Py Values Research Articles

Comparison of Scheimpflug tomography, Placido disc, and combined Placido Scheimpflug in the measurement of pupil offset in myopic population

IntroductionThis study aimed to compare the consistency of pupil offset measurements obtained using the Pentacam, Keratron Scout, and Sirius devices.MethodsThis retrospective cross-sectional study included 146 young myopic individuals (292 eyes) scheduled for refractive surgery at Dalian Third People’s Hospital between January 2023 and December 2023. Three devices were utilized to measure the chord mu of the pupil deviation along with the Cartesian distances of the X and Y coordinates (Px, Py) associated with the pupil offset. Repeated-measures analysis of variance was used to compare differences in pupil offset acquisition across various devices. Additionally, the intraclass correlation coefficient (ICC) and Bland–Altman plot were utilized to assess the consistency among the three devices.ResultsChord mu, measured using the Pentacam, Keratron Scout, and Sirius devices, were 0.18 ± 0.10, 0.21 ± 0.11, and 0.18 ± 0.11, respectively. The Px values were 0.00 ± 0.14, -0.02 ± 0.16, and -0.01 ± 0.13, respectively, while the Py values were 0.09 ± 0.13, 0.10 ± 0.15, and 0.10 ± 0.13. The ICCs for the three device measurements, chord mu, Px, and Py, were 0.817, 0.900, and 0.855, respectively. When comparing the three devices, the 95% limits of agreement (LoA) for mu and Px measured using the Sirius and Keratron Scout were the narrowest, ranging from −0.15 to 0.08 and −0.11 to 0.13, respectively. Additionally, the 95% LoA for Py measured using the Sirius and Pentacam was the narrowest, ranging from −0.13 to 0.15. The pupil centers in both eyes were predominantly located above the apex of the cornea.ConclusionSirius, Keratron Scout, and Pentacam have good consistency in pupil shift measurement in young myopic patients, and the three devices can be used as references in clinical practice.

Investigations on the Impacts of Drugs or Excipients with Different Physicochemical and Compaction Properties on the Disintegration Behavior of Kollidon®SR-Based Binary Controlled Release Matrix Tablets.

The objective of this study was to examine the impact of the physicochemical properties of the loaded drug or excipient, the concentration of Kollidon®SR (KSR), and the mechanical characteristics of KSR compacts on their disintegration times. Using disintegration apparatus, a two-hour constraint was chosen as the process's end point. Lactose-KSR compacts subjected to the highest compression pressure and Microcrystalline cellulose-KSR compacts with KSR concentrations exceeding 30% exhibited disintegration times of less than ten minutes. Likewise, compacts containing Diltiazem HCl-KSR demonstrated brief disintegration times across all tested KSR concentrations and compression pressures. Compacts of Modafinil, Metformin HCl, and Ascorbic acid-KSR displayed disintegration times ranging from fast to moderate, contingent upon the levels of KSR and compression pressure applied. Compacts containing KSR with Aspirin, Salicylic acid, or Ibuprofen did not exhibit significant disintegration even at minimal amounts of KSR (0.5%). Theophylline-KSR tablets also showed prolonged dissolution times, even at very low concentrations of KSR. The disintegration times of Dic-KSR tablets were roughly close to an hour and were predominantly unaffected by varying KSR levels and only marginally influenced by compression pressures. It is possible to draw the conclusion that different drugs or excipients have different minimum KSR requirements to resist compacts' disintegration process. Compounds that demonstrate low solubility in water can result in extended disintegration times for KSR compacts. The melting points of these compounds, in conjunction with the Py values of the compacts and their compaction properties, could affect the disintegration process, although a precise evaluation is necessary.

Investigations on Compaction Behavior of Kollidon®SR-Based Multi-component Directly Compressed Tablets for Preparation of Controlled Release Diclofenac Sodium.

