Apparatus for monitoring load bearing rehabilitation exercises of a transfemoral amputee fitted with an osseointegrated fixation : a proof-of-concept study

The purpose of this proof-of-concept study was to determine the relevance of direct measurements to monitor the load applied on the osseointegrated fixation of transfemoral amputees during static load bearing exercises. The objectives were (A) to introduce an apparatus using a three-dimensional load transducer, (B) to present a range of derived information relevant to clinicians, (C) to report on the outcomes of a pilot study and (D) to compare the measurements from the transducer with those from the current method using a weighing scale. One transfemoral amputee fitted with an osseointegrated implant was asked to apply 10 kg, 20 kg, 40 kg and 80 kg on the fixation, using self-monitoring with the weighing scale. The loading was directly measured with a portable kinetic system including a six-channel transducer, external interface circuitry and a laptop. As the load prescribed increased from 10 kg to 80 kg, the forces and moments applied on and around the antero-posterior axis increased by 4 fold anteriorly and 14 fold medially, respectively. The forces and moments applied on and around the medio-lateral axis increased by 9 fold laterally and 16 fold from anterior to posterior, respectively. The long axis of the fixation was overloaded and underloaded in 17 % and 83 % of the trials, respectively, by up to ±10 %. This proof-of-concept study presents an apparatus that can be used by clinicians facing the challenge of improving basic knowledge on osseointegration, for the design of equipment for load bearing exercises and for rehabilitation programs.

The effect of unlocking RGD-motifs in collagen I on pre-osteoblast adhesion and differentiation

Denaturation of extracellular matrix proteins exposes cryptic binding sites. It is hypothesized that binding of cell adhesion receptors to these cryptic binding sites regulates cellular behaviour during tissue repair and regeneration. To test this hypothesis, we quantify the adhesion of pre-osteoblastic cells to native (Col) and partially-denatured (pdCol) collagen I using single-cell force spectroscopy. During early stages of cell attachment (≤180 s) pre-osteoblasts (MC3T3-E1) adhered significantly stronger to pdCol compared to Col. RGD (Arg-Gly-Asp)-containing peptides suppressed this elevated cell adhesion. We show that the RGD-binding α5β1- and αv-integrins mediated pre-osteoblast adhesion to pdCol, but not to Col. On pdCol pre-osteoblasts had a higher focal adhesion kinase tyrosine-phosphorylation level that correlated with enhanced spreading and motility. Moreover, pre-osteoblasts cultured on pdCol showed a pronounced matrix mineralization activity. Our data suggest that partially-denatured collagen exposes RGD-motifs that trigger binding of α5β1- and αv-integrins. These integrins initiate cellular processes that stimulate osteoblast adhesion, spreading, motility and differentiation. Taken together, these quantitative insights reveal an approach for the development of alternative collagen I- based surfaces for tissue engineering applications.

