Agar-agar Solution Research Articles

F.4 Anatomical assessment and comparative analysis of ventricular access points in pterional approach: a cadaveric study

Background: In early-stage transsylvian aneurysm surgery, achieving brain relaxation is crucial for the safe exposure of aneurysms; however, in cases of tight, hemorrhagic brains, ventricular drainage is often required. Although Paine/Samson initially proposed a ventricular access point in the frontal horn of the lateral ventricle, and numerous points and techniques have been described since, their consistency and success rates have not undergone rigorous evaluation through comparative cadaveric anatomical studies. Methods: We injected 2 cc agar-agar solutions with distinct colors into the lateral ventricles of twelve cadaveric brains, utilizing four described points, followed by refrigeration at 4°C for one hour for each injection. Next, the brains were sectioned in the coronal plane at 2 cm intervals for evaluation. We assessed the efficacy of the injections in reaching the ventricles and measured the ventricular dimensions, in addition to calculating the Evans’ index for each brain. Results: Injections at Paine/Samson’s point achieved a 100% success rate, followed by Hyunn’s point with a 91.6% success rate. The success rates at Temporal point and Park point were 83.3% and 58.3%, respectively. Conclusions: We emphasize the significance of direct ventricle puncture technique and our findings indicate that the classical Paine/Samson point is the most reliable among the evaluated methods.

STUDY OF THE FEATURES OF GEL FORMATION AND RHEOLOGICAL PROP-ERTIES OF HYDROGELS BASED ON AGAR-AGAR

The article shows studies on the study of the kinetics of gelation and the features of the rheological properties of hydrogels based on agar-agar. It has been found that hydrogels have attracted a lot of attention in the last 50 years due to their exceptional wide range of applications. They have a certain degree of elasticity, very similar to natural fabrics due to the high water content. Within the framework of the literature review, it has been shown that polymer hydrogels are usually obtained by polymerization of water-soluble unsaturated compounds in the presence of a bifunctional cross-linking agent or by structuring pre-prepared reactive prepolymers. The ability of polymer hydrogels to undergo bulk transitions between swollen and collapsed phases under the action of an external medium is one of the most important and universal properties of these materials. It has been shown that polymer hydrogels are known that are used as inert matrices for the controlled release of pre-absorbed biologically active substances. In this case, the release rate of the biologically active substance is determined by the nature and structure of the hydrogel polymer framework. The article studies the kinetics of gelation and the features of the rheological properties of hydrogels based on agar-agar in order to obtain modern biocompatible materials for the medical, cosmetological and pharmaceutical industries. It is shown that in compositions that consist exclusively of agar-agar and water, the shortest time for loss of stickiness and film formation is observed. At the same time, with an increase in the content of agar-agar from 25 to 50 %, one can see the most rapid processes of loss of stickiness and film formation. Compositions with the longest time for loss of stickiness and film formation were determined, which contain 25 % agar-agar and 50 % milk and honey, because they will be characterized by a long diffusion time of active substances to the human body. The scientific novelty of the study is related to the study of the effectiveness of gelation in conditions of highly concentrated agar-agar solutions with different contents of the polymer part and active substances, on the basis of which compositions for the preparation of face masks and medical tapes are proposed.

Control of Indentation of a Needle into the Brain Phantom Tissue Using a Piezoelectric Drive

Currently, stereotaxic brain surgery is an actively developing branch of medicine. During these operations, a special needle is inserted into the brain through a hole in the skull. This needle is moved in the brain tissue so that its tip reaches a certain point, after which the necessary medical manipulation is performed (for example, taking a puncture). To ensure accurate positioning of the needle, it is advisable to monitor the process of such operations using the magnetic resonance imaging apparatus. This puts restrictions on the type of actuators that can be used to drive the needle. The paper considers the problem of controlling the penetration of a cylindrical needle into a phantom of the brain where the control force is generated using a piezoelectric drive (PED). To describe the interaction of the needle with the tissue, a phenomenological model is proposed, under which it is assumed that the phantom tissue is a viscoelastic and plastic material, and also demonstrates relaxation properties. When describing forces acting on the lateral surface of the needle from the side of the tissue, the presence of dry friction is taken into account. The proposed model contains a number of parameters that are identified based on experiments carried out at the NCKU (Taiwan). In these experiments, a standard biopsy needle was inserted into a phantom made from agar-agar solution, and the position of the needle and the force acting on it from the tissue were registered. It is shown that the experimental results are in good agreement with the calculations in the context of the model. An algorithm for controlling the needle by setting the frequency of excitation of the probe is proposed. The aim of the control is to introduce the needle to a given depth at a given constant speed, and then hold the needle at this depth. During the process, it is required to avoid overshooting in speed and position. Numerical simulation has been carried out. The effect of the feedback parameters on the nature of the process is investigated. It is shown that the proper choice of parameters allows for avoiding the overshooting.

