scholarly journals Synthesis and Characterization of Nanofiber of Oxidized Cellulose from Nata De Coco

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Ditpon Kotatha ◽  
Supitcha Rungrodnimitchai
Keyword(s):  
Reaction Time ◽  
Reaction Times ◽  
Degree Of Polymerization ◽  
Raw Material ◽  
Gravimetric Analysis ◽  
Oxidized Cellulose ◽  
Carboxyl Content ◽  
Cellulose Structure ◽  
Nanofibrous Structure ◽  
The Fourier Transform

Oxidized cellulose (OC) nanofiber was successfully prepared from the dry sheet of Nata De Coco (DNDC) using the mixture system of HNO3/H3PO4–NaNO2for the first time. The carboxyl content of the OC was investigated at different conditions (HNO3/H3PO4ratios, reaction times, and reaction temperatures). The results revealed that the carboxyl content of the OC increased along with the reaction time, which yielded 0.6, 14.8, 17.5, 20.9, 21.0, and 21.0% after 0, 6, 12, 36, and 48 hours, respectively. The reaction yields of the OC ranged between 79% and 85% when using HNO3/H3PO4ratio of 1 : 3, 1.4% wt of NaNO2at 30°C at different reaction times. From the structural analysis, the OC products showed a nanofibrous structure with a diameter of about 58.3–65.4 nm. The Fourier transform infrared spectra suggested the formation of carboxyl groups in the OC after oxidation reaction. The crystallinity and crystalline index decreased with an increase of reaction time. The decrease of crystallinity from oxidation process agreed with the decrease of degree of polymerization from the hydrolysis ofβ-1,4-glycosidic linkages in the cellulose structure. The thermal gravimetric analysis results revealed that the OC products were less thermally stable than the raw material of DNDC. In addition, the OC products showed blood agglutinating property by dropping blood on the sample along with excellent antibacterial activity.

scholarly journals Karakteristik Fisik, Kimia, dan Fungsional Pati Ubi Banggai Asetat pada Berbagai Variasi Waktu Reaksi

2021 ◽  
Vol 40 (4) ◽  
pp. 340
Author(s):  
If'all If'all ◽  
Asriani Hasanuddin ◽  
Abdul Rahim ◽  
Syahraeni Kadir
Keyword(s):  
Reaction Time ◽  
Treatment Time ◽  
Reaction Times ◽  
Degree Of Substitution ◽  
Raw Material ◽  
Physical Chemical ◽  
Randomized Design ◽  
Substitution Degree ◽  
Completely Randomized Design ◽  
The One

Banggai yam plant (endemic in Banggai Kepulauan Regency) is a potential raw material in production of modified starch. The one of techniques to increase the value of starch is modification of starch by acetylation method. This study objectives to determine the physical, chemical and functional characteristics of Banggai acetate yam starch at various reaction times. The study used a Completely Randomized Design with treatment time reaction (T), namely T1: 30 min, T2: 35 min, T3: 40 min, T4: 45 min, T5: 50 min, T6: 55 min. This study was conducted to determine the characteristics of yam acetate starch, which includes percent acetyl, degree of substitution, water and oil holding capacity (WHC/OHC), flammability, solubility, moisture content, ash, fat, protein, starch and amylose starch. The results showed that the longer reaction time under certain conditions will increase the acetyl percent, degree of substitution, WHC, OHC, flareability, solubility but reduce levels of fat, water, ash, fat, protein, starch and amylose starch, yam acetate. In this study at the best reaction time is (50 min), gives the acetyl percent 8.658% and substitution degree of 0.356, the value of WHC, OHC, Swelling ratio and solubility of 32.21%, 30.21%, 1.98 g/g, and 19.17% respectively.

scholarly journals Synthesis and Characterization of Porous CaCO3 Vaterite Particles by Simple Solution Method

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4425
Author(s):  
Renny Febrida ◽  
Arief Cahyanto ◽  
Ellyza Herda ◽  
Vanitha Muthukanan ◽  
Nina Djustiana ◽  
...  
Keyword(s):  
Reaction Time ◽  
Reaction Times ◽  
Chemical Properties ◽  
Raw Material ◽  
Porous Microsphere ◽  
Different Temperatures ◽  
Mixing Method ◽  
Physical And Chemical ◽  
And Chemical Properties

