Good flow and compaction properties are necessary for the manipulation of particulate material in the pharmaceutical industry. The influence of the addition of an alternative sweetener, rebaudioside A, in a concentration 0.2% w/w and 0.5% w/w on the flow, shear and compaction properties of sorbitol for direct compaction, Merisorb® 200, was investigated in this work. Rebaudioside A worsened the flow properties of sorbitol: the Hausner ratio, the compressibility index and the mass flow rate through the aperture of a model hopper. Using a Jenike shear cell revealed a significant increase in cohesion leading to the decrease of the flow function; moreover, the addition of rebaudioside A increased the total energy for compression of tablets and plasticity estimated by the force-displacement method. Finally, the tablets showed a higher tensile strength and needed longer time to disintegrate compared to the tablets made of sorbitol itself. In view of the results for the free-flowable excipient, sorbitol, the effects of stevia even for a 0.2% w/w concentration have to be carefully considered, particularly whenever used in pharmaceutical formulations of poor flow properties.
- MeSH
- Diterpenes, Kaurane chemistry MeSH
- Technology, Pharmaceutical methods MeSH
- Tensile Strength MeSH
- Excipients chemistry MeSH
- Drug Compounding methods MeSH
- Sweetening Agents chemistry MeSH
- Sorbitol chemistry MeSH
- Stevia chemistry MeSH
- Tablets chemistry MeSH
- Pressure MeSH
- Publication type
- Journal Article MeSH
Osteoporosis-related vertebral body fractures involve large compressive strains of trabecular bone. The small strain mechanical properties of the trabecular bone such as the elastic modulus or ultimate strength can be estimated using the volume fraction and a second order fabric tensor, but it remains unclear if similar estimations may be extended to large strain properties. Accordingly, the aim of this work is to identify the role of volume fraction and especially fabric in the large strain compressive behavior of human trabecular bone from various anatomical locations. Trabecular bone biopsies were extracted from human T12 vertebrae (n=31), distal radii (n=43), femoral head (n=44), and calcanei (n=30), scanned using microcomputed tomography to quantify bone volume fraction (BV/TV) and the fabric tensor (M), and tested either in unconfined or confined compression up to very large strains (∼70%). The mechanical parameters of the resulting stress-strain curves were analyzed using regression models to examine the respective influence of BV/TV and fabric eigenvalues. The compressive stress-strain curves demonstrated linear elasticity, yielding with hardening up to an ultimate stress, softening toward a minimum stress, and a steady rehardening followed by a rapid densification. For the pooled experiments, the average minimum stress was 1.89 ± 1.77 MPa, while the corresponding mean strain was 7.15 ± 1.84%. The minimum stress showed a weaker dependence with fabric as the elastic modulus or ultimate strength. For the confined experiments, the stress at a logarithmic strain of 1.2 was 8.08 ± 7.91 MPa, and the dissipated energy density was 5.67 ± 4.42 MPa. The latter variable was strongly related to the volume fraction (R(2)=0.83) but the correlation improved only marginally with the inclusion of fabric (R(2)=0.84). The influence of fabric on the mechanical properties of human trabecular bone decreases with increasing strain, while the role of volume fraction remains important. In particular, the ratio of the minimum versus the maximum stress, i.e., the relative amount of softening, decreases strongly with fabric, while the dissipated energy density is dominated by the volume fraction. The collected results will prove to be useful for modeling the softening and densification of the trabecular bone using the finite element method.
