In vitro attenuation of impact shock in equine digits

This study was designed to test the impact characteristics of the equine digit in vitro with the objective of providing a better understanding of the role of the digital structures in the attenuation of impact shock. Uni-axial accelerometers were mounted on cadaver digits on the distolateral hoof wall, the proximolateral hoof wall, the dorsal surface of the second phalanx, and the mid-lateral first phalanx. The hoof-mounted accelerometers were aligned with the hoof tubules while the bone-mounted accelerometers were oriented along the longitudinal axis of the bone. Each digit was mounted in a test apparatus designed to simulate impact of the hoof with the ground during locomotion. The digits were subjected to 3 impact trials against a barrier at each of 3 vertical impact velocities that simulated a forward trotting velocity in the range of 2.67 to 4.46 m/s. The impact deceleration tended to increase with impact velocity. Attenuation of the impact shock by the digital tissues resulted in a reduction in impact decleration in the more proximal measuring locations. The interphalangeal joints appeared to play a larger role in amplitude attenuation than the hoof wall or the soft tissue structures within the hoof wall. The signal frequency data showed that the soft tissues within the hoof acted as a 'lowpass' filter, attenuating the higher deceleration frequencies. The hoof wall and the interphalangeal joints showed little frequency attenuation.     

Ureteral obstruction enhances eicosanoid production in cortical and medullary tubules of rat kidneys

We examined prostaglandin (PG) E2, 6-keto PGF1alpha, and thromboxane B2 (TxB2) production in cortical and medullary tubules from sham-operated control (SOC) rats and rats with bilateral ureteral obstruction (BUO) of 24 h duration. In SOC rats medullary tubules produced significantly greater amounts of the three eicosanoids than cortical tubules. Again, the production of PGE2, 6-keto PGF1alpha, and TxB2 by cortical and medullary tubules was significantly greater in BUO rats than in SOC rats. To elucidate the mechanisms involved, we examined the activity of phospholipase A2 (PLA2) reactive against phosphatidylcholine or phosphatidylethanolamine (PE), the activity of phospholipase C (PLC), and the levels of cyclooxygenase (COX) in cortical and medullary tubules from SOC and BUO rats. In SOC rats the activity of phosphatidylcholine-PLA2 and PE-PLA2, the activity of PLC, and the mass of COX were significantly greater in medullary tubules than in cortical tubules. On the other hand, the activity of PLC in membranes of cortical tubules and the activity of PE-PLA2 and PLC in membranes of medullary tubules, which were in active location, were significantly greater in BUO rats than in SOC rats. COX levels were also significantly greater in cortical and medullary tubules of BUO rats than in those of SOC rats. Thus, we indicate that medullary tubules from SOC rats have greater production of eicosanoids through increased activity of the PLA2 and PLC-COX pathway than cortical tubules from the same group of rats. Again, in rats with BUO, the tubular eicosanoid production may be enhanced via activation of the PLC-COX pathway in cortical tubules or through activation of the PE-PLA2 and PLC-COX pathway in medullary tubules. The enhanced production of tubular eicosanoids observed in rats with BUO may affect tubular function, particularly sodium and water reabsorption.     

A permeability barrier in the dorsal wall of the equine hoof capsule

The permeability barrier in the dorsal wall of the equine hoof capsule was studied by means of horseradish peroxidase (HRP) in 0.9 N saline solution as a water soluble tracer. Section were treated with 3'3'-diaminobenzidine tetrachloride (DAB) and before dissection the quality of the horn of feet from 10 horses was assessed and given a subjective grade as either good or poor. Blocks of tissue from each horse were left in either an oven at 60 degrees C or in water for 2 weeks before treatment in HRP, sectioning and DAB solution. Regions observed were i) outer surface, ii) outermost layers of the horn, iii) cut edge of the outer layer, iv) inner layer of horn, v) cut edge of the inner layer and vi) laminae. Horn deemed to be normal horn and of good 'quality' showed very slight penetration of HRP 3-5 cell layers deep in the outer layer. The cut edge of the outer layer of the wall of the 'normal' horn also showed minimal penetration of HRP through the intercellular spaces. The cut edge of the inner layers of the wall of normal, good quality horn showed penetration of the tracer up to 20 cell layers deep, with HRP in both the intercellular spaces and within the cells. In contrast, sections of horn from horses with brittle feet showed deep cracks in the outer surface into which the HRP had penetrated. Good quality horn showed no change in the position of the permeability barrier after soaking in water for 14 days, but the brittle horn showed an increase in permeability to HRP. In brittle horn, reaction product was seen deep within the section in the intercellular spaces of the intertubular horn only. Placing horn in an oven had no effect on the permeability barrier. The permeability barrier of the dorsal wall of the equine hoof capsule differs with the layer of the wall. Horn considered to be of poor quality had a weaker permeability barrier than horn of good quality.     