Mathematical modelling of muscle recruitment and function in the lumbar spine

Low back pain is an increasing problem in industrialised countries and although it is a major socio-economic problem in terms of medical costs and lost productivity, relatively little is known about the processes underlying the development of the condition. This is in part due to the complex interactions between bone, muscle, nerves and other soft tissues of the spine, and the fact that direct observation and/or measurement of the human spine is not possible using non-invasive techniques. Biomechanical models have been used extensively to estimate the forces and moments experienced by the spine. These models provide a means of estimating the internal parameters which can not be measured directly. However, application of most of the models currently available is restricted to tasks resembling those for which the model was designed due to the simplified representation of the anatomy. The aim of this research was to develop a biomechanical model to investigate the changes in forces and moments which are induced by muscle injury. In order to accurately simulate muscle injuries a detailed quasi-static three dimensional model representing the anatomy of the lumbar spine was developed. This model includes the nine major force generating muscles of the region (erector spinae, comprising the longissimus thoracis and iliocostalis lumborum; multifidus; quadratus lumborum; latissimus dorsi; transverse abdominis; internal oblique and external oblique), as well as the thoracolumbar fascia through which the transverse abdominis and parts of the internal oblique and latissimus dorsi muscles attach to the spine. The muscles included in the model have been represented using 170 muscle fascicles each having their own force generating characteristics and lines of action. Particular attention has been paid to ensuring the muscle lines of action are anatomically realistic, particularly for muscles which have broad attachments (e.g. internal and external obliques), muscles which attach to the spine via the thoracolumbar fascia (e.g. transverse abdominis), and muscles whose paths are altered by bony constraints such as the rib cage (e.g. iliocostalis lumborum pars thoracis and parts of the longissimus thoracis pars thoracis). In this endeavour, a separate sub-model which accounts for the shape of the torso by modelling it as a series of ellipses has been developed to model the lines of action of the oblique muscles. Likewise, a separate sub-model of the thoracolumbar fascia has also been developed which accounts for the middle and posterior layers of the fascia, and ensures that the line of action of the posterior layer is related to the size and shape of the erector spinae muscle. Published muscle activation data are used to enable the model to predict the maximum forces and moments that may be generated by the muscles. These predictions are validated against published experimental studies reporting maximum isometric moments for a variety of exertions. The model performs well for fiexion, extension and lateral bend exertions, but underpredicts the axial twist moments that may be developed. This discrepancy is most likely the result of differences between the experimental methodology and the modelled task. The application of the model is illustrated using examples of muscle injuries created by surgical procedures. The three examples used represent a posterior surgical approach to the spine, an anterior approach to the spine and uni-lateral total hip replacement surgery. Although the three examples simulate different muscle injuries, all demonstrate the production of significant asymmetrical moments and/or reduced joint compression following surgical intervention. This result has implications for patient rehabilitation and the potential for further injury to the spine. The development and application of the model has highlighted a number of areas where current knowledge is deficient. These include muscle activation levels for tasks in postures other than upright standing, changes in spinal kinematics following surgical procedures such as spinal fusion or fixation, and a general lack of understanding of how the body adjusts to muscle injuries with respect to muscle activation patterns and levels, rate of recovery from temporary injuries and compensatory actions by other muscles. Thus the comprehensive and innovative anatomical model which has been developed not only provides a tool to predict the forces and moments experienced by the intervertebral joints of the spine, but also highlights areas where further clinical research is required.

Thin film deposition and characterization of pure and iron-doped electron-beam evaporated tungsten oxide for gas sensors

Pure Tungsten Oxide (WO3) and Iron-doped (10 at%) Tungsten Oxide (WO3:Fe) nanostructured thin films were prepared using a dual crucible Electron Beam Evaporation techniques. The films were deposited at room temperature in high vacuum condition on glass substrate and post-heat treated at 300 oC for 1 hour. From the study of X-ray diffraction and Raman the characteristics of the as-deposited WO3 and WO3:Fe films indicated non-crystalline nature. The surface roughness of all the films showed in the order of 2.5 nm as observed using Atomic Force Microscopy (AFM). X-Ray Photoelectron Spectroscopy (XPS) analysis revealed tungsten oxide films with stoichiometry close to WO3. The addition of Fe to WO3 produced a smaller particle size and lower porosity as observed using Transmission Electron Microscopy (TEM). A slight difference in optical band gap energies of 3.22 eV and 3.12 eV were found between the as-deposited WO3 and WO3:Fe films, respectively. However, the difference in the band gap energies of the annealed films were significantly higher having values of 3.12 eV and 2.61 eV for the WO3 and WO3:Fe films, respectively. The heat treated samples were investigated for gas sensing applications using noise spectroscopy and doping of Fe to WO3 reduced the sensitivity to certain gasses. Detailed study of the WO3 and WO3:Fe films gas sensing properties is the subject of another paper.

