Flat Tablet Research Articles

Physical Load While Using a Tablet at Different Tilt Angles during Sitting and Standing.

Few standards and guidelines to prevent health problems have been associated with tablet use. We estimated the effects of posture and tablet tilt angle on muscle activity and posture in healthy young adults. Seventeen healthy young adults (age: 20.5 ± 3 years) performed a cognitive task using a tablet in two posture (sitting and standing) and tablet tilt angle (0 degrees and 45 deg) conditions. Segment and joint kinematics were evaluated using 16 inertial measurement unit sensors. Neck, trunk, and upper limb electromyography (EMG) activities were monitored using 12 EMG sensors. Perceived discomfort, kinematics, and EMG activities were compared between conditions using the Friedman test. The perceived discomfort in the standing-0 deg condition was significantly higher than in the remaining three conditions. Standing posture and tablet inclination significantly reduced the sagittal segment and joint angles of the spine, compared with sitting and flat tablet conditions. Similarly, standing posture and tablet inclination significantly reduced EMG activities of the dorsal neck, upper, and lower trunk muscles, while increasing EMG activity of shoulder flexors. Standing posture and tablet inclination reduced the sagittal flexion angle, and dorsal neck, upper, and lower trunk muscle activities, while potentially increasing the muscle activity of arm flexors.

Hybrid Bio-Inspired Structure Based on Nacre and Woodpecker Beak for Enhanced Mechanical Performance.

Materials with high strength and toughness have always been pursued by academic and industrial communities. This work presented a novel hybrid brick-and-mortar-like structure by introducing the wavy structure of the woodpecker beak for enhanced mechanical performance. The effects of tablet waviness and tablet wave number on the mechanical performance of the bio-inspired composites were analyzed. Compared with nacre-like composites with a flat tablet, the strength, stiffness and toughness of the novel hybrid nacre-like composite with tablet wave surface increased by up to 191.3%, 46.6% and 811.0%, respectively. The novel failure mode combining soft phase failure and tablet fracture revealed the key to the high toughness of composites. Finite element simulations were conducted to further explore the deformation and stress distribution of the hybrid brick-and-mortar-like structure. It showed that the hybrid brick-and-mortar-like structure can achieve a much better load transfer, which leads to greater tensile deformation in tablet before fracture, thus improving strength and energy absorption. These investigations have implications in the design of composites with high mechanical performance for aerospace, automobile and other manufacturing industries.

Prediction of tablet characteristics based on sparse modeling for residual stresses simulated by the finite element method incorporating Drucker-Prager cap model

Effects of residual stresses on the mechanical characteristics of tablets such as tensile strength (TS) and disintegration time (DT) were investigated. The residual stresses were simulated using the finite element method (FEM), in which the powder compaction was represented by a Drucker-Prager cap (DPC) model under unconstrained condition. As model tablet formulations, we employed powder mixtures comprising various quantities of lactose (LAC), corn starch (CS), and microcrystalline cellulose (MCC). Key parameters of DPC model were well predicted as a function of quantity ratio of LAC, CS, and MCC. A clear difference was observed in the residual stress distributions between the flat and convex tablets. Strong stresses remained in the convex tablets, while they were rather weak in the flat tablets. For a sparse modeling, an elastic-net (ENET) regression was employed to identify specific stress sites in the tablets. Consequently, the ENET regression revealed specific significant sites in the tablet affecting the TS and DT values. Both quantity and direction of the remaining stresses acting at specific sites close to the die wall were crucial in the convex tablets to predict the TS and DT values; however, no such tendency was seen in the flat tablet.

Application of Terahertz Attenuated Total Reflection Spectroscopy to Detect Changes in the Physical Properties of Lactose during the Lubrication Process Required for Drug Formulation.