Noninvasive photoelastic method to show distribution of strain in the hoof wall of a living horse

A photoelastic method used for materials testing in industry was adapted to show the distribution of strain through the hoof wall in the living horse. Strain was a change in length per unit length in the material of the loaded hoof wall compared with the unloaded condition. Coloured fringes appeared in the photoelastic plastic where there were differences in strain between adjacent sites (strain gradients) in the hoof. Strain distribution was observed in the shod and unshod hoof wall of the front hooves of 6 sound horses with hooves that appeared 'good' to visual inspection, and one unsound horse with hoof cracks. No significant differences in strains were apparent across the hoof walls of the sound horses when the horses were standing normally. Steep strain gradients were apparent in hooves, associated with defects such as cracks, unstable nail holes, and long toes.     

Fe2O3团粒还原制备中空铁颗粒

采用喷雾造粒制备Fe2O3空心球团粒,团粒经过氢气还原得到中空Fe颗粒,通过扫描电镜(SEM)观察Fe2O3空心球团粒及其截面的形貌,研究还原时间对Fe颗粒形貌与截面形貌的影响;采用激光衍射粒度分析仪对Fe颗粒进行粒径分析;采用比表面及孔隙度分析仪表征Fe颗粒的比表面积;采用CSM-MCT显微硬度仪测量空心球状Fe颗粒球壁的硬度和弹性模量。结果表明:Fe2O3空心球团粒和Fe颗粒均为多孔中空球状结构,球壁上存在大量微孔,中空孔直径和球颗粒直径的比值在0.4～0.5;在650℃下还原,随着还原时间增加(4,5,6 h),球壁晶粒逐步长大,中空球状Fe颗粒的比表面积和粒径逐步减小,球壁趋向致密,硬度和弹性模量提高。     

Finite element analysis of static loading in donkey hoof wall

A finite element model of donkey hoof wall was constructed from measurements taken directly from the hoof capsule of the left forefoot. The model was created with a 2 mm mesh and consisted of 11,608 nodes. A linear elastic analysis was conducted assuming isotropic material properties in response to a 375 newton (N) load, to simulate static loading. The load was applied to the wall via 400 laminae in order to simulate the way in which the pedal bone is suspended within the donkey hoof capsule. Displacement, stress concentration, principal strain, and force distribution across the hoof wall were evaluated. The hoof wall model revealed loading responses that were in broad agreement with previously reported in vivo and modelled observations of the equid hoof. Finite element analysis offers the potential to model hoof wall function at the macroscopic and microscopic level. In this way, it could help to develop further our understanding of the functional relationship between the structural organisation and material properties of the hoof wall.     

Ground reaction forces in horses, assessed from hoof wall deformation using artificial neural networks

An artificial neural network (ANN) was developed to investigate whether hoof wall deformation could be used to determine ground reaction forces (GRF) in horses. The ANN was taught this relationship under certain conditions and was able to generalise this knowledge to conditions for which it was not trained before. To acquire data to train and test the ANN, a horse was equipped with strain gauges attached to the dorsal, lateral and medial parts of the hoof to assess hoof wall deformation. A force plate was used to measure the GRFs. Both hoof wall deformation and GRF were recorded simultaneously at different speeds, gaits, surfaces and loads. An ANN was trained with some of these data, and subsequently provided with strain gauge recordings of strides, not used for training. By comparing the GRF calculated by the ANN based on the hoof wall deformation with that recorded simultaneously by the force plate, the generalisability of the ANN was determined. It was found that an ANN is capable of 'learning' the relationship between hoof wall deformation and GRF, and to generalise it to a wide range of new conditions. This technique enables assessment of GRF under difficult conditions, such as on a treadmill or on surfaces where a force plate cannot be employed.     

Tubule density of the stratum medium of horse hoof

The number of tubules/mm2 (tubule density) of horse hoof horn was quantified in samples taken from the left forefeet of 8 randomly selected slaughterhouse horses in order to establish the normal tubule density characteristics at the midline dead centre (MDC) for the stratum medium of horse hoof. In the past the measurement of tubule distribution within the hoof has lacked objectivity. The horse hoof tubule density results are compared to a recent objective study carried out on pony hoof. A similar 4 zone pattern of tubule density was observed, although the precise zonal boundaries and tubule density values differed to those found for pony hoof. There were significant differences in tubule density between zones. Comparison with pony hoof revealed significant tubule density differences in zones 1, 2 and 4; however, there was no significant difference in zone 3. The existence of a 4 zoned pattern of tubule density for horse hoof, as for pony hoof, has been confirmed.     