Abnormal Rheology of Agar-Agar Solutions Prepared Using Water Exposed to an Electromagnetic Field

Abnormal Rheology of Agar-Agar Solutions Prepared Using Water Exposed to an Electromagnetic Field

(S)-Thienyl and (R)-Pirydyl phosphonate Derivatives Synthesized by Stereoselective Resolution of Their Racemic Mixtures With Rhodotorula mucilaginosa (DSM 70403) - Scaling Approaches.

Rhodotorula mucilaginosa was successfully applied as a biocatalyst for the enantioselective resolution of the racemic mixtures of heteroatom phosphonates derivatives, resulting in receiving the following enantiomers: (S)-1-amino-1(2-thienyl)methylphosphonic acid (Product 1) and (R)-1-amino-1-(3′pirydyl) methylphosphonic acid (Product 2). Biological synthesis of both products is reported for the first time. Pure (S)-1-amino-1-(2-thienyl)methylphosphonic acid (Product 1) was isolated with a conversion degree of 50% after 24 h of biotransformation was conducted on a laboratory scale under moderate conditions (1.55 mM of substrate 1, 100 mL of distilled water, 135 rpm, 25°C; Method A). The scale was enlarged to semi-preparative one, using a simplified flow-reactor (Method C; 3.10 mM of substrate 1) and immobilized biocatalyst. The product was isolated with a conversion degree of 50% just after 4 h of biotransformation. Amino-1-(3′pirydyl)methylphosphonic acid (Substrate 2) was converted according to novel procedure, by the immobilized biocatalyst - Rhodotorula mucilaginosa. The process was carried out under moderate conditions (3.19 mM – substrate 2 solution; Method C1) with the application of a simplified flow reactor system, packed with the yeasts biomass entrapped in 4% agar-agar solution. Pure (R)-amino-1-(3′pirydyl)methylphosphonic (50% of conversion degree) was received within only 48 h.

ABNORMAL RHEOLOGY OF AGAR-AGAR SOLUTIONS PREPARED USING WATER EXPOSED TO AN ELECTRO-MAGNETIC FIELD

The paper presents the results of a study of the rheological properties of agar-agar solutions prepared using water exposed to an electromagnetic field with a frequency of 30 to 170 MHz. The studies were carried out at three temperatures: 25, 35, 45 °С, the concentration varied from 0.1 to 0.7%, and the shear rate varied in the range of 100–1000 s-1. As a result of the study, a distinct influence of the electromagnetic field was found, and the quantitative response depends on the shear rate, solution concentration, temperature and frequency of the electromagnetic field. In the vast majority of cases, a decrease in the viscosity of solutions is observed as a result of exposure to an electromagnetic field. There is practically no quantitative correlation of viscosity changes with frequency. There is a complex picture of the mutual influence of the solution concentration, the frequency of the electromagnetic field, temperature and shear rate when measuring viscosity. The temperature dependence of viscosity for solutions subjected to and not exposed to an electromagnetic field is multidirectional in nature and substantially depends on both the concentration of the solution, the frequency of the electromagnetic field, and the shear rate at which measurements were taken.
 An explanation of the observed dependencies is proposed, which is based on the two-component agar-agar solutions, which leads to individualization of the changes in the rheological properties determined by agarose and agaropectin, respectively.

