Compressive Stimuli Research Articles

Granular metamaterials with dynamic bond reconfiguration.

Biological materials dynamically reconfigure their underlying structures in response to stimuli, achieving adaptability and multifunctionality. Conversely, mechanical metamaterials have fixed interunit connections that restrict adaptability and reconfiguration. This study introduces granular metamaterials composed of discrete bimaterial structured particles that transition between assembled and unassembled states through mechanical compression and thermal stimuli. These materials enable dynamic bond reconfiguration, allowing reversible bond breaking and formation, similar to natural systems. Leveraging their discrete nature, these materials can adaptively reconfigure their shape and respond dynamically to varying conditions. Our investigations reveal that these granular metamaterials can substantially alter their mechanical properties, like compression, shearing, and bending, offering tunable mechanical characteristics across different states. Furthermore, they exhibit collective behaviors like directional movement, object capture, transportation, and gap crossing, showcasing their potential for reprogrammable functionalities. This work highlights the dynamic reconfigurability and robust adaptability of granular metamaterials, expanding their potential in responsive architecture and autonomous robotics.

Biomorph Soft Actuators with Tardigrade‐Like Resilience

AbstractTardigrades are the most resilient biospecies on Earth, capable of surviving extreme conditions including high temperatures, pressures, air deprivation, and exposure to noxious chemicals and radiation. The study here undertakes biomimicry of the remarkable adaptability of tardigrades by designing biomorph soft actuators (BSAs) that can endure these harsh environments. Unlike previous tardigrade‐inspired materials, which lacked a naturalistic interaction with their surroundings, the BSAs replicate the anatomical macrostructures and the non‐monotonic environmental resilience of tardigrades, especially their ability to adapt via dehydration and rehydration. Dual‐layer hydrogel spheres are employed with embedded fluid bubbles, creating cohesive yet non‐monolithic smart BSA structures. These structures exhibit high resilience to compressive, thermal, and radiation stimuli, achieved through thermoresponsive shape morphing driven by fluid balance. Their advanced capabilities are also demonstrated, such as driving a McKibben‐type artificial muscle and rapidly regenerating themselves from a state exposed to hazardous chemicals. Such versatile actuating biomorphs hold great promise for various autonomous applications, including soft robotic operations in aqueous effluents, deserts, polar regions, and outer space.

Magnetically Actuated Transport Pipeline with Self-Perception

Soft transportation devices with high flexibility, good stability, and quick controllability have attracted increasing attention. However, a smart soft transportation device with tactile perception and a non-contact actuating mode remains a challenge. This work reports a magnetic soft pipeline (MSP) composed of sensor film, a magnetorheological elastomer (MRE) cavity pipeline, and heater film, which can not only respond well to tactile compression stimuli but also be transported by magnetic actuation. Notably, the sensor film was integrated on the upper surface of an MRE pipeline, and the relative resistance change (∆R/R0) of the MSP was maintained at 55.8% under 2.2 mm compression displacement during 4000 loading cycles. Moreover, the heater film was integrated on the lower surface of the MRE pipeline, which endows the MSP with an electrothermal heating characteristic. The temperature of the MSP can be increased from 26.7 °C to 38.1 °C within 1 min under 0.6 V. Furthermore, the MSP was attracted and deformed under the magnetic field, and the ∆R/R0 of the MSP reached 69.1% under application of a 165 mT magnetic field density. Benefiting from the excellent perception and magnetic deformation performances, the magnetic actuate transportation of the MSP with self-sensing was successfully achieved. This multi-functional soft pipeline integrated with in situ self-sensing, electrothermal heating, and non-contact magnetic actuating transportation performance possess high potential in smart flexible electronic devices.

Changes in the Concentration of fat, Protein and Carbohydrates During the Excretion of Milk by Vacuum Breast Pump and Breast Pump with Compression

