon's task and skills are required to improve surgical technique and the effectiveness of training. Currently, neither the objective measurement of osteotomy forces during endoscopic sinus surgery (ESS) nor the validity of the properties of cadaver materials, are well documented. Measurement was performed of peak axial osteotomy force during ESS. A comparison was made of results with previously published cadaver data to validate the force properties of cadaver models. A prospective, consecutive cohort of 25 patients was compared with data from 15 cadaver heads. A modified Storz sinus curette measured osteotomy force from uncinate, bulla ethmoidalis, and ground lamella. Independent variables were osteotomy site, age, gender, indication for surgery, and side. Corresponding cadaver data were analyzed for the independent variables of osteotomy site, side, and gender and then compared with the live patient data. Mean osteotomy force in live patients was 9.6 N (95% CI, 8.9–10.4 N). Mean osteotomy force in the cadaver heads was 6.4 N (95% CI, 5.7–7.0 N). Ethmoid osteotomy of live patients required 3.2 N (95% CI, 2.1–4.3 N) more force than the cadaver heads (p = 0.0001). This relationship was statistically significant at the bulla ethmoidalis (p = 0.002) and the ground lamella (p = 0.0001) but not at the uncinate (p = 0.068). Osteotomy in female live subjects required 1.6 N (95% CI, 0.1–3.1 N) more force than male live subjects (p = 0.03). Cadaver tissue may underestimate the mean osteotomy force required in osteotomy of living ethmoid sinus lamellae by a factor of 1.5 times. Caution may be required in extrapolating force estimates from cadaver tissue to those required in living patients.

Ovarian cancer spheroids use myosin-generated force to clear the mesothelium

Dissemination of ovarian tumors involves the implantation of cancer spheroids into the mesothelial monolayer on the walls of peritoneal and pleural cavity organs. Biopsies of tumors attached to peritoneal organs show that mesothelial cells are not present under tumor masses. We have developed a live, image-based in vitro model in which interactions between tumor spheroids and mesothelial cells can be monitored in real time to provide spatial and temporal understanding of mesothelial clearance. Here we provide evidence that ovarian cancer spheroids utilize integrin- and talin- dependent activation of myosin and traction force to promote mesothelial cells displacement from underneath a tumor cell spheroid. These results suggest that ovarian tumor cell clusters gain access to the sub-mesothelial environment by exerting force on the mesothelial cells lining target organs, driving migration and clearance of the mesothelial cells.

A Wireless, Passive Load Cell based on Magnetoelastic Resonance

A wireless, battery-less load cell was fabricated based on the resonant frequency shift of a vibrating magnetoelastic strip when exposed to an AC magnetic field. Since the vibration of the magnetoelastic strip generated a secondary field, the resonance was remotely detected with a coil. When a load was applied to a small area on the surface of the magnetoelastic strip via a circular rod applicator, the resonant frequency and amplitude decreased due to the damping on its vibration. The force sensitivity of the load cell was controlled by changing the size of the force applicator and placing the applicator at different locations on the strip's surface. Experimental results showed the force sensitivity increased with a larger applicator placing near the edge of the strip. The novelty of this load cell is not only its wireless passive nature, but also the controllability of the force sensitivity.

Microfiber-based Bragg gratings for sensing applications: a review

Microfiber-based Bragg gratings (MFBGs) are an emerging concept in ultra-small optical fiber sensors. They have attracted great attention among researchers in the fiber sensing area because of their large evanescent field and compactness. In this review, the basic techniques for the fabrication of MFBGs are introduced first. Then, the sensing properties and applications of MFBGs are discussed, including measurement of refractive index (RI), temperature, and strain/force. Finally a summary of selected MFBG sensing elements from previous literature are tabulated.

In Vitro System for Measuring Chordal Force Changes Following Mitral Valve Patch Repair

BACKGROUND

Attention towards optimization of mitral valve repair methods is increasing. Patch augmentation is one strategy utilized to correct functional mitral regurgitation or systolic anterior motion in complex mitral valve repairs. This article describes a system for investigating the redistribution of chordae tendineae tension as a reflection of altered stress distribution of the valve leaflet following patch augmentation.