- MeSH
- Models, Biological MeSH
- Biomechanical Phenomena MeSH
- Biomedical Engineering MeSH
- Femur Head physiology MeSH
- Thoracic Vertebrae physiology MeSH
- Bone and Bones anatomy & histology physiology radiography MeSH
- Middle Aged MeSH
- Humans MeSH
- Stress, Mechanical MeSH
- Elastic Modulus MeSH
- Calcaneus physiology MeSH
- Compressive Strength MeSH
- Radius physiology MeSH
- Regression Analysis MeSH
- X-Ray Microtomography MeSH
- Aged, 80 and over MeSH
- Aged MeSH
- In Vitro Techniques MeSH
- Imaging, Three-Dimensional MeSH
- Check Tag
- Middle Aged MeSH
- Humans MeSH
- Male MeSH
- Aged, 80 and over MeSH
- Aged MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
BACKGROUND: Current research implicates interleukin (IL)-6 as a key component of the nervous-system response to injury with various effects. METHODS: We used unilateral chronic constriction injury (CCI) of rat sciatic nerve as a model for neuropathic pain. Immunofluorescence, ELISA, western blotting and in situ hybridization were used to investigate bilateral changes in IL-6 protein and mRNA in both lumbar (L4-L5) and cervical (C7-C8) dorsal root ganglia (DRG) following CCI. The operated (CCI) and sham-operated (sham) rats were assessed after 1, 3, 7, and 14 days. Withdrawal thresholds for mechanical hyperalgesia and latencies for thermal hyperalgesia were measured in both ipsilateral and contralateral hind and fore paws. RESULTS: The ipsilateral hind paws of all CCI rats displayed a decreased threshold of mechanical hyperalgesia and withdrawal latency of thermal hyperalgesia, while the contralateral hind and fore paws of both sides exhibited no significant changes in mechanical or thermal sensitivity. No significant behavioral changes were found in the hind and fore paws on either side of the sham rats, except for thermal hypersensitivity, which was present bilaterally at 3 days. Unilateral CCI of the sciatic nerve induced a bilateral increase in IL-6 immunostaining in the neuronal bodies and satellite glial cells (SGC) surrounding neurons of both lumbar and cervical DRG, compared with those of naive control rats. This bilateral increase in IL-6 protein levels was confirmed by ELISA and western blotting. More intense staining for IL-6 mRNA was detected in lumbar and cervical DRG from both sides of rats following CCI. The DRG removed from sham rats displayed a similar pattern of staining for IL-6 protein and mRNA as found in naive DRG, but there was a higher staining intensity in SGC. CONCLUSIONS: Bilateral elevation of IL-6 protein and mRNA is not limited to DRG homonymous to the injured nerve, but also extended to DRG that are heteronymous to the injured nerve. The results for IL-6 suggest that the neuroinflammatory reaction of DRG to nerve injury is propagated alongside the neuroaxis from the lumbar to the remote cervical segments. This is probably related to conditioning of cervical DRG neurons to injury.
- MeSH
- Enzyme-Linked Immunosorbent Assay MeSH
- Functional Laterality physiology MeSH
- Physical Stimulation MeSH
- In Situ Hybridization MeSH
- Hyperalgesia metabolism MeSH
- Immunohistochemistry MeSH
- Interleukin-6 biosynthesis genetics MeSH
- Cervical Vertebrae MeSH
- Rats MeSH
- Lumbosacral Region MeSH
- Pain Measurement MeSH
- RNA, Messenger biosynthesis genetics MeSH
- Sciatic Neuropathy metabolism MeSH
- Neuralgia metabolism MeSH
- Image Processing, Computer-Assisted MeSH
- Rats, Wistar MeSH
- Receptors, Interleukin-6 biosynthesis genetics MeSH
- Ganglia, Spinal metabolism MeSH
- Constriction, Pathologic MeSH
- Nerve Compression Syndromes metabolism MeSH
- Hot Temperature diagnostic use MeSH
- Blotting, Western MeSH
- Animals MeSH
- Check Tag
- Rats MeSH
- Male MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
This work deals with the mechanical characterization by depth-sensing indentation (DSI) of PLLA and PLDA composites reinforced with micro-particles of Mg (up to 15wt%), which is a challenging task since the indented volume must provide information of the bulk composite, i.e. contain enough reinforcement particles. The composites were fabricated by combining hot extrusion and compression moulding. Physico-chemical characterization by TGA and DSC indicates that Mg anticipates the thermal degradation of the polymers but does not compromise their stability during processing. Especial emphasis is devoted to determine the effect of strain rate and Mg content on mechanical behavior, thus important information about the visco-elastic behavior and time-dependent response of the composites is obtained. Relevant for the intended application is that Mg addition increases the elastic modulus and hardness of the polymeric matrices and induces a higher resistance to flow. The elastic modulus obtained by DSI experiments shows good agreement with that obtained by uniaxial compression tests. The results indicate that DSI experiments are a reliable method to calculate the modulus of polymeric composites reinforced with micro-particles. Taking into consideration the mechanical properties results, PLA/Mg composite could be used as substitute for biodegradable monolithic polymeric implants already in the market for orthopedics (freeform meshes, mini plates, screws, pins, …), craniomaxillofacial, or spine.