Background: The purpose of the work is to investigate the contents of the main nutrients of milk (fat, protein, lactose), as well as the energy value of milk in the process of expression milk using an vacuum electric breast pump and vacuum electric breast pump with compression pulses simultaneously. Method: Surveys were conducted on 9 women 5-8 weeks of lactation. The analysis was carried out in 10 ml samples of milk, which were continuously expression with breast pump «Laktopuls»: only with vacuum stimuli, and simultaneously with vacuum and compression stimuli. The sampling continuity was ensured by a specially developed procedure. Milk analysis in the samples was performed 1-1.5 hours after gland expression on a Miris AB Uppsala, Sweden, human milk analyzer. Finding: The largest changes in milk samples were observed in fat concentration. The fat content in milk increased in each subsequent sample and in the latter samples could exceed its content in the initial samples by 3-4 times. The total amount of fat was about 25% more when milk ejected by breast pump with vacuum and compression stimuli than with vacuum stimulus only. When determining the protein concentration in milk samples, an increase in its concentration was also found during milk ejection, but on 10-20%. In contrast to the dynamics of fat and protein concentrations, the carbohydrate concentration did not change in all women during the milk ejection. Conclusion: A method has been developed that allows analyzing milk nutrients during the continuous removal of milk from the gland. Surveys have shown that ejection of milk with breast pump with vacuum and compression stimuli, increases the amount of fat and protein in breast milk.

Novel Chip for Applying Mechanical Forces on Human Skin Models Under Dynamic Culture Conditions.

In recent years the need for in vitro skin models as a replacement for animal studies has resulted in significant progress in the development of skin-on-a-chip models. These devices allow the fine control of the microenvironment of the model and the incorporation of chemical and physical stimuli. In this study, we describe the development of an easy and low-budget open-top dynamic microfluidic device for skin-on-a-chip experiments using polydimethylsiloxane and a porous polyethylene terephthalate membrane. The chip allows the incorporation of compressive stimuli during the cultivation period by the use of syringe pumps. Proof-of-concept results show the successful differentiation of the cells and establishment of the skin structure in the chip. The microfluidic skin-on-a-chip models presented in this study can serve as a platform for future drug and feasibility studies.

Functional magnetic alginate/gelatin sponge-based flexible sensor with multi-mode response and discrimination detection properties for human motion monitoring

The functional flexible sensors that can simultaneously detect multiple external excitations have exhibited great potential in the human-machine interaction and wearable electronics. However, it is still a primary challenge to develop a multi-mode sensor that can achieve sensitivity equilibrium towards different stimuli, and effectively recognize external stimulus while in a facile and cost-effective material and methodology. This study presented a functional flexible sensor based on natural polymer sodium alginate and gelatin sponge electrode which could detect both external mechanical and magnetic stimuli with superiorities of outstanding sensing capability and stability. With the optimal multilayered structure, it possessed high magnetic responsive sensitivity of 0.45 T−1, excellent stability and recoverability. Its electrical property variations also displayed high sensitivity and durability under cyclic stretching, bending and compressing stimuli for 1000 cycles. More importantly, the sensor could not only respond to magnetic field and compression stimuli with contrary electrical responses, but also recognize the respective input signals to decouple different stimuli in real time. Furthermore, it was developed as electronic skins and smart sensor arrays for human physiological signals and mechanical-magnetic detection. Based on excellent multifunctional response characteristics, the sensor showed significant potential in next-generation intelligent multifunctional electronic system and artificial intelligence.

Difference in the Osteoblastic Calcium Signaling Response Between Compression and Stretching Mechanical Stimuli

In orthodontics, various forms of mechanical stimulation induce opposing bone metabolism mechanisms. Bone resorption and bone formation occur in areas of compressive and tensile force action, respectively. The mechanism that causes such a difference in bone metabolism is still unclear. In this study, we investigated the difference in the osteoblastic calcium signaling response between compression and stretching mechanical stimuli. We applied two types of mechanical stimuli to osteoblast-like MC3T3-E1 cells: first microneedle direct indentation onto the cell as compression stimuli, and second stretching stimuli by using originally developed cell stretching MEMS device. Cells were treated with thapsigargin and calcium-free medium to investigate the source of the calcium ion. The results demonstrated variations in the osteoblastic calcium signaling response between the compression and stretching stimuli. The magnitude of an increase in the intracellular calcium ion concentration is much higher in the compression stimuli-applied cell group. Treatment of calcium-free medium nearly suppressed the calcium signaling response to both types of mechanical stimulation. Thapsigargin treatment induced an increase in the magnitude of calcium signaling response to the compression stimuli, while suppressed the slow and sustained increase in the calcium ion concentration in the stretching stimuli-applied cell group. These findings demonstrate the difference in the characteristics of osteoblastic calcium signaling response between compression and stretching mechanical stimuli.

Mechanosensitive enteric neurons in the guinea pig gastric fundus and antrum.