Manufacturing the solid dosage form of an orally administered drug requires lubrication to enhance manufacturability, ensuring that critical quality attributes such as disintegration and dissolution of the drug product are maintained during manufacture. Here, to evaluate lubrication performance during manufacture, we used terahertz attenuated total reflection (THz-ATR) spectroscopy to detect differences in the physical characteristics of the lubricated powder. We applied a simple formulation prepared by blending granulated lactose as filler with magnesium stearate as lubricant. A flat tablet was prepared using the lubricated powder to acquire sharp THz-ATR absorption peaks of the samples. First, we investigated the effects of lubricant concentration and compression pressure on preparation of the tablet and then determined the effect of the pressure applied to samples in contact with the ATR prism on sample absorption amplitude. We focused on the differences in the magnitudes of spectra at the lactose-specific frequency. Second, we conducted the dynamic lubrication process using a 120-L mixer to investigate differences in the magnitudes of absorption corresponding to the lactose-specific frequency during lubrication. In both studies, enriching the lubricated powder with a higher concentration of magnesium stearate or prolonging blending time correlated with higher magnitudes of spectra at the lactose-specific frequency. Further, in the dynamic lubrication study, the wettability and disintegration time of the tablets were compared with the absorption spectra amplitudes at the lactose-specific frequency. We conclude that THz-ATR spectroscopy is useful for detecting differences in densities caused by a change in the physical properties of lactose during lubrication.

Numerical Investigation of the Residual Stress Distribution of Flat-Faced and Convexly Curved Tablets Using the Finite Element Method.

The stress distribution of tablets after compression was simulated using a finite element method, where the powder was defined by the Drucker-Prager cap model. The effect of tablet shape, identified by the surface curvature, on the residual stress distribution was investigated. In flat-faced tablets, weak positive shear stress remained from the top and bottom die walls toward the center of the tablet. In the case of the convexly curved tablet, strong positive shear stress remained on the upper side and in the intermediate part between the die wall and the center of the tablet. In the case of x-axial stress, negative values were observed for all tablets, suggesting that the x-axial force always acts from the die wall toward the center of the tablet. In the flat tablet, negative x-axial stress remained from the upper edge to the center bottom. The x-axial stress distribution differed between the flat and convexly curved tablets. Weak stress remained in the y-axial direction of the flat tablet, whereas an upward force remained at the center of the convexly curved tablet. By employing multiple linear regression analysis, the mechanical properties of the tablets were predicted accurately as functions of their residual stress distribution. However, the multiple linear regression prediction of the dissolution parameters of acetaminophen, used here as a model drug, was limited, suggesting that the dissolution of active ingredients is not a simple process; further investigation is needed to enable accurate predictions of dissolution parameters.

Study of the Validity of the Three-Point Bending Test for Pharmaceutical Round Tablets Using Finite Element Method Modeling

Mechanical strength is an important quality attribute of the tablets produced in the pharmaceutical industry. The three-point bending test is one of the methods described by the United States (US) pharmacopeia to test this property. In this work, finite element method modeling was perform to study the stress distribution in a round, flat tablet submitted to this test and to verify whether the equation given by US pharmacopeia to calculate the tensile strength could be used without restrictions. For this test, the center of the lower face of the tablet was submitted to the highest tensile stress and, at this point, the stress state was nearly uniaxial. This test is thus well suited to measure the tensile strength of pharmaceutical tablets. Moreover, simulations were performed with a large range of geometrical dimensions using the dimensionless parameters D/L and h/D (where D is the tablet diameter, h is the tablet thickness, and L is the distance between the supports). In order to obtain the value of the tensile strength with a good precision when using the equation given by the US pharmacopeia, the measurements should only be performed in a restricted area of the domain defined by D/L and h/D.

Internal Multiple-Scattering Hole-Enhanced Raman Spectroscopy: Improved Backscattering Fourier Transform Raman Sampling in Pharmaceutical Tablets Utilizing Cylindrical–Conical Holes

The benefits of Raman signal enhancement and improved measurement precision are demonstrated using 180° backscattering Fourier transform Raman (FT-Raman) spectroscopy from drilled cylindrical-conical holes within pharmaceutical tablet cores. Multiple scattering of the incident laser light within the holes results in an increased Raman signal due to the larger Raman sampling volume. This is important for overcoming typical sub-sampling issues encountered when employing FT-Raman backscattering of heterogeneous pharmaceutical tablets. Hole depth and diameter were found to be important experimental parameters and were optimized to yield the greatest signal enhancement. The FT-Raman spectra collected using backscattering from cylindrical-conical holes is compared to typical 180° backscattering from flat surfaces using tablet cores of Excedrin® and Vivarin®. Raman chemical images are used to establish a representative sampling area. We observe a three- to five-fold increase in the Raman intensity and a two-fold improvement in the measurement precision when sampling from cylindrical-conical holes rather than classic backscattering from flat tablet cores. Self-absorption effects on analyte band ratios are negligible in the fingerprint region but are more significant at the higher near-infrared (NIR) absorbances found in the C-H/O-H/-N-H stretching region. The sampling technique will facilitate developing quantitative FT-Raman methods for application to pharmaceutical tablets using the fingerprint spectral region.