The physics of tablets mixtures has gained much attention lately. The purpose of this work is to evaluate the compaction properties of Kollidon® SR (KSR) in the presence of different excipients such as Microcrystalline cellulose (MCC), Monohydrous lactose (MH Lactose), Poly (vinyl acetate) (PVA100), and a water-soluble drug Diclofenac sodium (DNa) to prepare once daily formulation. Tablets were prepared using direct compression and were compressed into flat-faced tablets using hydraulic press at various pressures. The combination of MCC and KSR in the tablets showed reduced porosity, and almost constant low Py values as KSR levels increased; also, KSR-DNa tablets had higher percentage porosity and crushing strength values than KSR-MH Lactose tablets. The crushing strengths of KSR-MCC tablets were larger than those of KSR-DNa tablets. Ternary mixture tablets comprised of KSR-MCC-DNa showed decreased porosities and low Py values as the percentage of KSR increased especially at high compression pressures but had higher crushing strengths compared to KSR-DNa or MCC-DNa binary tablets. KSR-MH Lactose-DNa ternary tablets experienced lower porosities and crushing strengths compared to KSR-MCC-DNa tablets. Quaternary tablets of KSR-PVA100-MCC-DNa showed lower porosity and Py values than quaternary tablets obtained using similar proportion of MH Lactose instead of MCC. In conclusion, optimum quaternary tablets were obtained with optimum crushing strengths, relatively low Py, and moderate percentage porosities among all prepared quaternary tablets. The drug release of the optimum quaternary tablets demonstrated similar in vitro release profile compared to that of the marketed product with a mechanism of release that follows Korsmeyer-Peppas model.

Repeatability and Agreement of Chord Mu Between Scheimpflug Tomography and Swept-source Optical Coherence Tomography.

To evaluate repeatability and agreemeny of chord mu between Scheimpflug tomography (Pentacam HR, Oculus Optikgeräte GmbH, Wetzlar, Germany) and swept-source optical coherence tomography-based optical biometer (IOLMaster 700, Carl Zeiss Meditec AG, Jena, Germany). In this retrospective study, 63 eyes of 33 patients were included. Chord mu, X, and Y Cartesian distances between the corneal vertex and the pupil center (Px and Py), and the pupil diameter were compared using two instruments. Repeatability was evaluated using intraclass correlation coefficient (ICC), coefficient of variation (CoV), and within-subject standard deviation (Sw). Inter-device agreement was evaluated using paired t-tests and Bland-Altman plots. Although Sw values for all parameters were similar between the two devices, CoV values of chord mu and pupil diameter were lower, and ICC values of those parameters were higher, in the IOLMaster 700 than in the Pentacam HR. Chord mu and pupil diameter values were higher in IOLMaster 700 than Pentacam HR (p < 0.01). The width of the 95% limit of agreement was wide for all parameters. IOLMaster 700 showed better repeatability than Pentacam HR in chord mu, Px, Py, and pupil diameter values. Because there were statistically significant differences and a low level of agreement in chord mu and pupil diameter values between the two devices, they cannot be used interchangeably.

Mechanical approach for the evaluation of the crispiness of food granular products.

Crispiness of food products is a key parameter for consumer acceptance. Available methods to evaluate this attribute are subjective and have limitations. They are particularly difficult to implement when granular products are considered. The present study aims to provide a physical characterization of the crispiness of food granular products (gari and grinded corn flakes) based on the compression cycle modeling and the determination of the Py (yield pressure) parameter of the Heckel model. High Py values attributed to the brittle behavior, are indicative of product crispiness. Furthermore, Py parameter showed sensitivity to the plasticizing effect of water. This developed physical method was validated through sensory analysis and acoustic measurements which are both considered as reference methods for crispiness evaluation. The brittle/plastic behavior attributed to crispy/non crispy products respectively was confirmed through image analysis using X-ray microcomputed tomography. The latter made it possible to distinguish the brittle from the plastic behavior through the particle size distribution evolution. This work suggests that the Py value is a relevant indicator for the crispiness evaluation of granular products. This physical characterization is expected to contribute in food engineering as an alternative method for granular products crispiness in a simpler and a more objective way.