Coping with the ingested food, the gastric regions of fundus, corpus, and antrum display different motility patterns. Intrinsic components of such patterns involving mechanosensitive enteric neurons (MEN) have been described in the guinea pig gastric corpus but are poorly understood in the fundus and antrum. To elucidate mechanosensitive properties of myenteric neurons in the gastric fundus and antrum, membrane potential imaging using Di-8-ANEPPS was applied. A small-volume injection led to neuronal compression. We analyzed the number of MEN and their firing frequency in addition to the involvement of selected mechanoreceptors. To characterize the neurochemical phenotype of MEN, we performed immunohistochemistry. In the gastric fundus, 16% of the neurons reproducibly responded to mechanical stimulation and thus were MEN. Of those, 83% were cholinergic and 19% nitrergic. In the antrum, 6% of the neurons responded to the compression stimulus, equally distributed among cholinergic and nitrergic MEN. Defunctionalizing the sensory extrinsic afferents led to a significant drop in the number of MEN in both regions. We provided evidence for MEN in the gastric fundus and antrum and further investigated mechanoreceptors. However, the proportions of the chemical phenotypes of the MEN differed significantly between both regions. Further investigations of synaptic connections of MEN are crucial to understand the hardwired neuronal circuits in the stomach.

Pulse Wave Velocity is affected by the magnitude of the Pulse Wave, in human veins

ObjectivesPulse Wave Velocity (PWV) is theoretically affected by the magnitude of the PW (PWm), in veins as well as in arteries, but, to our knowledge, this possibility has never been tested experimentally. Aim of this work is to investigate the dependence of PWV on PWm. The issue is investigated in limb veins, whereby PWs of different magnitude can be generated by controlled pneumatic compressions of the limb extremity. MethodsVenous PWV (vPWV) was measured using Doppler-US on the upper limb of 13 healthy volunteers in supine position, after 15 min of rest, using three different compression levels (100, 200, 300 mmHg of 1-s duration) in a randomized order. Eight compressions were delivered 15-s apart for each of the three levels. The peak frequency of the Doppler shift was used as an indication of PWm. ResultsThe compression level had a statistically significant effect on both vPWV and PWm (p < 0.001), but the effect was reduced for those subjects exhibiting, at the lowest compression intensity, an already elevated vPWV value (exponential fitting, R2 = 0.66). ConclusionThe magnitude of the exogenously generated venous PWs significantly affected vPWV, suggesting that the delivery of the compressive stimulus should be carefully implemented and monitored. Further studies are needed to investigate the implications in arterial PWV assessment.

Piezoresistivity modeling of soft tissue electrical-mechanical properties: A validation study.

In general, the electrical property of soft tissues is sensitive to the force applied to their surface. To further study the relationship between the force and the electrical property of soft tissues, this paper attempts to investigate the effect of static and higher-order stresses on electrical properties. Overall, a practical experimental platform is designed to acquire the force information and the electrical property of soft tissues during a contact procedure, which is featured different compression stimuli, such as constant pressing force, constant pressing speed, and step-force compression, etc. Furthermore, the piezoresistive characteristic is innovatively introduced to model the mechanical-electrical properties of soft tissue. Finite Element Modeling (FEM) is adopted to fit the static piezoresistivity of the soft tissue. Finally, experimental studies were performed to demonstrate the effect of stress on the electrical properties and the feasibility of the proposed piezoresistive model to describe soft tissues' mechanical and electrical properties.

Efficacy of Laryngeal Mask Airway Impregnation with Diltiazem Gel on Hemodynamic Changes in Patients with Hypertension Undergoing Phacoemulsification Surgery: A Randomized Clinical Trial