Eyelid pressure on the cornea

The eyelids play an important role in lubricating and protecting the surface of the eye. Each blink serves to spread fresh tears, remove debris and replenish the smooth optical surface of the eye. Yet little is known about how the eyelids contact the ocular surface and what pressure distribution exists between the eyelids and cornea. As the principal refractive component of the eye, the cornea is a major element of the eye’s optics. The optical properties of the cornea are known to be susceptible to the pressure exerted by the eyelids. Abnormal eyelids, due to disease, have altered pressure on the ocular surface due to changes in the shape, thickness or position of the eyelids. Normal eyelids also cause corneal distortions that are most often noticed when they are resting closer to the corneal centre (for example during reading). There were many reports of monocular diplopia after reading due to corneal distortion, but prior to videokeratoscopes these localised changes could not be measured. This thesis has measured the influence of eyelid pressure on the cornea after short-term near tasks and techniques were developed to quantify eyelid pressure and its distribution. The profile of the wave-like eyelid-induced corneal changes and the refractive effects of these distortions were investigated. Corneal topography changes due to both the upper and lower eyelids were measured for four tasks involving two angles of vertical downward gaze (20° and 40°) and two near work tasks (reading and steady fixation). After examining the depth and shape of the corneal changes, conclusions were reached regarding the magnitude and distribution of upper and lower eyelid pressure for these task conditions. The degree of downward gaze appears to alter the upper eyelid pressure on the cornea, with deeper changes occurring after greater angles of downward gaze. Although the lower eyelid was further from the corneal centre in large angles of downward gaze, its effect on the cornea was greater than that of the upper eyelid. Eyelid tilt, curvature, and position were found to be influential in the magnitude of eyelid-induced corneal changes. Refractively these corneal changes are clinically and optically significant with mean spherical and astigmatic changes of about 0.25 D after only 15 minutes of downward gaze (40° reading and steady fixation conditions). Due to the magnitude of these changes, eyelid pressure in downward gaze offers a possible explanation for some of the day-to-day variation observed in refraction. Considering the magnitude of these changes and previous work on their regression, it is recommended that sustained tasks performed in downward gaze should be avoided for at least 30 minutes before corneal and refractive assessment requiring high accuracy. Novel procedures were developed to use a thin (0.17 mm) tactile piezoresistive pressure sensor mounted on a rigid contact lens to measure eyelid pressure. A hydrostatic calibration system was constructed to convert raw digital output of the sensors to actual pressure units. Conditioning the sensor prior to use regulated the measurement response and sensor output was found to stabilise about 10 seconds after loading. The influences of various external factors on sensor output were studied. While the sensor output drifted slightly over several hours, it was not significant over the measurement time of 30 seconds used for eyelid pressure, as long as the length of the calibration and measurement recordings were matched. The error associated with calibrating at room temperature but measuring at ocular surface temperature led to a very small overestimation of pressure. To optimally position the sensor-contact lens combination under the eyelid margin, an in vivo measurement apparatus was constructed. Using this system, eyelid pressure increases were observed when the upper eyelid was placed on the sensor and a significant increase was apparent when the eyelid pressure was increased by pulling the upper eyelid tighter against the eye. For a group of young adult subjects, upper eyelid pressure was measured using this piezoresistive sensor system. Three models of contact between the eyelid and ocular surface were used to calibrate the pressure readings. The first model assumed contact between the eyelid and pressure sensor over more than the pressure cell width of 1.14 mm. Using thin pressure sensitive carbon paper placed under the eyelid, a contact imprint was measured and this width used for the second model of contact. Lastly as Marx’s line has been implicated as the region of contact with the ocular surface, its width was measured and used as the region of contact for the third model. The mean eyelid pressures calculated using these three models for the group of young subjects were 3.8 ± 0.7 mmHg (whole cell), 8.0 ± 3.4 mmHg (imprint width) and 55 ± 26 mmHg (Marx’s line). The carbon imprints using Pressurex-micro confirmed previous suggestions that a band of the eyelid margin has primary contact with the ocular surface and provided the best estimate of the contact region and hence eyelid pressure. Although it is difficult to directly compare the results with previous eyelid pressure measurement attempts, the eyelid pressure calculated using this model was slightly higher than previous manometer measurements but showed good agreement with the eyelid force estimated using an eyelid tensiometer. The work described in this thesis has shown that the eyelids have a significant influence on corneal shape, even after short-term tasks (15 minutes). Instrumentation was developed using piezoresistive sensors to measure eyelid pressure. Measurements for the upper eyelid combined with estimates of the contact region between the cornea and the eyelid enabled quantification of the upper eyelid pressure for a group of young adult subjects. These techniques will allow further investigation of the interaction between the eyelids and the surface of the eye.

PDMS spreading morphological patterns on substrates of different hydrophilicity in air vacuum and water

In paper has been to investigate the morphological patterns and kinetics of PDMS spreading on silicon wafer using combination of techniques like ellipsometry, atomic force microscope (AFM), scanning electron microscope (SEM) and optical microscopy. A macroscopic silicone oil drops as well as PDMS water based emulsions were studied after deposition on a flat surface of silicon wafer in air, water and vacuum. our own measurements using an imaging ellipsometer, which also clearly shows the presence of a precursor film. The diffusion constant of this film, measured with a 60 000 cS PDMS sample spreading on a hydrophilic silicon wafer, is Df = 1.4  10-11 m2/s. Regardless of their size, density and method of deposition, droplets on both types of wafer (hydrophilic and hydrophobic) flatten out over a period of many hours, up to 3 days. During this process neighbouring droplets may coalesce, but there is strong evidence that some of the PDMS from the droplets migrates into a thin, continuous film that covers the surface in between droplets. The thin film appears to be ubiquitous if there has been any deposition of PDMS. However, this statement needs further verification. One question is whether the film forms immediately after forced drying, or whether in some or all cases it only forms by spreading from isolated droplets as they slowly flatten out.