PACIAE 2.2.1: An updated issue of the parton and hadron cascade model PACIAE 2.2

The parton and hadron cascade model PACIAE 2.2 (cf. Yan et al. (2018) [11]) has been upgraded to the new issue of PACIAE 2.2.1 with the chiral magnetic effect (CME). The charge correlation parameter, γss and γos, which is typically used to “detect” the CME, is calculated by PACIAE 2.2.1 in Au+Au and Pb+Pb collisions, and the result is consistent with the STAR and ALICE data. As an example, PACIAE 2.2.1 model is employed to mimic the pseudorapidity distribution (dNch/dη) and transverse momentum spectra (pT) of charged particles in non-central Au+Au collisions at RHIC energy and Pb+Pb collisions at LHC energy. The chiral magnetic effect is found to partly affect the final-state basic observables in relativistic nuclear collisions. By this new issue a more realistic dynamical evolution of relativistic nuclear collisions can be depicted. Program summaryProgram Title: PACIAE version 2.2.1CPC Library link to program files:https://doi.org/10.17632/w3g68dj4d9.3Code Ocean capsule:https://codeocean.com/capsule/3695338Licensing provisions: CC By 4.0Programming language: FORTRAN 77 or GFORTRANJournal reference of previous version: Comput. Phys. Comm. 224 (2018) 417Does the new version supersede the previous version?: No.Reasons for the new version: In order that PACIAE 2.2.1 model is now able to simulate the CME-related physics and a more realistic dynamical evolution scenario in the relativistic nucleus-nucleus collisions.Summary of revisions: In PACIAE 2.2.1 model the chiral magnetic effect is introduced. The CME-induced charge separation mechanism [7] into the initial partonic states is artificially added by switching py values for a fraction f of the downward moving partons with those of the corresponding upward moving antipartons.Nature of problem: PACIAE is based on PYTHIA, where it has no any mechanisms to generate the chiral magnetic effect (CME). The CME is a novel transport phenomenon arising from the interaction between quantum anomalies and strong magnetic fields in the ultra-relativistic nuclear collisions. Charge separation is an important consequence of the CME. In order to depict the CME, the corresponding upgrade about introducing a global charge separation scheme into the initial partonic states is highly required.Solution method: The global CME-induced charge separation mechanism [7] into the initial partonic states is introduced by switching py values for a fraction f of the downward moving partons with those of the corresponding upward moving antipartons.Additional comments including restrictions and unusual features: PACIAE 2.2.1 has three versions of PACIAE 2.2.1a, 2.2.1b, and 2.2.1c. PACIAE 2.2.1a is for the elementary collision (here no upgraded from PACIAE 2.2a). PACIAE 2.2.1b and PACIAE 2.2.1c are for the nucleus-nucleus collision of A + A with input file of usu.dat. PACIAE 2.2.1b and PACIAE 2.2.1c are similar in the physical contents but are different in the topological structure [8].•Using the attached input file of usux.dat to run 1000 events for the s = 200 GeV Non Single Diffractive pp collision by PACIAE 2.2.1a takes ≈0.5 min.•Using the attached input file of usu.dat to run 10 events for the 35%-45% non-central Au+Au collisions at sNN = 200 GeV by PACIAE 2.2.1b takes ≈6 min.•Using the attached input file of usu.dat to run 10 events for the 35%-45% non-central Au+Au collisions at sNN = 200 GeV by PACIAE 2.2.1c takes ≈8 min.

Design, development, and characterization of an idebenone-loaded poly-ε-caprolactone intravitreal implant as a new therapeutic approach for LHON treatment

Leber's Hereditary Optic Neuropathy (LHON) is a hereditary mitochondrial neurodegenerative disease of unclear etiology and lack of available therapeutic alternatives. The main goal of the current pilot study was based on the evaluation of the feasibility and characteristics of prolonged and controlled idebenone release from a PCL intravitreal implant. The design, development, and characterization of idebenone-loaded PCL implants prepared by an homogenization/extrusion/solvent evaporation method allowed the obtention of high PY, EE and LC values. In vitro characterization was completed by the assessment of mechanical and instrumental properties. The in vitro release of idebenone from the PCL implants was assessed and the implant erosion was monitored by the mass loss and surface morphology changes. DSC was used to estimate stability and interaction among implant’s components. The present work demonstrated the controlled and prolonged idebenone delivery from the PCL implants in an in vitro model. A consistent preclinical base was established, supporting the idea of idebenone-loaded PCL implants as a new strategy of long-term sustained intraocular delivery for the LHON treatment.

Evaluation of Lactose-Based Direct Tableting Agents' Compressibility Behavior Using a Compaction Simulator.