Background: Airway control problems are among the most prevalent causes of anesthesia-related mortality and morbidity. Some devices provide patients with adequate oxygen supply and ventilation during surgery by creating a safe airway in anesthetized patients. One of these devices is the laryngeal mask airway (LMA). The compression and painful stimuli following the LMA cuff inflation can lead to hemodynamic changes. Diltiazem gel is used in the control and treatment of hypertension (HTN) and heart arrhythmia and is absorbed through the tracheal mucosa. Objectives: By assuming that diltiazem gel is superior to other drugs used to prevent arrhythmias and hemodynamic changes during surgery, this study aimed to evaluate the effect of LMA impregnation with diltiazem gel, compared to lubricant gel. Methods: This study was conducted as a double-blind, randomized clinical trial on 80 participants with HTN who were candidates for phacoemulsification (phaco) surgery in Imam Khomeini Hospital, Kermanshah, Iran. The participants were assigned to an intervention (LMA impregnated with diltiazem gel) and a control group (LMA impregnated with lubricant gel) through the block random method in the form of 40 blocks of 2 using a random-numbers table. Hemodynamic changes (systolic and diastolic blood pressure and heart rate) were measured before, immediately after, 5 min, and 15 min after intubation, during surgery every 15 min, upon entering the recovery unit, and 15 and 30 min after entering the recovery unit. Results: The mean systolic and diastolic blood pressure in the intervention group showed a significant decrease, compared to that in the control group. A significant difference was also observed in the mean heart rate difference between the two study groups, but only at the beginning of the study (P&lt;0.05). Additionally, according to the results of repeated measures analysis of variance, the mean of the measured variables showed a significant difference at different measurement times in the intervention group (P&lt;0.05). Conclusion: The findings supported the effectiveness of diltiazem gel in reducing blood pressure, especially in the final stages of surgery, decreasing the number of premature ventricular contractions, and controlling normal breathing. Therefore, specialists and surgeons can use diltiazem gel to control the hemodynamic status of patients.

Quantitative Ultrasound Techniques Used for Peripheral Nerve Assessment.

This review article describes quantitative ultrasound (QUS) techniques and summarizes their strengths and limitations when applied to peripheral nerves. A systematic review was conducted on publications after 1990 in Google Scholar, Scopus, and PubMed databases. The search terms "peripheral nerve", "quantitative ultrasound", and "elastography ultrasound" were used to identify studies related to this investigation. Based on this literature review, QUS investigations performed on peripheral nerves can be categorized into three main groups: (1) B-mode echogenicity measurements, which are affected by a variety of post-processing algorithms applied during image formation and in subsequent B-mode images; (2) ultrasound (US) elastography, which examines tissue stiffness or elasticity through modalities such as strain ultrasonography or shear wave elastography (SWE). With strain ultrasonography, induced tissue strain, caused by internal or external compression stimuli that distort the tissue, is measured by tracking detectable speckles in the B-mode images. In SWE, the propagation speed of shear waves, generated by externally applied mechanical vibrations or internal US "push pulse" stimuli, is measured to estimate tissue elasticity; (3) the characterization of raw backscattered ultrasound radiofrequency (RF) signals, which provide fundamental ultrasonic tissue parameters, such as the acoustic attenuation and backscattered coefficients, that reflect tissue composition and microstructural properties. QUS techniques allow the objective evaluation of peripheral nerves and reduce operator- or system-associated biases that can influence qualitative B-mode imaging. The application of QUS techniques to peripheral nerves, including their strengths and limitations, were described and discussed in this review to enhance clinical translation.

Mechanical Janus Structures by Soft–Hard Material Integration (Adv. Mater. 6/2023)

Superstructure Engineering In article number 2208339, Baoxing Xu and co-workers present a mechanical Janus structure by leveraging a soft–hard material integration and report its unique rotation under mechanical compression stimuli. This rotation behavior offers a facile route for the assembled superstructures with programmable, local organizations, capable of regulating and filtering acoustic wave propagations in applications.

3D Printable One‐Part Carbon Nanotube‐Elastomer Ink for Health Monitoring Applications

Abstract3D printing of conductive elastomers is a promising route to personalized health monitoring applications due to its flexibility and biocompatibility. Here, a one‐part, highly conductive, flexible, stretchable, 3D printable carbon nanotube (CNT)‐silicone composite is developed and thoroughly characterized. The one‐part nature of the inks: i) enables printing without prior mixing and cures under ambient conditions; ii) allows direct dispensing at ≈100 µm resolution printability on nonpolar and polar substrates; iii) forms both self‐supporting and high‐aspect‐ratio structures, key aspects in additive biomanufacturing that eliminate the need for sacrificial layers; and iv) lends efficient, reproducible, and highly sensitive responses to various tensile and compressive stimuli. The high electrical and thermal conductivity of the CNT‐silicone composite is further extended to facilitate use as a flexible and stretchable heating element, with applications in body temperature regulation, water distillation, and dual temperature sensing and Joule heating. Overall, the facile fabrication of this composite points to excellent synergy with direct ink writing and can be used to prepare patient‐specific wearable electronics for motion detection and cardiac and respiratory monitoring devices and toward advanced personal health tracking and bionic skin applications.