FEATURES OF RHEOLOGY OF AGAR-AGAR SOLUTIONS

The article presents the results of experiments on studying of rheological behaviour of dilute solutions of agar-agar. The chosen range of concentration 0,1–0,7% allows to avoid gelation at ambient temperature. Dependence of viscosity and shear stress on concentration, shearing speed and temperature in an interval 25–45 °С is investigated. It was found that the concentration dependence of viscosity severely depends on the shear speed, a nonlinearity is observed that increases with decreasing shear speed. The dependence of the viscosity on the shear speed for concentrations of 0,3–0,7% has a similar but gradually changing type of the asymptotic decrease, whereas for 0,1%, solution dependence linearly grows with increase of shear speed. The interrelation of viscosity and shear stress is studied. Curves for solutions of 0,3–0,7% have a similar type and differ significantly from curves for 0,1% solutions. Moreover, the dependencies are not typical for polymer solutions. The activation energy of viscosity and shear stress is studied. For two temperature intervals: 25–35 and 35–45 °C, there is no correlation and a smooth dependence of the measured parameters on temperature. The activation energy of both viscosity and shear stress not decreases with temperature increase, as one might expect, but increases, for many times. This fact is observed completely individually for the different concentrations. An explanation is proposed for the observed dependences, which is based on the assumption of a structural change in agar-agar solutions, which is caused by changing the concentration of solution and magnitude of the mechanical influence.

Challenges for Sample Preparation and Analysis of New Matrices During the OPCW Proficiency Tests

Abstract In the OPCW Proficiency Tests usually two sets of three samples each (test sample, control, blank) are sent for analysis, with no indication for the type of the sample. Each set of samples can be prepared in a different matrix, with organic solvent, water and soil as the most frequent ones. Thus each sample has to be analyzed like a test sample. Participants are requested to identify any chemical contained in the schedules of the Chemical Weapons Convention plus all the degradation products that can originate from them; this involves millions of possible chemicals. Usually, a spiking level of ≈10 ppm is applied. Only chemicals that are considered relevant within the scenario of the proficiency test are to be reported. The choice of sample preparation method strongly depends on the composition of the sample and on the requirements for the different analytical techniques employed in the screening and analysis. Because the sample composition of proficiency test samples is unknown, no target compound sample preparation methods can be applied. New matrices, never used in a PT before, required participants to develop new or to adopt existing sample preparation methods. The new matrices from the 38th OPCW PT were linked to food, biodiesel like used cooking oil methyl ester and a 2% Agar-agar solution (solid gel). Aluminium metal and artificial rainwater chosen to provide matrix challenge for the 40th OPCW PT. The paper provides the challenges that are generated by the new and complex matrices, how to work up gel sample, the tendency of biodiesel to form emulsions, how to sub-sample “metal fragments”, and the method of extractions.

STUDY OF VISCOSITY OF AQUEOUS SOLUTIONS OF NATURAL POLYSACCHARIDES

One of the steps of synthesis of biodegradable polymers is preparation of an aqueous solution of raw materials. Formulation of biodegradable films with optimum characteristics requires to undertake a separate rheological study of each aqueous solution. An essential parameter in this step is a uniform thickness, which is achieved by means of specified viscosity parameters. Viscosity of solutions depends on many parameters, among which are composition and concentration of components in a solution, solution preparation temperature, pH of the finished medium, and presence of free ions. This article describes studies and results on study of viscosity parameters of aqueous solutions of natural polysaccharides: agar-agar, hydroxypropyl methyl cellulose and carrageenan. For aqueous solutions of carrageenan and hydroxypropyl methylcellulose, viscosity was measured at 25°C. In addition, viscosity parameters were measured for 1.5% hhydroxypropyl methylcellulose solutions at 40°C and 60°C. Depending on the gel formation temperature, viscosity of agar-agar solutions was measured at 50°C or 70°C. According to the results of experiments, it was found that viscosity of 1.0-1.5% hydroxypropyl methylcellulose aqueous solutions is in the range of 8.0-80.0 cP. Heating to 100°C at pH 6 results in irreversible destruction of hydroxypropylmethylcellulose molecules. Aqueous solutions of agar-agar are similar to hydroxypropyl methylcellulose solutions but agar-agar is able to gelate at sufficiently low concentrations (from 0.5%). Viscosity of 3.0- 5.0% carrageenan aqueous solutions varies within a wide range: 1.5-1400.0 cP. Thus, rheological properties allow to adjust viscosity of the process mixture in the production of biodegradable polymers in the desired range and in different directions.

Training for brain tumour resection: a realistic model with easy accessibility.