A compaction simulator (CS) is a single-punch instrument that records data during the powder compaction process. The aim of the study was to determine the behavior of lactose-based direct tableting agents (DTAs) by CS. The data recorded were used to evaluate the flowability and compressibility of powders. The focus of the study was on comparing the compressibility of StarLac® [alpha lactose monohydrate (85%) and white maize starch (15%)] and FlowLac®100 (spray-dried alpha lactose monohydrate) in order to make tablets containing poorly flowable paracetamol. Two lactose-based DTAs were used. Physical characterization of these powders was done by measuring bulk, tapped, and true densities alongside scanning electron microscopy analysis. Flow properties were then calculated by the angle of repose, Hausner ratio, and Carr's compressibility index. Force, in-die thickness, and punch displacement data produced by the CS were captured during in-die compression. Compressibility was calculated using the Heckel equation. The physical characterization test results showed no significant difference between the two DTAs. Hardness results revealed that tablet formulations containing FlowLac® had higher sensitivity to an increase in compression force in comparison with StarLac®. From the Heckel plots generated by the CS during the compression cycle, yield pressure (Py) values were calculated for FlowLac®100 and StarLac®. The Heckel parameter (Py) for FlowLac®100 and StarLac® was calculated as 87.5 MPa and 85.2 MPa, respectively, during the compaction cycle at 5 kN. These data indicated that both powders are compressible and have brittle behavior. StarLac® is less brittle, which was shown by its lower sensitivity to compression force. Py values obtained from the Heckel equation described the plasticity of particles, which gives distinct information on the compressibility of both DTAs in real time during the compaction cycle.

Enhanced Characterization of Pyrene Binding in Mixed Cyclodextrin Systems via Fluorescence Spectroscopy.

Although significant effort has been expended to analyze the binding of pyrene in β-cyclodextrin and γ-cyclodextrin, little has been published on the binding of this guest in β-cyclodextrin derivatives (methyl-β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin) or in mixtures of such derivatives, despite the fact that these derivatives are known to have different supramolecular properties that facilitate unique modes of complexation. Reported herein is a detailed spectroscopic investigation of the binding of pyrene in β-cyclodextrin derivatives and in binary mixtures of cyclodextrins. Py values, defined as the ratio of representative vibronic bands in the fluorescence emission of pyrene, were used to measure changes in the pyrene microenvironment in the presence of the cyclodextrin hosts, and indicated that unmodified β-cyclodextrin is unique in providing a fully hydrophobic environment for pyrene through the use of two cyclodextrins to bind a single pyrene guest. By comparison, both γ-cyclodextrin and modified β-cyclodextrin analogues bind pyrene in a less hydrophobic environment through 1:1 binding stoichiometries that allow for continued interactions between the incompletely encapsulated pyrene guest and the aqueous solvent system. Binary mixtures of cyclodextrins were also explored and reinforce the unique properties of the unmodified β-cyclodextrin host. Graphical Abstract The unique binding geometries of pyrene in beta-cyclodextrin and its derivatives leads to measurable fluorescence emission signals, whose information can be used to elucidate the highly structurally dependent binding geometries and stoichiometries.

Source rock potential of the Sayındere formation in the Şambayat oil field, SE Turkey

Upper Campanian–Maastrichtian Sayındere Formation, located in southeastern Turkey, composed of pelagic limestone which was deposited relatively deep marine. In this study, well samples of the Sayındere Formation were analyzed by Rock-Eval pyrolysis and the oil sample from this unit were analyzed by GC, and GC-MS to assess source rock characteristics and hydrocarbon potential. The TOC values of the Sayındere Formation samples range from 0.34 to 4.65 wt.% with an average of 1.14 wt.% and organic matter have good TOC value. Hydrogen Index (HI) values range from 407 mg HC/g TOC to 603 mg HC/g TOC and indicates Type II kerogen. Tmax values are in the range of 434 - 442 °C and indicate early-mid mature stage. The Sayındere samples have fair to good hydrocarbon potential based on TOC contents, S2, and PY values. According to the HI versus TOC plot, most of the samples have good oil source. The oil sample contains predominant short-chain n-alkanes and plots in marine algal Type II field on a Pr/n-C17 versus Ph/n-C18 cross-plot indicating anoxic environment. Biomarker analysis shows that the deposition of oil source rock is carbonate-rich sediments.