Effects of different intermittent pneumatic compression stimuli on ankle dorsiflexion range of motion.

Despite substantial evidence of the effectiveness of intermittent pneumatic compression (IPC) treatments for range of motion (ROM) improvement, little evidence is available regarding how different IPC stimuli affect ankle dorsiflexion (DF) ROM. This study aimed to investigate the effects of different IPC stimuli on the ankle DF ROM. Fourteen, university intermittent team sport male athletes (age: 21 ± 1 year, height: 1.74 ± 0.05 m, body mass: 70.9 ± 7.7 kg, body fat percentage: 14.2 ± 3.6%, body mass index: 23.5 ± 2.5kg/m2; mean ± standard deviation) completed four experimental trials in a random order: 1) no compression with wearing IPC devices (SHAM), 2) the sequential compression at approximately 80mmHg (SQUEE80), 3) the uniform compression at approximately 80mmHg (BOOST80), and 4) the uniform compression at approximately 135mmHg (BOOST135). For the experimental trials, the participants were initially at rest for 10min and then assigned to either a 30-min SHAM, SQUEE80, BOOST80, or BOOST135. Participants rested for 20min after IPC treatment. The Weight-Bearing Lunge Test (WBLT), popliteal artery blood flow, pressure-to-pain threshold (PPT), muscle hardness, heart rate variability, and perceived relaxation were measured before (Pre) and immediately after IPC treatment (Post-0) and 20min after IPC treatment (Post-20), and the changes in all variables from Pre (Δ) were calculated. ΔWBLT performance, ΔPPT, and Δperceived relaxation in all IPC treatments were significantly higher than those in SHAM at Post-0 and Post-20 (p < 0.05). ΔPopliteal artery blood flow in BOOST80 and BOOST135 was significantly higher than that in SHAM and SQUEE80 at Post-0 (p < 0.05). ΔMuscle hardness and Δheart rate variability did not differ significantly between trials. In conclusion, IPC treatments, irrespective of applied pressure and mode of compression, increased ankle DF ROM. This resulted from decreased pain sensitivity (i.e., increased PPT). In addition, high inflation pressure and frequency did not provide additional benefits in increasing ankle DF ROM.

Optimizing artificial meniscus by mechanical stimulation of the chondrocyte-laden acellular meniscus using ad hoc bioreactor

BackgroundTissue engineering focuses on reconstructing the damaged meniscus by mimicking the native meniscus. The application of mechanical loading on chondrocyte-laden decellularized whole meniscus is providing the natural microenvironment. The goal of this study was to evaluate the effects of dynamic compression and shear load on chondrocyte-laden decellularized meniscus.Material and methodsThe fresh samples of rabbit menisci were decellularized, and the DNA removal was confirmed by histological assessments and DNA quantification. The biocompatibility, degradation and hydration rate of decellularized menisci were evaluated. The decellularized meniscus was injected at a density of 1 × 105 chondrocyte per scaffold and was subjected to 3 cycles of dynamic compression and shear stimuli (1 h of 5% strain, ± 25°shear at 1 Hz followed by 1 h rest) every other day for 2 weeks using an ad hoc bioreactor. Cytotoxicity, GAG content, ultrastructure, gene expression and mechanical properties were examined in dynamic and static condition and compared to decellularized and intact menisci.ResultsMechanical stimulation supported cell viability and increased glycosaminoglycan (GAG) accumulation. The expression of collagen-I (COL-I, 10.7-folds), COL-II (6.4-folds), aggrecan (AGG, 3.2-folds), and matrix metalloproteinase (MMP3, 2.3-folds) was upregulated compared to the static conditions. Furthermore, more aligned fibers and enhanced tensile strength were observed in the meniscus treated in dynamic condition with no sign of mineralization.ConclusionCompress and shear stimulation mimics the loads on the joint during walking and be able to improve cell function and ultrastructure of engineered tissue to recreate a functional artificial meniscus.

Location-Dependent Human Osteoarthritis Cartilage Response to Realistic Cyclic Loading: Ex-Vivo Analysis on Different Knee Compartments.