METHODS AND MATERIALS

An in vitro test setup was constructed to hold native porcine mitral valves containing an annulus and papillary muscle positioning system. The alterations caused by patch augmentation should be visual from both the atrial and ventricular views. Ventricular pressure was regulated stepwise in a range of 0-150 mmHg. To test the system, the anterior mitral leaflet was extended by a pericardial patch sutured to the mid/basal part of the leaflet, and the chordae tendineae force was measured as the ventricular pressure was applied.

RESULTS

The system demonstrated the capacity to hold native porcine mitral valves and introducing patch repairs according to clinical practice. The porcine mitral valve test setup indicated strong correlation between the forces in the mitral valve secondary chordae tendineae and the applied transvalvular pressure (R² = 0.95).

CONCLUSION

This test setup proved the ability to obtain normal mid-systolic mitral valve function, secondary chordae force measurements, and important preservation of the visual access: Hence, obtaining the pressure-force relationship as well as identifying any shift of the secondary chordae insertion point on the anterior leaflet relative to the coaptation zone was made possible.

How does viral DNA find the nucleus of an infected cell?

If all locations of a living cell would have the same chemical potential, most viral infections of a cell should be abortive, even after the a penetration of the cell wall by the viral DNA-polymer or viral RNA-polymer occurred. This is obviously not the case. Therefore, there must be a mechanism which transports a viral DNA-polymer from the cell wall to the nucleus and not to any other location. A possible mechanism is proposed which is in accordance with biophysical chemistry. The presented description of the mechanism uses non equilibrium thermodynamics to find a simple solution for the problem.

Simultaneous current, force and dissipation measurements on the Si(111) 7×7 surface with an optimized qPlus AFM/STM technique

We present the results of simultaneous scanning-tunneling and frequency-modulated dynamic atomic force microscopy measurements with a qPlus setup. The qPlus sensor is a purely electrical sensor based on a quartz tuning fork. If both the tunneling current and the force signal are to be measured at the tip, a cross-talk of the tunneling current with the force signal can easily occur. The origin and general features of the capacitive cross-talk will be discussed in detail in this contribution. Furthermore, we describe an experimental setup that improves the level of decoupling between the tunneling-current and the deflection signal. The efficiency of this experimental setup is demonstrated through topography and site-specific force/tunneling-spectroscopy measurements on the Si(111) 7×7 surface. The results show an excellent agreement with previously reported data measured by optical interferometric deflection.

A comparison of pairs figure skaters in repeated jumps

Trends in pairs figure skating have shown that increasingly difficult jumps have become an essential aspect of high-level performance, especially in the latter part of a competitive program. We compared a repeated jump power index in a 60 s repeated jump test to determine the relationship of repeated jump test to competitive rank and to measure 2D hip, knee, and ankle angles and angular velocities at 0, 20, 40, and 60 s. Eighteen National Team Pairs Figure Skaters performed a 60 s repeated jump test on a large switch-mat with timing of flight and ground durations and digital video recording. Each 60-s period was divided into 6, 10-s intervals, with power indexes (W/kg) calculated for each 10-s interval. Power index by 10-s interval repeated measures ANOVAs (RMANOVA) showed that males exceeded females at all intervals, and the highest power index interval was during 10 to 20 s for both sexes. RMANOVAs of angles and angular velocities showed main effects for time only. Power index and jumping techniques among figure skaters showed rapid and steady declines over the test duration. Power index can predict approximately 50% of competitive rank variance, and sex differences in jumping technique were rare. Key pointsThe repeated jumps test can account for about 50% of the variance in pairs ranks.Changes in technique are largely due to fatigue, but the athletes were able to maintain a maximum flexion knee angle very close to the desired 90 degrees. Changes in angular velocity and jump heights occurred as expected, again probably due to fatigue.As expected from metabolic information, the athletes' power indexes peak around 20s and decline thereafter. Coaches should be aware of this time as a boundary beyond which fatigue becomes more manifest, and use careful choreographic choices to provide rest periods that are disguised as less demanding skating elements to afford recovery.The repeated jumps test may be a helpful off-ice test of power-endurance for figure skaters.