Development of a method to measure upper eyelid pressure on the cornea

Purpose: The cornea is known to be susceptible to forces exerted by eyelids. There have been previous attempts to quantify eyelid pressure but the reliability of the results is unclear. The purpose of this study was to develop a technique using piezoresistive pressure sensors to measure upper eyelid pressure on the cornea. Methods: The technique was based on the use of thin (0.18 mm) tactile piezoresistive pressure sensors, which generate a signal related to the applied pressure. A range of factors that influence the response of this pressure sensor were investigated along with the optimal method of placing the sensor in the eye. Results: Curvature of the pressure sensor was found to impart force, so the sensor needed to remain flat during measurements. A large rigid contact lens was designed to have a flat region to which the sensor was attached. To stabilise the contact lens during measurement, an apparatus was designed to hold and position the sensor and contact lens combination on the eye. A calibration system was designed to apply even pressure to the sensor when attached to the contact lens, so the raw digital output could be converted to actual pressure units. Conclusions: Several novel procedures were developed to use tactile sensors to measure eyelid pressure. The quantification of eyelid pressure has a number of applications including eyelid reconstructive surgery and the design of soft and rigid contact lenses.

The effect of monocular and binocular cataract blur on postural stability among older adults

Purpose: First-eye cataract surgery can reduce the rate of falls among older adults, yet the effect of second-eye surgery on the rate of falling remains unclear. The present study investigated the effect of monocular and binocular simulated cataract blur on postural stability among older adults. Methods: Postural stability was assessed on 34 healthy older adults (mean 68.2 years, SD 3.5) with normal vision, using a portable force platform (BT4, HUR Labs, Finland) which collected data on centre of pressure (COP) displacement. Stability was assessed on firm and foam surfaces under four binocular viewing conditions using Vistech filters to simulate cataract blur: [1] best-corrected vision both eyes; [2] blur over non-dominant eye, [3] blur over dominant eye and [4] blur over both eyes. Binocular logMAR visual acuity, Pelli-Robson contrast sensitivity and stereoacuity were also measured under these viewing conditions and ocular dominance measured using the hole-in-card test. Generalized estimating equations with an exchangeable correlation structure examined the effect of the surface and vision conditions on postural stability. Results: Visual acuity and contrast sensitivity were significantly reduced under monocular and binocular cataract blur compared to normal viewing. All blur conditions resulted in loss of stereoacuity. Binocular cataract blur significantly reduced postural stability compared to normal vision on the firm (COP path length; p=0.013) and foam surface (anterior-posterior COP RMS, COP path length and COP area; p<0.01). However, no significant differences in postural stability were found between the monocular blur conditions compared to normal vision, or between the dominant and non-dominant monocular blur conditions on either the firm or foam surfaces. Conclusions: Findings indicate that binocular blur significantly impairs postural stability, and suggests that improvements in postural stability may justify first-eye cataract surgery, particularly during somatosensory disruption. Postural stability was not significantly impaired in the monocular cataract blur conditions compared to the normal vision condition, nor was there any effect of ocular dominance on postural stability in the presence of monocular cataract blur.

Juvenile justice in Queensland and Canada : new legislation reflecting new directions

Due to their similar colonial histories and common law heritage, Australia and Canada provide an ideal comparative context for examining legislation reflecting new directions in the field of juvenile justice. Toward this end, this article compares the revised juvenile justice legislation which came into force in Queensland and Canada in 2003 (Canada, Youth Criminal Justice Act, enacted on 19 February 2002 and proclaimed in force 1 April 2003; Queensland, Juvenile Justice Act, amended 2003). There are a series of questions that could be addressed including: How similar and how sweeping have been the legislative changes introduced in each jurisdiction?; What are likely to be some of the effects of the implementation of these new legislative regimes?; and, how well does the legislation enacted in either jurisdiction address the fundamental difficulties experienced by children who have been caught up in juvenile justice systems? This article addresses mainly the first of these questions, offering a systematic comparison of recent Queensland and Canadian legislative changes. Although, due to the recentness of these changes, there is no data available to assess long-term effects, anecdotal evidence and preliminary research findings from our comparative study are offered to provide a start at answering the second question. We also offer critical yet sympathetic comments on the ability of legislation to address the fundamental difficulties experienced by children caught up in juvenile justice systems. Specifically, we conclude that while more than simple legislative responses are required to address the difficulties faced by youth offenders, and especially overrepresented Indigenous young offenders, the amended Queensland and new Canadian legislation appear to provide some needed reforms that can be used to help address some of these fundamental difficulties.