Appropriately engineered CaCO3 vaterite has interesting properties such as biodegradability, large surface area, and unique physical and chemical properties that allow a variety of uses in medical applications, mainly in dental material as the scaffold. In this paper, we report the synthesis of vaterite from Ca(NO3)2·4H2O without porogen to obtain a highly pure and porous microsphere for raw material of calcium phosphate as the scaffold in our future development. CaCO3 properties were investigated at two different temperatures (20 and 27 °C) and stirring speeds (800 and 1000 rpm) and at various reaction times (5, 10, 15, 30, and 60 min). The as-prepared porous CaCO3 powders were characterized by FTIR, XRD, SEM, TEM, and BET methods. The results showed that vaterite with purity 95.3%, crystallite size 23.91 nm, and porous microsphere with lowest pore diameter 3.5578 nm was obtained at reaction time 30 min, temperature reaction 20 °C, and stirring speed 800 rpm. It was emphasized that a more spherical microsphere with a smaller size and nanostructure contained multiple primary nanoparticles received at a lower stirring speed (800 rpm) at the reaction time of 30 min. One of the outstanding results of this study is the formation of the porous vaterite microsphere with a pore size of ~3.55 nm without any additional porogen or template by using a simple mixing method.

Oxidation of Palm Shell Coal Using HNO3/H3PO4-NaNO2 System for Adsorbents

2018 ◽  
Vol 382 ◽  
pp. 312-317 ◽  
Author(s):  
Supitcha Rungrodnimitchai ◽  
Suphatra Hiranphinyophat
Keyword(s):  
Methylene Blue ◽  
Reaction Time ◽  
Optimal Condition ◽  
Langmuir Isotherm ◽  
Reaction Times ◽  
Carboxyl Content ◽  
Methylene Blue Adsorption ◽  
Maximum Capacity ◽  
Palm Shell ◽  
Mixture System

Modified palm shell coal (MPSC) was prepared by using the mixture system of HNO3/H3PO4-Na2NO2 in order to produce adsorbents. The modification of palm shell coal was performed at different conditions including various reaction times and temperatures to find the optimal condition. The carboxyl content of MPSC was investigated by titration and FTIR. Moreover, the morphology of MPSC was studied by SEM. The results revealed that carboxyl content increased with an increase of the reaction time and temperature. The best condition was the reaction at 50°C for 60 hours, which showed the carboxyl content of 4.03 mmol/g. The maximum capacity of methylene blue adsorption increased from 0.86 mg/g to 106.38 mg/g after the modification. The methylene blue adsorption was fitted well to Langmuir isotherm.

Study on Esterification Characteristics of TEMPO-Oxidized Cellulose

2013 ◽  
Vol 749 ◽  
pp. 49-53
Author(s):  
Ai Min Tang ◽  
Kai Wang
Keyword(s):  
Reaction Time ◽  
Acetic Anhydride ◽  
Reaction Temperature ◽  
Influence Factors ◽  
Great Influence ◽  
Functional Materials ◽  
Acid Group ◽  
Oxidized Cellulose ◽  
Carboxyl Content ◽  
Acetyl Group

Oxidized cellulose acetate (OCA) with carboxylic acid group on C-6 position of glucose is a kind of biodegradable functional materials which can be dissolved in organic solvents. First, cellulose was oxidized with TEMPO (2, 2, 6, 6-tetramethyl-piperidyl-1-oxyl) oxidation system, and then OCA was produced via esterification by reacting the oxidized cellulose with acetic anhydride. The influence factors such as carboxylic content of oxidized cellulose, reaction temperature, reaction time, and concentration of acetic anhydride on degree of substitution (DS) of acetyl group and intrinsic viscosity ([η]) of OCA were investigated. The result revealed that the DS of acetyl group can be increased effectively from 2.61 to 2.74 by increasing reaction temperature from 50°C to 80°C, and from 2.58 to 2.72 by prolonging reaction time from 40min to 180min, but the [η] of the product decreased at the same time. An increase in concentration of acetic anhydride led to an increase in DS and [η] of OCA. As the carboxyl content increased from 0.383 mmol/g to 0.797 mmol/g, the DS of acetyl group decreased from 2.81 to 2.73. That result revealed the carboxyl content also has a great influence on the esterification characteristics.