Percolative drug diffusion from cylindrical matrix systems with unsealed boundaries

Release of NaCl in both the axial and radial directions from cylindrical ethyl cellulose tablets were investigated by the alternating ionic current method. The pore structure of the investigated binary mixtures was examined by mercury porosimetry and scanning electron microscopy, and the nm range fractal surface dimension of tablet pore walls was extracted from krypton gas adsorption isotherms. The drug release was shown to consist of two overlapping processes of which the first was ascribed to dissolution of NaCl close to the tablet boundary followed by subsequent diffusion through a thin ethyl cellulose layer and a second from which a porosity percolation threshold of 0.22 could be extracted. As well, a cross-over to effective-medium behaviour at a porosity of approximately 0.44 was observed. The presented findings showed that drug release from matrix tablets with unsealed tablet walls substantially differs from earlier investigated release processes for which the drug has only been allowed to escape through one of the flat tablet surfaces. Thus, the present study brings forward knowledge important for the tailoring of controlled drug delivery vehicles with optimum release patterns.

Percolation phenomena in controlled drug release matrices studied by dielectric spectroscopy and the alternating ionic current method

The combined radial and axial ionic drug release from – as well as the percolating ionic conductivity in – cylindrical tablets was investigated by the alternating ionic current (AIC) method and dielectric spectroscopy (DS), respectively. The binary tablets consisted of mixtures of insulating ethyl cellulose and the poor ionic conductor model drug NaCl at nine different concentrations. We found that the dc conductivity, extracted from DS in a well-defined range of frequencies by a power-law method, could be described by a NaCl volume fraction percolation threshold of ∼0.06 in a 3D conducting network. The low threshold was explained by water-layer-assisted ion conduction in μm-sized ethyl cellulose channels between NaCl grains as probed by Hg porosimetry and SEM. The drug release process, as probed by AIC, could be described by a matrix porosity percolation threshold of 0.22, equivalent to a NaCl volume fraction of ∼0.13. The higher percolation threshold found in the drug release experiments as compared to the DS recordings could be explained by the different probing mechanisms of the analysis methods. The present study should provide valuable knowledge for the analysis of a broad class of ion conducting systems for which the frequency response of the dc ion conductivity is superimposed on other dielectric processes in the dielectric spectrum. It also brings forward knowledge important for the development of controlled drug-delivery vehicles as the presented findings show that the drug release from matrix tablets with unsealed tablet walls substantially differs from earlier investigated release processes for which the drug has only been allowed to escape through one of the flat tablet surfaces.

MONUMENT 65

Monument 65, thus far the largest sculpture discovered from the almost completely destroyed site of Kaminaljuyu, has much to tell us about the enigma of this ancient city. Carvings on two sides of the flat tablet resonate with the most sacred concepts of the “Miraflores” people of Late Preclassic Kaminaljuyu. Partly because of the highly problematical picture further field archaeology can provide of Kaminaljuyu—a picture already problematical—but also because of the inherent value of a comparative orientation, I employ an explicitly comparative approach in order to speculate about the ideology encoded on the monument. According to such a comparative perspective, the depictions identify Kaminaljuyu rulers as conventional world- or cosmos-creators and sustainers, functions realized by the sacrifices of royal proxy victims or “twins” of the ruler. The captive scenes, shown on Side A, represent the duality of rulership expressed in a twinship of first, immortal “priest” or administrator—the ruler in his religious role—sacrificing a victim representing a first ideal man or “king,” and, by virtue of this, representing the ever-dying or magical fertility of the polity. On Side B, the creation seems to be manifested or metaphorized by the axis mundi.

A gradient matrix system as a controlled release device. Release from a slab model system

The in vitro release of a model drug compound, acetaminophen, from ethylcellulose matrices was studied. The systems were prepared by spraying a solution of acetaminophen and polymer on to flat tablet surfaces in a spray box. The release from the slabs showed a square root of time dependency for systems containing up to 75% of acetaminophen by weight (relative to weight of ethylcellulose). Addition of a pore-forming material, xylitol, increased the release rate of acetaminophen. Linear release rates were observed by applying a positive concentration gradient of acetaminophen in the direction of the core of the matrix. Xylitol was added with an inverse concentration gradient. Formation of a barrier layer at the outer surface of the device was thus avoided.