top of page

グループ

公開·26名のメンバー

Chemical Change V3.0 [Completed] Extra Quality


The chemical changes in skipjack tuna (Katsuwonus pelamis) subjected to cooking, frying, canning and microwave heating were studied. Raw tuna contained an unusual fatty acid C16:3 in high proportion (29.3%) followed by C18:2, C24:1, C16:0 and C18:3. Health beneficial fatty acids, eicosapentaenoic acid (EPA) (1.67%) and docosahexaenoic acid (DHA) (2.50%), were quite low with ω-3/ω-6 ratio 0.28. The total saturated fatty acids suffered major loss in fried (70%) and canned tuna (40%) due to loss of C16:0, C14:0 and C22:0. The monounsaturated fatty acids content increased (38%) in cooked and microwave heated tuna due to C24:1. The polyunsaturated fatty acids content increased in fried (50%) and canned (25%) tuna due to the uptake of frying and filling oil, respectively during processing. The loss of health beneficial ω-3 fatty acids, EPA and DHA were minimum in cooked tuna followed by microwave heated tuna. Canning totally destroyed these fatty acids. In fried tuna, the losses of EPA and DHA were 70 and 85%, respectively. Thiobarbituric acid - reactive substances values increased in heat processed tuna. Cholesterol increased in canned and microwave heated tuna but not in cooked tuna. Reduction of cholesterol in fried tuna was due to its migration into frying oil. This study indicated that cooking and microwave heating are the better processing methods to retain the health beneficial ω-3 fatty acids in comparison to frying and canning.




Chemical Change v3.0 [Completed]



A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another.[1] Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the nuclei (no change to the elements present), and can often be described by a chemical equation. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive elements where both electronic and nuclear changes can occur.


The substance (or substances) initially involved in a chemical reaction are called reactants or reagents. Chemical reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants. Reactions often consist of a sequence of individual sub-steps, the so-called elementary reactions, and the information on the precise course of action is part of the reaction mechanism. Chemical reactions are described with chemical equations, which symbolically present the starting materials, end products, and sometimes intermediate products and reaction conditions.


Most chemical reactions are reversible; that is, they can and do run in both directions. The forward and reverse reactions are competing with each other and differ in reaction rates. These rates depend on the concentration and therefore change with the time of the reaction: the reverse rate gradually increases and becomes equal to the rate of the forward reaction, establishing the so-called chemical equilibrium. The time to reach equilibrium depends on parameters such as temperature, pressure, and the materials involved, and is determined by the minimum free energy. In equilibrium, the Gibbs free energy must be zero. The pressure dependence can be explained with the Le Chatelier's principle. For example, an increase in pressure due to decreasing volume causes the reaction to shift to the side with fewer moles of gas.[16]


Reactions can also be characterized by their internal energy change, which takes into account changes in the entropy, volume and chemical potentials. The latter depends, among other things, on the activities of the involved substances.[19]


Mechanisms of monitoring chemical reactions depend strongly on the reaction rate. Relatively slow processes can be analyzed in situ for the concentrations and identities of the individual ingredients. Important tools of real-time analysis are the measurement of pH and analysis of optical absorption (color) and emission spectra. A less accessible but rather efficient method is the introduction of a radioactive isotope into the reaction and monitoring how it changes over time and where it moves to; this method is often used to analyze the redistribution of substances in the human body. Faster reactions are usually studied with ultrafast laser spectroscopy where utilization of femtosecond lasers allows short-lived transition states to be monitored at a time scaled down to a few femtoseconds.[65]


Fresh fruits and vegetables, when harvested, continue to undergo chemical changes that can cause spoilage and deterioration of the product. This is why these products should be frozen as soon after harvest as possible and at their peak degree of ripeness.


Fresh produce contains chemical compounds called enzymes, which cause the loss of color, loss of nutrients, flavor changes, and color changes in frozen fruits and vegetables. These enzymes must be inactivated to prevent such reactions from taking place.


Let students know that in this chapter they will explore what happens during a chemical change. In a chemical change, the atoms in the reactants rearrange themselves and bond together differently to form one or more new products with different characteristics than the reactants. When a new substance is formed, the change is called a chemical change.