Modeling Within-Person Variance in Reaction Time Data of Older Adults

GeroPsych ◽  
2011 ◽  
Vol 24 (4) ◽  
pp. 169-176 ◽  
Author(s):  
Philippe Rast ◽  
Daniel Zimprich
Keyword(s):  
Reaction Time ◽  
Cognitive Aging ◽  
Reaction Times ◽  
Reaction Time Task ◽  
Reaction Time Data ◽  
Scale Model ◽  
Time Data ◽  
Time Task ◽  
The Mean ◽  
Second Wave

In order to model within-person (WP) variance in a reaction time task, we applied a mixed location scale model using 335 participants from the second wave of the Zurich Longitudinal Study on Cognitive Aging. The age of the respondents and the performance in another reaction time task were used to explain individual differences in the WP variance. To account for larger variances due to slower reaction times, we also used the average of the predicted individual reaction time (RT) as a predictor for the WP variability. Here, the WP variability was a function of the mean. At the same time, older participants were more variable and those with better performance in another RT task were more consistent in their responses.

The Level of Reaction Time Determines the ERP Correlates of Auditory Negative Priming

2006 ◽  
Vol 20 (3) ◽  
pp. 186-194 ◽  
Author(s):  
Susanne Mayr ◽  
Michael Niedeggen ◽  
Axel Buchner ◽  
Guido Orgs
Keyword(s):  
Reaction Time ◽  
Negative Priming ◽  
Effect Size ◽  
Priming Effect ◽  
Reaction Times ◽  
Negative Priming Effect ◽  
Episodic Retrieval ◽  
Time Level ◽  
Fast Reactions ◽  
Priming Condition

Responding to a stimulus that had to be ignored previously is usually slowed-down (negative priming effect). This study investigates the reaction time and ERP effects of the negative priming phenomenon in the auditory domain. Thirty participants had to categorize sounds as musical instruments or animal voices. Reaction times were slowed-down in the negative priming condition relative to two control conditions. This effect was stronger for slow reactions (above intraindividual median) than for fast reactions (below intraindividual median). ERP analysis revealed a parietally located negativity of the negative priming condition compared to the control conditions between 550-730 ms poststimulus. This replicates the findings of Mayr, Niedeggen, Buchner, and Pietrowsky (2003) . The ERP correlate was more pronounced for slow trials (above intraindividual median) than for fast trials (below intraindividual median). The dependency of the negative priming effect size on the reaction time level found in the reaction time analysis as well as in the ERP analysis is consistent with both the inhibition as well as the episodic retrieval account of negative priming. A methodological artifact explanation of this effect-size dependency is discussed and discarded.

The Effect of Retest Practice on the Speed-Ability Relationship

2004 ◽  
Vol 9 (1) ◽  
pp. 24-31 ◽  
Author(s):  
Sybille Rockstroh ◽  
Karl Schweizer
Keyword(s):  
Reaction Time ◽  
Skill Acquisition ◽  
Reaction Times ◽  
Cognitive Tasks ◽  
General Intelligence ◽  
Attention Switching ◽  
Letter Comparison ◽  
Sternberg Paradigm ◽  
The Relationship ◽  
Elementary Cognitive Tasks

Effects of four retest-practice sessions separated by 2 h intervals on the relationship between general intelligence and four reaction time tasks (two memory tests: Sternberg's memory scanning, Posner's letter comparison; and two attention tests: continuous attention, attention switching) were examined in a sample of 83 male participants. Reaction times on all tasks were shortened significantly. The effects were most pronounced with respect to the Posner paradigm and smallest with respect to the Sternberg paradigm. The relationship to general intelligence changed after practice for two reaction time tasks. It increased to significance for continuous attention and decreased for the Posner paradigm. These results indicate that the relationship between psychometric intelligence and elementary cognitive tasks depends on the ability of skill acquisition. In the search for the cognitive roots of intelligence the concept of learning seems to be of importance.

How Useful is the Power Law of Practice for Recognizing Practice in Concentration Tests?

2007 ◽  
Vol 23 (3) ◽  
pp. 157-165 ◽  
Author(s):  
Carmen Hagemeister
Keyword(s):  
Logistic Regression ◽  
Reaction Time ◽  
Power Law ◽  
Error Rate ◽  
Reaction Times ◽  
Practice Effect ◽  
Practice Effects ◽  
Rate Decrease ◽  
Small Practice

Abstract. When concentration tests are completed repeatedly, reaction time and error rate decrease considerably, but the underlying ability does not improve. In order to overcome this validity problem this study aimed to test if the practice effect between tests and within tests can be useful in determining whether persons have already completed this test. The power law of practice postulates that practice effects are greater in unpracticed than in practiced persons. Two experiments were carried out in which the participants completed the same tests at the beginning and at the end of two test sessions set about 3 days apart. In both experiments, the logistic regression could indeed classify persons according to previous practice through the practice effect between the tests at the beginning and at the end of the session, and, less well but still significantly, through the practice effect within the first test of the session. Further analyses showed that the practice effects correlated more highly with the initial performance than was to be expected for mathematical reasons; typically persons with long reaction times have larger practice effects. Thus, small practice effects alone do not allow one to conclude that a person has worked on the test before.