Near-Optimal Foraging in the Pacific Cicada Killer Sphecius convallis Patton (Hymenoptera: Crabronidae)

This study evaluated foraging effectiveness of Pacific cicada killers (Sphecius convallis) by comparing observed prey loads to that predicted by an optimality model. Female S. convallis preyed exclusively on the cicada Tibicen parallelus, resulting in a mean loaded flight muscle ratio (FMR) of 0.187 (N = 46). This value lies just above the marginal level, and only seven wasps (15%) were below 0.179. The low standard error (0.002) suggests that S. convallis is the most ideal flying predator so far examined in this respect. Preying on a single species may have allowed stabilizing selection to adjust the morphology of females to a nearly ideal size. That the loaded FMR is slightly above the marginal level may provide a small safety factor for wasps that do not have optimal thorax temperatures or that have to contend with attempted prey theft. Operational FMR was directly related to wasp body mass. Smaller wasps were overloaded in spite of provisioning with smaller cicadas, while larger wasps were underloaded despite provisioning with larger cicadas. Small wasps may have abandoned larger cicadas because of difficulty with carriage.

Diabetes is associated with impairment of uterine contractility and high Caesarean section rate

AIMS/HYPOTHESIS

The prevalence of births worldwide complicated by diabetes mellitus is increasing. In the UK, for example, <25% of diabetic women have a non-instrumental vaginal delivery. Strikingly, more than half the Caesarean sections (CS) in these patients are non-elective, but the reasons for this are not understood. We have tested the hypothesis that poor myometrial contractility as a consequence of the disease contributes to this high CS rate.

METHODS

We compared spontaneous, high K depolarisation and oxytocin-induced contractions from diabetic and matched control patients having an elective CS. To investigate the mechanism of any differences we measured intracellular Ca, and performed western blotting and compared the tissues histologically.

RESULTS

There was significantly decreased contraction amplitude and duration in uteri from diabetic compared with control patients, even when possible confounders such as BMI were analysed. Reduced intracellular calcium signals and expression of calcium entry channels were found in uteruses from diabetic patients, which, along with a reduction in muscle content found on histological examination, could explain the reduced force. Myometrium from diabetic patients was responsive to oxytocin, but still did not reach the levels found in non-diabetic patients.

CONCLUSIONS/INTERPRETATIONS

These are the first data investigating myometrium in diabetic patients and they support the hypothesis that there is poorer contractility even in the presence of oxytocin. The underlying mechanism is related to reduced Ca channel expression and intracellular calcium signals and a decrease in muscle mass. We conclude that these factors significantly contribute to the increased emergency CS rate in diabetic patients.

Wavelet cross-correlation and phase analysis of a free cantilever subjected to band excitation

This work introduces the concept of time-frequency map of the phase difference between the cantilever response signal and the driving signal, calculated with a wavelet cross-correlation technique. The wavelet cross-correlation quantifies the common power and the relative phase between the response of the cantilever and the exciting driver, yielding "instantaneous" information on the driver-response phase delay as a function of frequency. These concepts are introduced through the calculation of the response of a free cantilever subjected to continuous and impulsive excitation over a frequency band.

The interaction of Ca2+ with sarcomeric proteins: role in function and dysfunction of the heart

The hallmarks of the normal heartbeat are both rapid onset of contraction and rapid relaxation as well as an inotropic response to both increased end-diastolic volume and increased heart rate. At the microscopic level, Ca(2+) plays a crucial role in normal cardiac contraction. This paper reviews the cycle of Ca(2+) fluxes during the normal heartbeat, which underlie the coupling between excitation and contraction and permit a highly synchronized action of cardiac sarcomeres. Length dependence of the response of the regulatory sarcomeric proteins mediates the Frank-Starling Law of the heart. However, Ca(2+) transport may go astray in heart disease such as in congestive heart failure, and both jeopardize systole and diastole and triggering arrhythmias. The interaction between weak and strong segments in nonuniform cardiac muscle allows partial preservation of force of contraction but may further lead to mechanoelectric feedback or reverse excitation-contraction coupling mediating an early diastolic Ca(2+) transient caused by the rapid force decrease during the relaxation phase. These rapid force changes in nonuniform muscle may cause arrhythmogenic Ca(2+) waves to propagate by the activation of neighboring sarcoplasmic reticulum by diffusing Ca(2+) ions.