Variation in surface strain on the equine hoof wall at the midstep with shoeing, gait, substrate, direction of travel, and hoof shape

Objectives were to examine the deformation of the healthy equine front hoof during locomotion, by recording strains on its outer surface, and to test whether its mechanical behaviour is significantly altered under different locomotory conditions and variation in hoof shape. Strains were recorded in vivo from 5 rosette gauges around the circumference of the right forehooves of 12 horses. The magnitudes and orientations of principal strains at the midstep were compared statistically for different conditions of shoeing (shod vs. unshod), gait (walk vs. trot), substrate (treadmill vs. ground), and direction of travel (straight, right turn, left turn). Principal strains were regressed on 4 variables describing hoof shape-toe length, toe angle, and medial and lateral wall angle--to describe their contribution to variations in strain and hoof deformation. Shoeing did not essentially change the magnitudes of the larger, compressive principal strain, but caused some strain reorientation. Shoes decreased the variation in strains indicating that they tend to stabilise the deformation of the hoof. Strain magnitudes were significantly greater at trot than walk, but there was little change in orientation indicating that the general pattern of deformation of the hoof is constant between these 2 gaits. Strain patterns showed small but significant differences between locomotion on the treadmill and on ground, with the differences being more apparent at the toe than at the sides of the hoof. When turning, the quarter on the inside of the turn experienced 40% more strain than during straightline motion, while strain was similarly reduced on the opposite quarter. Strain magnitudes increase with toe length and toe angle, but were inversely proportional to medial and lateral angles. The change with toe length correlated with the range of body size of the animals in the sample. The change with toe angle was contrary to that found in in vitro tests. The change with medial and lateral angles indicated that hooves with more upright quarters are stiffer and possibly provide less impact absorption.     

Characterization of the ntrBC genes of Azospirillum brasilense Sp7: their involvement in the regulation of nitrogenase synthesis and activity

The in vitro effect of citric acid application on periodontally involved root surfaces was investigated using scanning electron microscopy. Teeth were selected following specific criteria. The specimens were prepared for observation, and the features of the root surface were studied. The results demonstrated that a 3-minute application of citric acid (pH = 1.0) to the root surface after scaling and root planing demineralized the outer root surface, opened the dentinal tubules, and exposed collagen fibers. Scaling and root planing alone left the surface with a smear layer, scattered islands of cementum, and no collagen fibers or exposed dentinal tubules.     

Alteration in the brain content of substance P (1-7) during withdrawal in morphine-dependent rats

OBJECTIVE: To evaluate hoof size, shape, and balance as risk factors for catastrophic musculoskeletal injuries (CMI), including suspensory apparatus failure (SAF) and cannon bone condylar fracture (CDY) in Thoroughbred racehorses. ANIMALS: 95 Thoroughbred racehorses that died between 1994 and 1996. PROCEDURE: 38 quantitative measures of hoof size, shape, and balance were obtained from orthogonal digital images of the hoof and were compared between case horses with forelimb CMI (70), SAF (43), and CDY (10) injuries and control horses whose death was unrelated to the musculoskeletal system (non-CMI, 25). Comparison of group means between cases and controls was done using ANOVA, and multivariable logistic regression was used to estimate odds ratios. RESULTS: Odds of CMI were 0.62 times lower for a 5mm increase in ground surface width difference and 0.49 times lower for a 100-mm2 increase in sole area difference. Odds of SAF were 6.75 times greater with a 10 degrees increase in toe-heel angle difference and 0.58 times lower with a 100-mm2 increase in sole area difference. Odds of CDY were 0.26 times lower with a 3 degrees increase in toe angle, 0.15 times lower with a 5-mm increase in lateral ground surface width, and 0.35 times lower with a 100-mm2 increase in sole area difference. CLINICAL RELEVANCE: Decreasing the difference between toe and heel angles should decrease risk of SAF for Thoroughbred racehorses and should be considered in addition to increasing toe angle alone to help prevent catastrophic injury. Trimming the hoof to perfect mediolateral symmetry may not be a sound approach to avoiding injury.     