Resection of intrinsic and extrinsic brain tumours requires an understanding of sulcal and gyral anatomy, familiarity with tissue consistency and tissue manipulation. As yet, these skills are acquired by observation and supervised manipulation during surgery, thus accepting a potential learning curve at the expense of the patient in a live surgical situation. A brain tumour model could ensure optimised manual skills and understanding of surgical anatomy acquired in an elective and relaxed teaching situation. We report and evaluate a brain tumour model, regarding availability, realistic representation of sulcal and gyral anatomy and tissue consistency. Freshly prepared agar-agar solution with different concentrations was added with highlighter ink and injected into fresh sheep brains. Hardened agar-agar solution formed masses comparable to malignant brain tumours. Variation of the agar-agar concentration influenced diffusion of agar-agar solution in the adjacent brain tissue. Higher concentrated agar-agar solutions formed sharply delimitated masses mimicking cerebral metastases and lower concentrated agar-agar solutions tended to diffuse into the adjacent cerebral tissue. Adding highlighter ink to the agar-agar solution produced fluorescence after blue light excitation comparable to the 5-ALA induced fluorescence of malignant glioma. The described in vitro sheep brain tumour model is simple and realistic, available practically everywhere and cheap. Therefore, it could be useful for young neurosurgical residents to acquire basic neuro-oncological skills, experiencing properties of the cerebral brain texture and its haptic perception and to learn handling of neurosurgical equipment.

Accuracy of electronic apex locators to detect root canal perforations with inserted metallic posts: an ex vivo study.

IntroductionThe detection of possible root canal perforations caused during a metal post placement is frequently difficult to diagnose. The aim of this study was to investigate the accuracy of apex locators to diagnose such perforations.Materials and methodsThirty mesiolingual root canals of extracted mandibular molars were instrumented (30/.04) and a post space was prepared. A root canal perforation was intentionally made at the bi-furcation (n = 15). Metal posts were cemented in 15 perforated and 15 non-perforated root canals. The teeth roots were embedded in an agar-agar solution. The resulting measurements (“short” or “beyond” the apex) disclosed if a perforation could be identified with five different apex locators (ProPex II, Elements Apex Locator, Apex NRG, Raypex 5 and Raypex 6). The sensitivity and specificity (95% interval confidence) were calculated.ResultsAll devices excluded the absence of perforations (100% with 95% confidence interval [78%; 100%] specificity). The Apex NRG and Raypex 6 detected all perforations (100% with 95% confidence interval [78%; 100%] sensitivity). The ProPex II, Elements Apex Locator, and Raypex 5 detected 14 out of 15 perforations (93% with 95% confidence interval [68%; 100%] sensitivity).ConclusionsAll devices determined root canal perforations, due to metallic posts, within clinical acceptable ranges.

Variation in Root Morphological and Physiological Traits and Nutrient Uptake of Chickpea Genotypes

ABSTRACT Plant nutrients such as potassium (K), phosphorus (P), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) mostly remain fixed in soils and their bio-availability to plant roots is diffusion-limited. Hence, superior root traits, that can enhance their dissolution and capture from the soils, can play a central role in its productivity. Root morphological (root length and root hairs) and physiological traits (root exudation of protons and phosphatase enzymes) of ten selected varieties/breeding lines of chickpea (Bari-chhola-3, Bari-chhola-4, Bari-chhola-5, Bari-chhola-6, Bari-chhola-7, Bari-chhola-8, BGM-E7, ICCV-98926, ICCV-94924, and ICCV-98916) were studied and related them to the uptake of the nutrients in a pot experiment. There were significant (P < 0.05) genotypic differences in root length (RL) and root hair length (RHL). The RL ranged between 70 m plant− 1 and 140 m plant− 1. The variation in RHL was significant (P < 0.05) and it ranged between 0.58 ± 0.09 mm (Bari-chhola-5) and 0.26 ± 0.09 mm. The root hair density (RHD, number mm− 1root) varied between 13 ± 2 and 21 ± 3 among the genotypes. The presence of root hairs increased the effective root surface area (e.g., Bari-chhola-5) up to twelve times. The genotypes differed in their ability to acidify the rooting media in laboratory agar studies, with Bari-chhola-5 inducing most acidification followed by Bari-chhola-3. The ability of Bari-chhola-5 to acidify the rhizosphere was also confirmed by embedding in situ roots in the field in an agar-agar solution containing pH indicator dye Bromocresol purple. The genotypes did not differ for induction of acid phosphatase activity (Aptase) in the rooting media. The genotypes inducing greater acidification and possessing prolific root hairs (Bari-chhola-3 and Bari-chhola-5) absorbed significantly higher amounts of the nutrients K, P, Fe, Mn, and Zn, whose availability in soils is usually low. The results suggest that a collective effect of superior morphological and physiological root traits confers better nutrition of chickpea genotypes in low-nutrient soils.