Diagnostic criteria for HBV-related acute-on-chronic pre-liver failure

To investigate the diagnostic criteria for HBV-related acute-on-chronic pre-liver failure (pre-ACLF) which can effectively predict the risk of liver failure. A total of 1279 patients with severe icteric chronic hepatitis B (CHB) and/or severe acute exacerbation of CHB were enrolled. The influence of serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total bilirubin (TBil), international normalized ratio (INR) of prothrombin time, sex, and age on the incidence rate of acute-on-chronic liver failure (ACLF) was analyzed, the diagnostic criteria for pre-ACLF and predictive model for ACLF were developed. The chi-square test was used for comparison of categorical variables, and the independent samples t-test was used for continuous data; multivariate logistic regression analysis was performed to evaluate the risk of liver failure. The baseline serum levels of ALT, AST, and TBil, and INR were independent risk factors for liver failure (P < 0.05). The diagnostic criteria for pre-ACLF were as follows: (1) INR≥1.30; (2) AST≥10×upper limit of normal (ULN) and obvious jaundice (TBil≥51.3 μmol/L), or TBil≥342.0 μmol/L. These criteria had a positive predictive value of 45.9%, a negative predictive value of 89.8%, a sensitivity of 69.1%, and a specificity of 76.9%. The predictive model for the risk of ACLF was PY = 1=e(X)/(1+e(X)) (PY represented positive results of logistic regression analysis), X = -10.245+0.026×AST(ULN)-0.025×AST(ULN)+0.046×TBil(mg/dl) + 4.642×INR+0.049×age(years). The patients with higher PY values tended to have a higher incidence rate of ACLF. The incidence rate of ACLF was 75.3% in patients with PY≥0.60, more than 50% in patients with a PY value of 0.40-0.59, and 1.8% in patients with PY < 0.10 (P < 0.01). The diagnostic criteria for pre-ACLF and predictive model can effectively evaluate the risk of HBV-related ACLF.

Compaction behavior and deformation mechanism of directly compressible textured mannitol in a rotary tablet press simulator

Textured mannitol powder is widely used as a pharmaceutical excipient for tablet compaction. In order to choose the right tableting parameters, it is necessary to understand its mechanical behavior during deformation under industrial tableting conditions. The aim of this study was to evaluate the mechanical behavior during deformation of a textured mannitol using a rotary tablet press simulator. Mean yield pressure (Py) obtained by Heckel modeling, Walker coefficients (W) and Stress Rate Sensitivity (SRS) were compared to reference excipients, known for either their plastic (microcrystalline cellulose) or fragmentary (lactose and dibasic calcium phosphate) deformation behavior. Py, W and SRS values showed that the studied textured mannitol has a fragmentary deformation mechanism. Furthermore, this mechanical behavior was not sensitive to lubrication, which is characteristic of fragmentary excipients.

Material, compressional and mechanical properties of &lt;i&gt;Borassus aethiopum&lt;/i&gt; (African fan palm) starches

The compressional and mechanical properties of tablet formulations incorporating native and modified Borassus aethiopum starches as binder were evaluated. The native Borassus aethiopum starch (BAS) was modified to yield fully gelatinised starch (FGBAS) and microcrystalline starch (MBAS). The compressional properties of the starches were evaluated using geometric analysis, Heckel and Kawakita equations, while the mechanical properties were assessed through tensile strength and brittle fracture index determinations. The results show that modification had significant effect on both the compressional and mechanical properties of Borassus native starch (p&lt; 0.05). The modified starches had a lower particle diameter and a corresponding increase in surface properties, and angle of repose. The ranking order for the angle of repose and surface factor is MBAS&gt;FGBAS&gt;BAS, while the ranking order for particle diameter is MBAS&lt;FGBAS&lt;BAS. The ranking order the mean values of the starches is BAS&gt;MBAS&gt;FGBAS, FGBAS with the least py values had the fastest on set of plastic deformation while MBAS with the least pk and BFI values has highest overall plastic deformation, and least tendency to produce tablets with production defects such as capping and lamination. Modified Borassus starches show significant improved mechanical and compressional properties over the native Borassus starch. Keywords: Borassus starches, tablets, compressional and mechanical properties

&lt;b&gt;Method for Evaluating Train Safety in Case of Strong Winds&lt;/b&gt;

This paper proposes a method for evaluating train running safety in strong wind conditions using the probabilities of strong wind occurrence according to wind direction. The Weibull coefficients cd and kd for 16 wind directions were calculated on the basis of data from 10-min maximum instantaneous wind velocities for each wind direction at 772 Automated Meteorological Data Acquisition System (AMeDAS) stations. Probabilities Px of the occurrence of strong winds exceeding the critical wind speeds for overturning were estimated for a train in a virtual railway section by using cd and kd calculated on the basis of the wind data observed at a windy AMeDAS station. Px values were found to vary from 6.2×10-6 to 8.6×10-5 depending on the angle between the traveling direction of the train and each wind direction. The values of Px ranged from 1.4% to 20% of the Py values, which were calculated out of consideration of strong wind occurrence according to wind direction.