OBJECTIVE: To evaluate and compare the viscoelastic properties of dentine and resin-based dental materials by bulk compressive test and the Burgers model. MATERIALS AND METHODS: Sound dentine, three resin composites as well as a resin-based cement were prepared into cylindrical specimens (n = 8). A bulk compressive creep test was applied with a constant load of 300 N (23.9 MPa) for 2 h, followed by another 2 h recovery. The maximum strain, creep stain, percentage of recovery and permanent set was measured using a linear variable displacement transducer. The viscoelastic properties were characterized via the Burgers model, and the instantaneous elastic, viscous as well as elastic delayed deformation were separated from the total strain. Data were analysed via ANOVA (or Welch's Test) and Tukey (or Games-Howell Test) with a significance level of 0.05. RESULTS: Sound dentine presented the lowest maximum strain, creep strain, permanent set and the highest percentage of recovery, followed by 3 resin composites with comparable parameters, while the cement showed a significantly higher maximum strain, permanent set and lower percentage of recovery (p < 0.001). The Burgers model presented acceptable fits for characterization viscoelastic processes of both dentine and resin-based dental materials. Viscous and elastic delayed strain of dentine was significantly lower than those for tested materials (p < 0.001) with the highest instantaneous elastic strain percentage. Similar viscous and delayed strain was found among the 4 resin-based materials (p > 0.05). SIGNIFICANCE: Sound dentine exhibited superior creep stability compared to resin-based dental materials. The viscous deformation in sound dentine could be ignored when loading parallel to dentine tubules.
- MeSH
- Dental Stress Analysis MeSH
- Dentin MeSH
- Humans MeSH
- Elasticity MeSH
- Composite Resins * MeSH
- Materials Testing MeSH
- Dental Materials * MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- MeSH
- Leg pathology MeSH
- Humans MeSH
- Bandages utilization MeSH
- Venous Pressure MeSH
- Venous Insufficiency therapy MeSH
- Check Tag
- Humans MeSH
- Keywords
- komplexní dekongestivní terapie,
- MeSH
- Diagnosis, Differential MeSH
- Drainage MeSH
- Enzyme Therapy MeSH
- Compression Bandages MeSH
- Humans MeSH
- Lymphedema * diagnosis etiology drug therapy surgery classification therapy MeSH
- Disease Management MeSH
- Massage MeSH
- Health Behavior MeSH
- Check Tag
- Humans MeSH
- MeSH
- Diosmin therapeutic use MeSH
- Compression Bandages utilization MeSH
- Humans MeSH
- Risk Factors MeSH
- Varicose Veins etiology prevention & control therapy MeSH
- Health Behavior MeSH
- Venous Insufficiency diagnosis physiopathology therapy MeSH
- Venous Thrombosis diagnosis prevention & control therapy MeSH
- Life Style MeSH
- Check Tag
- Humans MeSH
- Publication type
- Practice Guideline MeSH
[13] s. : il. ; 15 cm
- MeSH
- Patient Compliance MeSH
- Exercise MeSH
- Compression Bandages MeSH
- Health Behavior MeSH
- Venous Insufficiency diagnosis etiology therapy MeSH
- Publication type
- Popular Work MeSH
- Conspectus
- Hygiena. Lidské zdraví
- NML Fields
- angiologie
- zdravotní výchova
- NML Publication type
- informační publikace