Relationships between vertical jump strength metrics and 5 meters sprint time

The aim of this study was to examine the relationship between short sprint time (5 m) and strength metrics of the countermovement jump (CMJ) using a linear transducer in a group of trained athletes. Twenty-five male, trained subjects volunteered to participate in the study. Each volunteer performed 3 maximal CMJ trials on a Smith machine. Peak instantaneous power was calculated by the product of velocity taken with the linear transducer. For sprint testing, each subject performed three maximum 5 m sprints. Only the best attempt was considered in both tests. Pearson product–moment correlation coefficients between 5 m sprint performance and strength metrics of the CMJ were generally positive and of clear moderate to strong magnitude (r = −0.664 to −0.801). More noticeable was the significant predictive value of bar displacement time (r= ∼0.70) to sprint performance. Nevertheless, a non-significant predictive value of peak bar velocity and rate of force development measurements was found. These results underline the important relationship between 5 m sprint and maximal lower body strength, as assessed by the force, power and bar velocity displacement. It is suggested that sprinting time performance would benefit from training regimens aimed to improve these performance qualities.

Detailed study of amplitude nonlinearity in piezoresistive force sensors

This article upgrades the RC linear model presented for piezoresistive force sensors. Amplitude nonlinearity is found in sensor conductance, and a characteristic equation is formulated for modeling its response under DC-driving voltages below 1 V. The feasibility of such equation is tested on four FlexiForce model A201-100 piezoresistive sensors by varying the sourcing voltage and the applied forces. Since the characteristic equation proves to be valid, a method is presented for obtaining a specific sensitivity in sensor response by calculating the appropriate sourcing voltage and feedback resistor in the driving circuit; this provides plug-and-play capabilities to the device and reduces the start-up time of new applications where piezoresistive devices are to be used. Finally, a method for bypassing the amplitude nonlinearity is presented with the aim of reading sensor capacitance.

Preliminary development of the Active Colonoscopy Training Model

Formal colonoscopy training requires a significant amount of time and effort. In particular, it requires actual patients for a realistic learning experience. The quality of colonoscopy training varies, and includes didactic courses and procedures proctored by skilled surgeons. A colonoscopy training model is occasionally used as part of the training method, but the effects are minute due to both the simple and tedious training procedures. To enhance the educational effect of the colonoscopy training model, the Active Colonoscopy Training Model (ACTM) has been developed. ACTM is an interactive colonoscopy training device which can create the environment of a real colonoscopy procedure as closely as possible. It comprises a configurable rubber colon, a human torso, sensors, a display, and the control part. The ACTM provides audio and visual interaction to the trainee by monitoring important factors, such as forces caused by the distal tip and the shaft of the colonoscope and the pressure to open up the lumen and the localization of the distal tip. On the computer screen, the trainee can easily monitor the status of the colonoscopy, which includes the localization of the distal tip, maximum forces, pressure inside the colon, and surgery time. The forces between the rubber colon and the constraints inside the ACTM are measured and the real time display shows the results to the trainee. The pressure sensors will check the pressure at different parts of the colon. The real-time localized distal tip gives the colonoscopy trainee easier and more confident operation without introducing an additional device in the colonoscope. With the current need for colonoscopists and physicians, the ACTM can play an essential role resolving the problems of the current colonoscopy training model, and significantly improve the training quality of the colonoscopy.

Probing forces of menisci: what levels are safe for arthroscopic surgery

PURPOSE

to facilitate effective learning, feedback on performance during arthroscopic training is essential. Less attention has been paid to feedback on monitoring safe handling of delicate tissues such as meniscus. The goal is to measure in vitro probing forces of menisci and compare them with a theoretical maximum probing force (TMPF).

METHOD

menisci samples of ten cadavers were mounted on force platforms to measure probing forces up to 20 N in three directions. Nineteen subjects participated: six novices (experience <60 arthroscopies), ten intermediates (>60 arthroscopies), and three faculty (>250 a year). All had to perform three tasks on each meniscus sample with an arthroscopic probe: push three times on the superior meniscal surface, perform one continuous run on the superior meniscal surface, and push three times on the inferior meniscal surface. The absolute maximum probing force (AMPF) was determined for each condition. A multivariable linear regression analysis was performed to assess the influence of experience on the force magnitude (P < 0.05). AMPFs were compared to the TMPF (estimated to be 8.5 N).