Heat Pipe Augmented Passive Solar System for Heating of Buildings

A passive solar heating system was built using heat pipes bonded to the absorbing surface of a solar collector mounted on the south wall of a building. The heat pipes provided one-way heat transfer from the absorber through the insulated wall of the building to water tanks placed inside the space to be heated. The space was then heated by means of natural convection from the surfaces of the tank. The evaporator and condenser ends of the heat pipe were designed to be connected by means of a flexible hose so that the system could be retrofit to an existing building. Simulations were carried out to match the experimental and simulated results. The conductance values obtained as a result of matching showed good agreement with theoretically calculated values. Potential performance improvements were identified, including increased liquid fill fraction in the heat pipes and increasing the heat transfer surface area of the water tanks at the condenser end of the pipe.     

Atrial fibrillation in hypertension: under recognised or over diagnosed?

Dentin permeability and hypersensitivity are both reduced when the dentinal tubules are occluded. Previous scanning electron microscopic studies showed that Nd:YAG laser could cause melting of dentin and closure of exposed dentinal tubules without dentin surface cracking. Therefore, the aim of the present study was to evaluate the sealing depth of Nd:YAG laser on human dentinal tubules. Thirty-six dentin specimens with exposed dentinal tubule orifices were used in this study. Samples were randomly divided into three groups. Groups A and B were lased by Nd:YAG laser at energy of 30 mJ with 10 pulses/s for a stroke along the dentin surface. Group C was not lased and served as a control. Subsequently, group B was frozen in liquid nitrogen and split by a sharp chisel. Under SEM observation, nonlased specimens showed numerous exposed dentinal tubule orifices, and lased specimens showed melting of dentin and closure of exposed dentinal tubule orifices. The sealing depth of Nd:YAG laser on human dentinal tubules was approximately 4 microns.     

In-vitro permeability of the human nail and of a keratin membrane from bovine hooves: prediction of the penetration rate of antimycotics through the nail plate and their efficacy

In contrast to the partition coefficient octanol/water the molecular size of penetrating drugs has a noticeable influence on the permeability of the human nail plate and a keratin membrane from bovine hooves. The relationship between permeability and molecular weight is founded on well-established theories. The correlation between the permeability of the nail plate and that of the hoof membrane allows a prediction of the nail permeability after determination of the drug penetration through the hoof membrane. The maximum flux of ten antimycotics (amorolfine, bifonazole, ciclopirox, clotrimazole, econazole, griseofulvin, ketoconazole, naftifine, nystatin and tolnaftate) through the nail plate was predicted on the basis of their penetration rates through the hoof membrane and their water solubilities. An efficacy coefficient against onychomycoses was calculated from the maximum flux and the minimum inhibitory concentration. Accordingly, amorolfine, ciclopirox, econazole and naftifine are expected to be especially effective against dermatophytes, whereas in the case of an infection with yeasts only, amorolfine and ciclopirox are promising.     

Dentine hypersensitivity: the effects of brushing desensitizing toothpastes, their solid and liquid phases, and detergents on dentine and acrylic: studies in vitro

Dentine exhibiting symptoms of dentine hypersensitivity has tubules open at the dentine surface and patent to the pulp. The mechanisms whereby dentinal tubules are exposed is ill understood but probably involves a variety of abrasive and/or erosive agents. This study in vitro examined the quantitative and qualitative effects of toothpastes, their solid and liquid phases and detergents on dentine and acrylic. Abrasion of dentine and acrylic were measured by surfometry. Morphological changes to dentine were assessed by scanning electron microscopy. Abrasion of dentine and acrylic by toothpastes increased with increasing brushstrokes with marked differences in the extent of abrasion between different pastes. Brushing dentine with water or detergents produced progressive abrasion but which appeared to plateau around 2 microm loss. Water and detergents produced minimal effects on acrylic. At 5000 strokes dentine abrasion by solid phases was less than the parent toothpastes but the ranking order of abrasivity was the same as the parent toothpastes. Loss of dentine produced by liquid phases was minimal and in the order of 1-2 microm. Observationally, all toothpastes removed at least the dentine smear layer to expose many tubules; with one desensitizing product leaving a particulate deposit occluding most tubules. The solid phases of the toothpaste produced identical morphological changes to the parent paste. The liquid phases and detergents all exposed dentinal tubules by 5000 strokes. Water had little or no effect on the dentine smear layer. It is concluded that toothpastes, solid phase, liquid phase and detergents have the potential to abrade or erode dentine to a variable degree and result in tubule exposure. The effects of the liquid phases and detergents appear limited to the removal of the smear layer. Such detrimental effects seen in vitro could have relevance to the aetiology and management of dentine hypersensitivity. Toothpaste formulations which despite exposing tubules have ingredients capable of occluding tubules may be an area of development for such products.     