Porous Gel Coatings Obtained by Phase Separation in ORMOSIL System

2000 ◽  
Vol 628 ◽  
Author(s):  
Kazuki Nakanishi ◽  
Souichi Kumon ◽  
Kazuyuki Hirao ◽  
Hiroshi Jinnai
Keyword(s):  
Phase Separation ◽  
Reaction Time ◽  
Volume Fraction ◽  
Sol Gel ◽  
Reaction Times ◽  
Dip Coating ◽  
Coating Solution ◽  
Coating Method ◽  
Gel Phase ◽  
Dip Coating Method

ABSTRACTMacroporous silicate thick films were prepared by a sol-gel dip-coating method accompanied by the phase separation using methyl-trimethoxysilane (MTMS), nitric acid and dimethylformamide (DMF) as starting components. The morphology of the film varied to a large extent depending on the time elapsed after the hydrolysis until the dipping of the coating solution. On a glass substrate, the films prepared by early dipping had inhomogeneous submicrometer-sized pores on the surface of the film. At increased reaction times, relatively narrow sized isolated macropores were observed and their size gradually decreased with the increase of reaction time. On a polyester substrate, in contrast, micrometer-sized isolated spherical gel domains were homogeneously deposited by earlier dippings. With an increase of reaction time, the volume fraction of the gel phase increased, then the morphology of the coating transformed into co-continuous gel domains and macropores, and finally inverted into the continuous gel domains with isolated macropores. The overall morphological variation with the reaction time was explained in terms of the phase separation and the structure freezing by the forced gelation, both of which were induced by the evaporation of methanol during the dipping operation.

scholarly journals Brewers’ spent grain as substrate for dextran biosynthesis by Leuconostoc pseudomesenteroides DSM20193 and Weissella confusa A16

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Prabin Koirala ◽  
Ndegwa Henry Maina ◽  
Hanna Nihtilä ◽  
Kati Katina ◽  
Rossana Coda
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Raw Materials ◽  
Degree Of Polymerization ◽  
Raw Material ◽  
Fermentation Time ◽  
Viscosity Increase ◽  
Spent Grain ◽  
Leuconostoc Pseudomesenteroides ◽  
Weissella Confusa

Abstract Background Lactic acid bacteria can synthesize dextran and oligosaccharides with different functionality, depending on the strain and fermentation conditions. As natural structure-forming agent, dextran has proven useful as food additive, improving the properties of several raw materials with poor technological quality, such as cereal by-products, fiber-and protein-rich matrices, enabling their use in food applications. In this study, we assessed dextran biosynthesis in situ during fermentation of brewers´ spent grain (BSG), the main by-product of beer brewing industry, with Leuconostoc pseudomesenteroides DSM20193 and Weissella confusa A16. The starters performance and the primary metabolites formed during 24 h of fermentation with and without 4% sucrose (w/w) were followed. Results The starters showed similar growth and acidification kinetics, but different sugar utilization, especially in presence of sucrose. Viscosity increase in fermented BSG containing sucrose occurred first after 10 h, and it kept increasing until 24 h concomitantly with dextran formation. Dextran content after 24 h was approximately 1% on the total weight of the BSG. Oligosaccharides with different degree of polymerization were formed together with dextran from 10 to 24 h. Three dextransucrase genes were identified in L. pseudomesenteroides DSM20193, one of which was significantly upregulated and remained active throughout the fermentation time. One dextransucrase gene was identified in W. confusa A16 also showing a typical induction profile, with highest upregulation at 10 h. Conclusions Selected lactic acid bacteria starters produced significant amount of dextran in brewers’ spent grain while forming oligosaccharides with different degree of polymerization. Putative dextransucrase genes identified in the starters showed a typical induction profile. Formation of dextran and oligosaccharides in BSG during lactic acid bacteria fermentation can be tailored to achieve specific technological properties of this raw material, contributing to its reintegration into the food chain.

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