New in vitro micrografting method for apple by sticking

The requirements for in vitro micrografting in apple are described. In vitro multiplicated shoots of cv. Royal Gala were the sources of rootstocks and scions after different pre-treatment, respectively. Oxidative browning of cut surfaces could be inhibited by the use of antioxidant mixture during grafting process. Scion base cut in v-shape was stuck by 1% agar-agar solution into the vertical slit of rootstock. There was no any displacement and the rate of fused and further developed grafts was 95 percent. Agar-agar between the rootstock and scion made the transport of different materials possible and hold the graft units together until the fusion took place. Fusion was proved also by histological studies. Some of in vitro micrografts were planted and acclimatisated and the survival was 100 percent.

Ion chromatographic determination of metals in biocompatibility testing.

The increasing numbers of materials used in surgical implants require a wide spectrum of tests to evaluate their biocompatibility. The release of metals is an important additional feature for determining the suitability for clinical applications of biomaterials such as ceramics and metals. Due to the difficulty of performing time-consuming experiments in vivo, one approach for rapidly determining the suitability of biomaterials and their interactions with the tissues with which they will come in contact is to perform in vitro tests, based on cell culture analysis, using solutions that reproduce the cleavage and binding capabilities of body fluids and tissues. The present work reports on the application of ion chromatography to the simultaneous determination of some metal ions in a few biologic media. Agar-Agar solution, "199 medium, " and betadine and Schiff's reagents were selected as some of the most representative biologic simulating solutions. A method is recommended for the pretreatment of the sample with minimal reagent addition since it is very rich in organic compounds and cannot be analyzed without pretreatment. The proposed procedure requires the sample to be subjected to oxidative UV photolysis for about 60 min in an UV digester at 85 degrees +/- 5 degrees C, followed by the ion chromatographic determination. Lead (II), cadmium (II), iron (III), copper (II), nickel (II), zinc (II), and cobalt (II) simultaneously were determined at microg/L levels.

The Study of The Effect of Concentration of The Agar-Agar Solution on The Rheological and Thermo Rheological Behavior

The purpose of this work is to study the effect of concentration and temperature of agar agar solution on the rheological behavior of a complex fluid (agar agar solution) used on a capillary rheometer. The rheological properties of agar solution were studied, in particular the concentration's effect (0.1%, 0.15%, 0.17% and 0.2%), and temperature (20°C, 30°C, 40°C, 50°C, 60°C and 70 °C) on the rheological behaviour of the agar agar solution. A comparative study of various rheological laws (Herschel-Buckley, Cross, Oswald De Waele, Bingham) was made, to etablish a model that presents the rheological behavior which applies to different samples of agar agar solution, based on the coefficient of correlation. Results indicated that the rheological behavior of agar agar solution depends on the range of shear rate used : for low shear rate (lower than 6.2 s-1) the solution of agar agar can be modeled by an Ostwald-De Waele-type power-law, but for the high shear rate (higher than 6.2 s-1) the solution of agar agar can be described by Bingham's model. The concentration's and temperature's effect of agar agar solution on the two models studies's parameters (Ostwald-De Waele, Bingham) was studied.We observe a decrease of consistency index 'k' as a function of temperature, this decrease is more accentuated for temperatures ranging from 20 to 40 °C. On the other hand, above 40°C the decrease in the consistency index with temperature is less sensitive. The consistency index increases a function of concentration. the increase in the concentration of agar agar has a positive effect on the critical stress and plastic viscosity and the critical constraint ?_c and plastic viscosity ?p at high shear rates, decrease with increasing temperature.

The concentration polarization effect in ion exchange membrane electrodialysis

We have studied the concentration polarizations in the ion exchange membrane electrodialyses including their correlative phenomena. The limiting current densities of the ion exchange membranes were measured in the systems formed with various membranes and solutions. It is stressed that the cation-exchange membranes gave lower values of limiting current densities and a lesser effect on the disturbance of the pH value of the solution than the anion exchange membranes in the NaCl solutions. This result was justified by the following experiments: The cation exchange membranes gave the regular and fast pulse currents while the anion exchange membranes gave only unceasingly generated anomalous currents in the NaCl agar-agar solutions and at the current densities which were much higher than the limiting value.