Agglutination behavior of mesophilic starter cultures as a function of proteolysis

The blood supply in the equine hoof was studied by a microvascular casting corrosion technique and scanning electron microscopy in combination with observations of sections of the decalcificated digit. The dermal lamella was observed at the hoof wall and the dermal papilla at the other parts of the hoof. The microvascular architecture of the dermal lamella differed from that of dermal papilla. The vascular cast in the dermal papillar regions indicated that each papilla contained two central vessels (artery and vein), which ran parallel to each other, and the capillary plexus surrounding these vessels. In the dermal lamella region, the vessels consisted of thin parallel sheets arranged in vertical rows. Each sheet was made of branched arteries and veins, both of which were sandwiched between capillary plexus. At the distal and proximal parts of the wall, the vascular casts of the papillae merged to form the vascular sheets of the dermal lamella.     

Effects of season and diet on tensile strength and mineral content of the equine hoof wall

Studies evaluating nutritional and seasonal influences on hoof strength and composition in horses, as well as the scientific justification for feeding supplements to improve hoof quality, are lacking. The horseman and veterinarian need controlled studies in this area to make informed decisions. This project quantified, in 2 trials, relative elasticity, tensile strength, % moisture, and mineral composition of hooves of 48 mature Thoroughbred mares maintained on different nutritional/management regimens, sampled quarterly over 12 month periods. Tensile strength was positively associated with sulphur content. Per cent moisture was not significantly associated with tensile strength, relative elasticity, or mineral content measures. Results indicated that both seasonal trends and nutritional regimes greatly affected hoof wall strength and mineral composition.     

喷雾干燥法制备中空偏钨酸铵球及中空结构形成机理

WO_3基纳米材料具有光催化降解、光解水、电致变色、热致变色和光致变色等特性,在光催化剂、新能源制备、智能窗口、传感器和平板显示器等领域有广泛的应用前景。采用喷雾干燥法成功制备了中空偏钨酸铵球,分析了其制备过程和中空结构的形成机理。结果表明:采用喷雾干燥法制备的中空偏钨酸铵球球体平均粒径为1.03μm,壁厚约为100 nm;其制备过程分为雾化、闪蒸干燥形成壳、中空结构形成3个阶段;干燥塔内由于热空气初始温度为130℃,远高于水的沸点,使液滴表面的水分迅速蒸发,由于蒸发速度非常快,从而在液滴表面结晶而形成壳,进而形成空心结构。     

37Mn5钢管内壁鳞片状缺陷原因分析及改进措施

针对37Mn5钢管生产过程中,管坯穿管后钢管内壁出现大量鳞片状缺陷的情况,采用宏观观察、化学分析、微观分析等方法对鳞片状缺陷产生的原因进行研究。结果表明,37Mn5钢管内壁存在多种大型夹杂物,管坯在进行穿管时,随着管壁厚度的减小,夹杂物会导致钢管内壁产生鳞片状缺陷。采取减少钢中大型夹杂物含量等改进措施后,钢管内壁鳞片状缺陷明显减少。     

Preconditioning with 15-minute ischemia extends myocardial infarct size after subsequent 30-minute ischemia in rabbits

In an attempt to compare the morphology of the resin-dentin interface in areas where the dentinal tubules run perpendicularly or at an angle to the cavity surface with that of areas where they run parallel to it, we studied a dentin adhesive system using transmission electron microscopy and fluorescence confocal laser scanning microscopy. The design of the study included the simulation of the normal hydrostatic pressure within the pulp and the dentinal tubules. Following acid etching of the dentinal surface with maleic acid/HEMA, the smear layer was removed, and a superficial zone was demineralized in such a way that the exposed collagenous dentin matrix retained its integrity. Confocal laser scanning microscopal investigations using primer labeled with rhodamine B showed that the penetration of the primer occurred not only vertically via surface porosities, but mainly laterally, via the dentinal tubules. The adhesive resin labeled with fluorescein completely infiltrated the demineralized layer, thereby forming a hybrid layer. The orientation of the dentinal tubules had a profound effect on the formation of the hybrid layer. In areas with perpendicular tubule orientation, the layer was 3.2 +/- 0.8 microns thick, showing solid 27.2 +/- 0.8 microns long resin tags in the dentinal tubules, and a network of tiny tags in their side-branches. In areas with parallel tubule orientation the layer was significantly thinner (1.3 +/- 0.6 microns) and resin tags were absent.