Objective: Osteoarthritis (OA) is a multifactorial musculoskeletal disorder affecting mostly weight-bearing joints. Chondrocyte response to load is modulated by inflammatory mediators and factors involved in extracellular cartilage matrix (ECM) maintenance, but regulatory mechanisms are not fully clarified yet. By using a recently proposed experimental model combining biomechanical data with cartilage molecular information, basally and following ex-vivo load application, we aimed at improving the understanding of human cartilage response to cyclic mechanical compressive stimuli by including cartilage original anatomical position and OA degree as independent factors. Methods: 19 mono-compartmental Knee OA patients undergoing total knee replacement were recruited. Cartilage explants from four different femoral condyles zones and with different degeneration levels were collected. The response of cartilage samples, pooled according to OA score and anatomical position was tested ex-vivo in a bioreactor. Mechanical stimulation was obtained via a 3-MPa 1-Hz sinusoidal compressive load for 45-min to replicate average knee loading during normal walking. Samples were analysed for chondrocyte gene expression and ECM factor release. Results: Non parametric univariate and multivariate (generalized linear mixed model) analysis was performed to evaluate the effect of compression and IL-1β stimulation in relationship to the anatomical position, local disease severity and clinical parameters with a level of significance set at 0.05. We observed an anti-inflammatory effect of compression inducing a significant downmodulation of IL-6 and IL-8 levels correlated to the anatomical regions, but not to OA score. Moreover, ADAMTS5, PIICP, COMP and CS were upregulated by compression, whereas COL-2CAV was downmodulated, all in relationship to the anatomical position and to the OA degree. Conclusion: While unconfined compression testing may not be fully representative of the in-vivo biomechanical situation, this study demonstrates the importance to consider the original cartilage anatomical position for a reliable biomolecular analysis of knee OA metabolism following mechanical stimulation.

Quantitative reorientation behaviors of macro‐twin interfaces in shape‐memory alloy under compression stimulus in situ TEM

Twinning stress is known to be a critical factor for the actuating performance of magnetic shape memory alloys because of the harmful deterioration of their magnetic field-induced strain effect. However, the intrinsic origin of the high twinning stress is still in debate. In this work, we firstly fill this gap by precisely probing the reorientation behaviors of A-C and A-B two common macro-twin interfaces under the stimulus of uniaxial compression in-situ transmission electron microscope. The grain boundary is proved to be the main reason for large twinning stress. The twinning stress of the A-C and A-B type interfaces quantitatively are ∼0.69 and 1.27 MPa within the plate respectively. The A-C type interface evidently has smaller twinning stress and larger deformation variable than the A-B interface. Under the action of compression, not only the orientations of the crystals have changed, but also the roles of the major and minor lamellae have changed for both interfaces due to the movements of twinning dislocations. Combining in-situ and quasi in-situ electron diffraction data, the reorientation process is clearly and intuitively shown by the stereographic projection. Atomic models and the theory of dislocation motion are proposed to phenomenologically clarify the intrinsic mechanism. This work is believed to not only provide a deeper understanding of the deformation mechanism of magnetic shape memory alloys under uniaxial compression testing, but also discover that compression training is not the mechanical training way to decrease the twinning stress of non-modulated martensite in single crystal shape memory alloys.

Linear vector models of time perception account for saccade and stimulus novelty interactions

Various models (e.g., scalar, state-dependent network, and vector models) have been proposed to explain the global aspects of time perception, but they have not been tested against specific visual phenomena like perisaccadic time compression and novel stimulus time dilation. Here, in two separate experiments (N = 31), we tested how the perceived duration of a novel stimulus is influenced by 1) a simultaneous saccade, in combination with 2) a prior series of repeated stimuli in human participants. This yielded a novel behavioral interaction: pre-saccadic stimulus repetition neutralizes perisaccadic time compression. We then tested these results against simulations of the above models. Our data yielded low correlations against scalar model simulations, high but non-specific correlations for our feedforward neural network, and correlations that were both high and specific for a vector model based on identity of objective and subjective time. These results demonstrate the power of global time perception models in explaining disparate empirical phenomena and suggest that subjective time has a similar essence to time's physical vector.

Early mechanical stimulation of the nipple-areola receptors complex promotes the mammary milk ejection function in women delivered by cesarean section

Mechanical stimulation and milk ejection from mammary gland in women delivered by caesarean section since 1 day post partum by the breastpump with vacuum and compression stimuli promotes milk ejection function. On the third day postpartum the stimulated mothers had significantly more milk flow reflex peaks than those who were not subjected to stimulation during the 10 min milk ejection session.