Systematic Screening of Compressed ODT Excipients: Cellulosic Versus Non-Cellulosic

The successful development of compressed ODTs utilises low compression forces to create a porous structure whereby excipients are added to enhance wicking/swelling action or provide strength to the fragile tablet framework. In this work, a systematic investigation comparing materials from two different categories was employed to understand their functionality in binary mixture tablets of the most commonly used diluent mannitol. Cellulose based excipients such as HPC (SSL-SFP), L-HPC (NBD-022) and MCC (Avicel PH-102) were compared with non-cellulosic materials such as PEO (POLYOX WSR N-10) and Crospovidone (XL-10). Pure excipient properties were studied using Heckel Plot, compressibility profile, SEM and XRPD, whereas the prepared binary mixture compacts were studied for hardness, disintegration time and friability. Results from our investigation provide insight into differences encountered in product performance of ODT upon inclusion of additional materials. For example, non-cellulosic excipients Polyox and Crospovidone showed higher plasticity (Py values 588 and 450MPa) in pure form but not in binary mixtures of mannitol. Cellulosic excipients, nonetheless, offer faster disintegration (<30 sec) specifically L-HPC and MCC tablets. Disintegration time for tablets with fully substituted-HPC was prolonged (200-500 sec) upon increasing concentration between 1-10% due to gelation/ matrix formation. It can be concluded that despite the reasonably good plasticity of both cellulosic and noncellulosic excipients in pure form, the mechanical strength in binary mixtures is negatively impacted by the fragmentation/ fracture effect of mannitol.

Effects of material properties and speed of compression on microbial survival and tensile strength in diclofenac tablet formulations

A work has been done to study the effects of material properties and compression speed on microbial survival and tensile strength in diclofenac tablet formulations. Tablets were produced from three formulations containing diclofenac and different excipients (DC, DL and DDCP). Two types of machines (Hydraulic hand press and single punch press), which compress the tablets at different speeds, were used. The compression properties of the tablets were analyzed using Heckel and Kawakita equations. A 3-dimensional plot was produced to determine the relationship between the tensile strength, compression speed and percentage survival of Bacillus subtilis in the diclofenac tablets. The mode of consolidation of diclofenac was found to depends on the excipient used in the formulation. DC deformed mainly by plastic flow with the lowest Py and Pk values. DL deformed plastically at the initial stage, followed by fragmentation at the later stage of compression, whereas DDCP deformed mainly by fragmentation with the highest Py and Pk values. The ranking of the percentage survival of B. subtilis in the formulations was DDCP > DL > DC, whereas the ranking of the tensile strength of the tablets was DDCP > DL > DC. Tablets produced on a hydraulic hand press with a lower compression speed had a lower percentage survival of microbial contaminants than those produced on a single punch press, which compressed the tablets at a much higher speed. The mode of consolidation of the materials and the speed at which tablet compression is carried out have effects on both the tensile strength of the tablets and the extent of destruction of microbial contaminants in diclofenac tablet formulations.

Evaluation of Cedrela gum as a binder and bioadhesive component in ibuprofen tablet formulations

The compressional, mechanical and bioadhesive properties of tablet formulations incorporating a new gum obtained from the incised trunk of the Cedrela odorata tree were evaluated and compared with those containing hydroxypropylmethylcellulose (HPMC). Compressional properties were evaluated using Hausner's ratio, Carr's Index, the angle of repose, and Heckel, Kawakita and Gurnham plots. Ibuprofen tablets were prepared using the wet granulation method. Bioadhesive studies were carried out using the rotating cylinder method in either phosphate buffer pH 6.8 or 0.1 M hydrochloric acid media. The gum is a low viscosity polymer (48 cPs), and Fourier transform infrared spectroscopy revealed the presence of a hydroxyl group. Py and Pk values, which are measures of plasticity, showed the gum to be significantly (p&lt;0.05) more plastic than HPMC, and plasticity increased with polymer concentration. All tablet formulations were non-friable (&lt;1.0%), and the formulations containing the gum had a higher crushing strength (130.95 N) than those containing HPMC (117.85 N) at 2.0% w/w binder. Formulations incorporating the gum were non-disintegrating and had a significantly longer drug release time than those containing HPMC. At the highest binder concentration, Cedrela gum formulations adhered to incised pig ileum longer than those containing HPMC. Cedrela gum exhibited better compressive, flow and binding properties than HPMC and is suitable as a bioadhesive and for sustained release of drugs.