Curriculum design innovation in flexible science teaching

In this paper you will be introduced to a number of principles which can be used to inform good teaching practice and rigorous curriculum design. Principles relate to: * Application of a common sequence of events for how learners learn; * Accommodating different learning styles; * Adopting a purposeful approach to teaching and learning; * Using assessment as a central driving force in the curriculum and as an organising structure leading to coherence of teaching and learning approach; and * The increasing emphasis that is being placed on the development of generic graduate competencies over and above discipline content knowledge. The principles are particularly significant in relation to adult learning. The paper will use three specific applications as illustrations to help you to learn how these principles can be applied. The illustrations are taken from a second year subject in supercomputing that uses scientific case studies. The subject has been developed (with support from Silicon Graphics Inc. and Intel) to be taught entirely via the Internet.

To work or not to work? Child development and maternal labor supply

We estimate the effect of early child development on maternal labor force participation. Mothers of poorly developing children may remain at home to care for their children. Alternatively, mothers may enter the labor force to pay for additional educational and health resources. Which action dominates is the empirical question we answer in this paper. We control for the potential endogeneity of child development by using an instrumental variables approach, uniquely exploiting exogenous variation in child development associated with child handedness. We find that a one unit increase in poor child development decreases maternal labor force participation by approximately 10 percentage points.

Air evacuation in war : the role of RAAF nurses undertaking air evacuation of casualties between 1943-1953

Air transportation of Australian casualties in World War II was initially carried out in air ambulances with an accompanying male medical orderly. By late 1943 with the war effort concentrated in the Pacific, Allied military authorities realised that air transport was needed to move the increasing numbers of casualties over longer distances. The Royal Australian Air Force (RAAF) became responsible for air evacuation of Australian casualties and established a formal medical air evacuation system with trained flight teams early in 1944. Specialised Medical Air Evacuation Transport Units (MAETUs) were established whose sole responsibility was undertaking air evacuations of Australian casualties from the forward operational areas back to definitive medical care. Flight teams consisting of a RAAF nursing sister (registered nurse) and a medical orderly carried out the escort duties. These personnel had been specially trained in Australia for their role. Post-WWII, the RAAF Nursing Service was demobilised with a limited number of nurses being retained for the Interim Air Force. Subsequently, those nurses were offered commissions in the Permanent Air Force. Some of the nurses who remained were air evacuation trained and carried out air evacuations both in Australia and as part of the British Commonwealth Occupation Force in Japan. With the outbreak of the Korean War in June 1950, Australia became responsible for the air evacuation of British Commonwealth casualties from Korea to Japan. With a re-organisation of the Australian forces as part of the British Commonwealth forces, RAAF nurses were posted to undertake air evacuation from Korea and back to Australia from Iwakuni, Japan. By 1952, a specialised casualty staging section was established in Seoul and staffed by RAAF nurses from Iwakuni on a rotation basis. The development of the Australian air evacuation system and the role of the flight nurses are not well documented for the period 1943-1953. The aims of this research are three fold and include documenting the origins and development of the air evacuation system from 1943-1953; analysing and documenting the RAAF nurse’s role and exploring whether any influences or lessons remain valid today. A traditional historical methodology of narrative and then analysis was used to inform the flight nurse’s role within the totality of the social system. Evidence was based on primary data sources mainly held in Defence files, the Australian War Memorial or the National Archives of Australia. Interviews with 12 ex-RAAF nurses from both WWII and the Korean War were conducted to provide information where there were gaps in the primary data and to enable exploration of the flight nurses’ role and their contributions in war of the air evacuation of casualties. Finally, this thesis highlights two lessons that remain valid today. The first is that interoperability of air evacuation systems with other nations is a force multiplier when resources are scarce or limited. Second, the pre-flight assessment of patients was essential and ensured that there were no deaths in-flight.