We next compared the performance of standard probes (v2.0) and split-initiator probes (v3.0) in whole-mount chicken embryos (Fig. 3), a representative challenging imaging setting where the sample is thick and autofluorescent. Using standard probes, as the probe set size is increased from 5 to 10 to 20 probes by adding untested probes to a previously validated set of 5 probes (Choi et al., 2016), the background increases dramatically (Fig. 3A, magenta) and the signal-to-background ratio decreases monotonically (Fig. 3B, magenta). Using split-initiator probe pairs that address nearly identical target subsequences, increasing the probe set size causes no measurable change in the background (Fig. 3A, orange) and the signal-to-background ratio increases monotonically (Fig. 3B, orange). Representative images using the largest of these unoptimized probe sets (20 standard probes or 20 split-initiator probe pairs) exhibit high background using standard probes and no visible background using split-initiator probes (Fig. 3C); corresponding pixel intensity histograms for regions of high expression (signal+background) and no or low expression (background) are overlapping using standard probes and non-overlapping using split-initiator probes (Fig. 3D). These data illustrate the significant benefit of automatic background suppression using split-initiator probes: even if there are non-specific probes in the probe set, they do not generate amplified background, so it is straightforward to increase the signal-to-background ratio simply by increasing the probe set size without probe set optimization.


Modern synthetic chemistry. Specific experiments may change from year to year. Ch 5 a focuses on experiments illustrating the multistep syntheses of natural products. Ch 5 b focuses on the synthesis and spectroscopic characterization of coordination and organometallic complexes and their applications in organic and electrochemical catalysis. Methodology will include advanced techniques of synthesis and instrumental characterization. Terms may be taken independently.


A research project carried out under the mentorship of an approved faculty member. Before the beginning of the first term of the thesis, students must submit a proposal - with project details and significant design component clearly defined - for review and approval by the thesis mentor and chemical engineering senior thesis coordinator (Option Rep). In addition, students must submit the following to the thesis mentor and chemical engineering senior thesis coordinator: a midterm progress report in each term; end-of-term progress reports at the end of the first two terms; and a thesis draft in the third term. A grade will not be assigned prior to completion of the thesis, which normally takes three terms. A P grade will be given for the first two terms and then changed to the appropriate letter grade at the end of the course.


Examination of the chemistry of the interstellar medium, of protostellar nebulae, and of primitive solar-system objects with a view toward establishing the relationship of the chemical evolution of atoms in the interstellar radiation field to complex molecules and aggregates in the early solar system that may contribute to habitability. Emphasis will be placed on identifying the physical conditions in various objects, timescales for physical and chemical change, chemical processes leading to change, observational constraints, and various models that attempt to describe the chemical state and history of cosmological objects in general and the early solar system in particular. Given in alternate years; not offered 2022-23.


Student groups complete a one-term, data-science project that addresses an instructor-approved chemical engineering challenge. The project may be an original research idea; related to work by a research group at the Institute; an entry in a relevant national/regional contest; a response to an industry relationship; or other meaningful opportunity. There is no lecture, but students participate in weekly progress updates. A student may not select a project too similar to research completed to fulfill requirements for ChE 80 or ChE 90 abc.


This course will cover selected aspects of the chemistry of aquatic systems. Lectures cover basic principles of physical-organic chemistry relevant to the aquatic environment under realistic conditions. Specific topics covered in Part I include the basic principles of equilibrium chemical and physical processes important natural waters. Topics include: chemical potential, fugacity, phase transfer, acid-base chemistry, metal-ligand substitution chemistry, surface chemistry, octanol-water partitioning, air-water partitioning, partitioning to solid organic matter and biomedia, sorption processes, air-water exchange dynamics, and the kinetics and mechanisms of coupled organic and inorganic redox reactions. Thermodynamics, transport, phase transfer and kinetics are emphasized. 041b061a72


グループについて

グループへようこそ!他のメンバーと交流したり、最新情報をチェックしたり、動画をシェアすることもできます。
bottom of page