New Matrix Tablet from Okra Gum: Effects of Method of Preparation and Gum Concentration on Tablet Properties

The objective of this investigation is to study the effect of methods of preparation and concentration of gum on the compressional and mechanical properties of Okra gum matrix. The compressional behavior of Okra gum matrices prepared by direct compression and wet granulations is analyzed using density measurements, Heckel and Kawakita analysis while the mechanical properties of the formulations were assessed using crushing strength (CS) and friability (FR) as well as CSFR ratio. Formulations prepared by direct compression had lower Pk values than those prepared by wet granulation while there was no significant difference between Py values of formulations prepared by direct compression and wet granulations. Therefore, formulations prepared by direct compression underwent plastic deformation more easily and rapidly than those prepared by wet granulation. The results show that DB values increased with decrease in concentration of the gum and granules undergo higher degree of fragmentation than powders. Formulations containing 90% w/w Okra gum exhibited the highest amount of total plastic deformation and gave the best packing. Tablets prepared by direct compression showed lower bond strength and higher friability values than those prepared by wet granulations. The crushing strength generally decreases with a decrease in the concentration of the gum while there was an inverse relationship between friability and gum concentration. CSFR decreases with a decrease in gum concentration and tablets prepared by wet granulations showed significantly higher values of CSFR (p

Aqueous solutions of lower alcohols investigated by pyrene fluorescence spectroscopy

The aqueous solutions of lower alcohols such as methanol, ethanol, 1-propanol and 2-propanol, were studied by fluorescence spectroscopy of pyrene, defining the Py scale for polarity. Sigmoidal curves were used to fit the Py values of aqueous alcohol solutions as a function of the logarithm of water–alcohol mole ratio, i.e., log(WAR). The results from curve fittings were discussed in terms of the structural transitions of aqueous alcohol solutions, as well as the dissociation constants for alcohol– and water–pyrene complexes. The microscopic alcohol and water phases were considered to be saturated with each other, and the structures of dilute aqueous alcohol solutions were found to be more complicated than those of concentrated ones.

Records of terrestrial sulfur deposition from the latest Permian coals in SW China

Different sulfur fractions of low sulfur (average 0.11%) coals from the latest Permian in southwestern China were analyzed isotopically at a high vertical resolution to examine the ramifications for potential terrestrial extinction mechanisms at the Permo-Triassic boundary. S org (organic sulfur) accounts for 87% of the total sulfur content on average, while S py (pyritic sulfur) is very low (13% of the total sulfur content and ca. 0.01% of the whole sample weight) and relatively constant throughout the profile except for some insignificant additions in clay-rich layers. These indicate the possible differential contribution of local diagenesis during the early stages of peat accumulation. The δ 34S org values have a relatively narrow range, from + 1.5‰ to + 7.6‰, while the δ 34S py values have a wider range, from + 0.8‰ to + 34.1‰, suggesting that pyrite was possibly formed in different stages and that there was negligible bacterial contribution to the primary organic sulfur fraction. Thus, the organic sulfur signal in the coal is largely sourced from the original plant material and records temporal variations in the isotopic composition of the sulfur input to the coal forming environment. The stratigraphically lower coal (B3) has δ 34S org values around + 4‰ while the stratigraphically higher coal (B2), which is closer to the Permian–Triassic boundary, has clearly higher δ 34S org values, ranging from + 5.3 to + 7.6‰. This change is most likely due to increased marine sulfate aerosol inputs into the coal-forming peatland caused by coastline retreat during Late Permian transgression. Importantly, there is no evidence in these discrete intervals of coal formation to indicate a dominant role of atmospheric inputs of isotopically lighter sulfur from either H 2S released from euxinic oceans or volcanic SO 2. This militates against theories that implicate such sources of sulfur in terrestrial extinction mechanisms at the end-Permian.