Impact and energy absorption of empty and foam-filled conical tubes

Foam-filled conical tubes have recently emerged as efficient energy absorbing devices to mitigate the adverse effects of impacts. The primary aim of this thesis was to generate research and design information on the impact and energy absorption response of empty and foam-filled conical tubes, and to facilitate their application in energy absorbing systems under axial and oblique loading conditions representative of those typically encountered in crashworthiness and impact applications. Finite element techniques supported by experiments and existing results were used in the investigation. Major findings show that the energy absorption response can be effectively controlled by varying geometry and material parameters. A useful empirical formula was developed for providing engineering designers with an initial estimate of the load ratio and hence energy absorption performances of these devices. It was evident that foam-filled conical tubes enhance the energy absorption capacity and stabilise the crush response for both axial and oblique impact loading without a significant increase in the initial peak load. This is practically beneficial when higher kinetic energy needs to be absorbed, thus reducing the impact force transmitted to the protected structure and occupants. Such tubes also increase and maintain the energy absorption capacity under global bending as well as minimise the reduction of energy absorption capacity with increasing load angle. Furthermore, the results also highlight the feasibility of adding a foam-filled conical tube as a supplementary device in energy absorbing systems, since the overall energy absorption performance of such systems can be favourably enhanced by only including a relatively small energy absorbing device. Above all, the results demonstrate the superior performance of foam-filled conical tube for mitigating impact energy in impact and crashworthiness applications.

Investigation of mechanisms governing emission of odorants

The literature identifies several models that describe inter-phase mass transfer, key to the emission process. While the emission process is complex and these models may be more or less successful at predicting mass transfer rates, they identify three key variables for a system involving a liquid and an air phase in contact with it: • A concentration (or partial pressure) gradient driving force; • The fluid dynamic characteristics within the liquid and air phases, and • The chemical properties of the individual components within the system. In three applied research projects conducted prior to this study, samples collected with two well-known sampling devices resulted in very different odour emission rates. It was not possible to adequately explain the differences observed. It appeared likely, however, that the sample collection device might have artefact effects on the emission of odorants, i.e. the sampling device appeared to have altered the mass transfer process. This raised the obvious question: Where two different emission rates are reported for a single source (differing only in the selection of sampling device), and a credible explanation for the difference in emission rate cannot be provided, which emission rate is correct? This research project aimed to identify the factors that determine odour emission rates, the impact that the characteristics of a sampling device may exert on the key mass transfer variables, and ultimately, the impact of the sampling device on the emission rate itself. To meet these objectives, a series of targeted reviews, and laboratory and field investigations, were conducted. Two widely-used, representative devices were chosen to investigate the influence of various parameters on the emission process. These investigations provided insight into the odour emission process generally, and the influence of the sampling device specifically.

Influence of smectite suspension structure on sheet orientation in dry sediments : XRD and AFM applications

The structure-building phenomena within clay aggregates are governed by forces acting between clay particles. Measurements of such forces are important to understand in order to manipulate the aggregate structure for applications such as dewatering of mineral processing tailings. A parallel particle orientation is required when conducting XRD investigation on the oriented samples and conduct force measurements acting between basal planes of clay mineral platelets using at. force microscopy (AFM). To investigate how smectite clay platelets were oriented on silicon wafer substrate when dried from suspension range of methods like SEM, XRD and AFM were employed. From these investigations, we conclude that high clay concns. and larger particle diams. (up to 5 μm) in suspension result in random orientation of platelets in the substrate. The best possible laminar orientation in the clay dry film, represented in the XRD 0 0 1/0 2 0 intensity ratio of 47 was obtained by drying thin layers from 0.02 wt.% clay suspensions of the natural pH. Conducted AFM investigations show that smectite studied in water based electrolytes show very long-range repulsive forces lower in strength than electrostatic forces from double-layer repulsion. It was suggested that these forces may have structural nature. Smectite surface layers rehydrate in water environment forms surface gel with spongy and cellular texture which cushion approaching AFM probe. This structural effect can be measured in distances larger than 1000 nm from substrate surface and when probe penetrate this gel layer, structural linkages are forming between substrate and clay covered probe. These linkages prevent subsequently smooth detachments of AFM probe on way back when retrieval. This effect of tearing new formed structure apart involves larger adhesion-like forces measured in retrieval. It is also suggested that these effect may be enhanced by the nano-clay particles interaction.