RESULTS

the AMPF of the push task was on average 2.8 N (standard deviation (SD) of 0.8 N), of the continuous run task 2.5 N (SD 0.9 N), and of the pull task 3.9 N (SD 2.0 N). Significant difference was present between experts and novices (P < 0.05). The AMPFs are in the same order of magnitude as the TMPF.

CONCLUSION

the results indicate the necessity of using a safety level for tissue manipulation when training arthroscopy and a value for is magnitude.

Tip-sample interactions on graphite studied using the wavelet transform

Wavelet transform analysis is applied to a thermally excited cantilever to get insights into fundamental thermodynamical properties of its motion. The shortcomings of the widely used Fourier analysis are briefly discussed to put into perspective the wavelet transform analysis, used to describe the temporal evolution of the spectral content of the thermal oscillations of a cantilever with an interacting tip. This analysis allows to retrieve the force gradients, the forces and the Hamaker constant in a measurement time of less than 40 ms.

Effects of differing response-force requirements on food-maintained responding in C57Bl/6J mice

The effect of force requirements on response effort was examined using inbred C57BL/6J mice trained to press a disk with their snout. Lateral peak forces greater than 2 g were defined as responses (i.e., all responses above the measurement threshold). Different, higher force requirements were used to define criterion responses (a subclass of all responses) that exceeded the requirement and produced a reinforcer. The reinforcer was sweetened, condensed milk, delivered upon response termination. All mice were exposed to two ascending series of criterion force requirements (2, 4, 8, 16, and 32 g). Increasing the force requirement initially decreased criterion response rates, but criterion response rates recovered with continued exposure, except at the 32-g requirement. Response rates for all measured responses initially increased with increasing force requirements, but then decreased with continued exposure. The second exposure series produced more stable response rate changes than the first series. The time-integral of force (area under the force-time curve for individual responses, which is proportional to energy expenditure for each response) increased with the increase in the force requirement. The C57BL/6J inbred strain generated average force output similar to CD-1 outbred stock mice trained on the same force requirements. C57BL/6J inbred strain mice differed from CD-1 mice in initial response rates (for all responses above threshold) and had lower response rates at the 16 and 32 g requirements resulting in lower total force output. These data show for both mice types that increased force requirements resulted in increased overall responding (all measured responses), which contradicts a punishment interpretation of criterion response decrements. C57BL\6 inbred mice showed individual differences comparable to the outbred CD-1 stock. C57BL/6 mice did not maintain responding as well at the higher force requirements, which may be due to their small body size and weight, compared to the larger and heavier CD-1 mice.

Illusory force perception following a voluntary limb movement

We present a novel illusion in which participants report constant forces on their hand as steadily increasing. Participants made discrete reaching movements perturbed by a lateral force that increased with the distance moved; when stationary at the end of the movement, a true constant force was perceived to increase. We tested perceived subjective equality by increasing or decreasing the force. The illusion was significantly stronger when the perturbation was applied during active movement. We conclude that the unusual context of moving against lateral spring forces results in participants failing to predict steady lateral forces at the end of their movement, and causes an illusion of increasing forces even after movement termination. This result further emphasizes the role of action prediction in sensory perception.

The perpetual movements of anaphase

One of the most extraordinary events in the lifetime of a cell is the coordinated separation of sister chromatids during cell division. This is truly the essence of the entire mitotic process and the reason for the most profound morphological changes in cytoskeleton and nuclear organization that a cell may ever experience. It all occurs within a very short time window known as "anaphase", as if the cell had spent the rest of its existence getting ready for this moment in an ultimate act of survival. And there is a good reason for this: no space for mistakes. Problems in the distribution of chromosomes during cell division have been correlated with aneuploidy, a common feature observed in cancers and several birth defects, and the main cause of spontaneous abortion in humans. In this paper, we critically review the mechanisms of anaphase chromosome motion that resisted the scrutiny of more than 100 years of research, as part of a tribute to the pioneering work of Miguel Mota.