mihai barbu
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About
Bachelor Degree: Mathematics/ Civil Engineering/Ecology (19952000) University UTCB PhD in ChemistryEcology of building materials Teaching positions(grade 2,grade 1) 2005present I have tutored students ranging from Grades 9 to 12, in various subjects, notably mathematics
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Answered a Question in Science
There are 46 chromosomes in human somatic cells, which are called diploid cells (2n = 46). Gametic cells or sexual cells, are the haploid cells with a total of 23 chromosomes (n = 23). Of the 46... 
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Osmosis is a natural process of balancing the concentration of two waterbased solutions. Osmosis happens at the molecular level. There osmosis processes are classified as it follows: forward... 
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Iron is a mineral that carries oxygen from the lungs. Iron deficiency affects seriously the health. The human body contains about 4 grams of iron. Iron is found in every human cell and it is... 
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In aqueous solution, sulphur dioxide is combined in small proportions with water, creating sulphurous acid, which is a weak acid. The chemical reaction that describes the formation... 
Answered a Question in Science
The human brain is the most complex part of our body. All the movements of human body are initiated by human brain. The human behaviour is controlled by brain. The human senses are interpreted by... 
Answered a Question in Math
If we are going to perform multiplication operation, then we need to remember that multiplication means repeated addition. For example, 5x4 (read five times four) is equal to 20. So, all we have... 
Answered a Question in Science
Cytosol may be defined as the part of cell that remains after cytoskeletal components, membrane and organelles have been removed. Cytosol is often confounded with cytoplasm, which is the fluid that... 
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Mutation is a process that randomly modifies a DNA sequence. DNA modification is not always repaired by the cell and it may be passed down to the next generation. Mutation gives rise to different... 
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Decomposition is the process by which organic materials are broken down into molecules. Most organic matter in terrestrial ecosystems is broken down by decomposers found in soil and trash.... 
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There are two types of respiration: anaerobic, which does not require oxygen, and aerobic, which requires oxygen. The energy released by respiration is used by living organisms for their life... 
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Hybridization occurs when atomic orbitals blend to form new atomic orbitals. Covalent bonds form when the atomic orbitals of two atoms overlap. According to VSEPR theory, `BeCl_2` has a linear... 
Answered a Question in Science
The figure is not visible. Consider the problem data: `a, mu_k` The coefficient of kinetic friction is `mu_k = (f_k)/n` Substitute 0.3 for `mu_k => 0.3 = (f_k)/n => f_k = 0.3*n` Applying... 
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There are two categories of atomic bonds: covalent bonds, ionic bonds. A metal and a nonmeal form an ionic bond. The nonmetal attracts the electrons from the metal very easily. The ionic bond is... 
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Normal household products, milk, vinegar, baking soda, laundry detergent, water, can be used to create endothermic, exothermic, precipitate or gas producing reactions. Sodium acetate can be... 
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Genetic code is a set of biochemical instructions by which living cells translate information encrypted in DNA or RNA sequences into amino acids sequences. The genetic code contains sequence of... 
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The vertical columns of periodic table are called groups. The elements in a group have the same number of electrons in the outer shell. The chemical bonds with other elements involve the electrons... 
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Nano chemicals are materials that are manufactured at a scale that is 10 thousand times smaller than the size of human hair. Nano chemicals are developed to bring forth increased characteristics,... 
Answered a Question in Math
If we find hard to memorize formulas, we can deal with this integral in this way: `int_0^(pi/6) (2cos^3x  cosx)dx = int_0^(pi/6) (cos^3x + cos^3x  cosx  cos x + cos x)dx` Let's see... 
Answered a Question in Math
We going to calculate this limit just putting the value of the limit in place of x: `lim(x>2) (x^38)/(x2) = (88)/(22) =>` `lim(x>2) (x^38)/(x2) = 0/0` The limit didn't work... 
Answered a Question in Math
Put z=0 in elliptic paraboloid equation: `4 – x^2 –(1/4)y^2 = 0` ( i have assumed that `1/4` is coefficient) `16  4x^2  y^2 = 0` Find limits of integration letting first y = 0:... 
Answered a Question in Math
We'll make use of theorem of limits: `lim(x>1,y>2)f(x,y)=f(1,2)` Calculate `lim(x>1,y>2)f(x,y), ` so plug in 1 for x and 2 for y:... 
Answered a Question in Science
The word magnitude describes the brightness of a celestial body and the value of magnitude is inverse proportional to the degree of brightness. Take as example the magnitude of 1 of a... 
Answered a Question in Math
I will start with the final form of equation you must arrive at. Take a look at this equation, get used to it and then we will understand together what we must do to reach to this form: `N(r  r_0)... 
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We must bring into our attention the chemical formula of hydrazine, N2H4. The products that come out from decomposition reaction of hydrazine are nitrogen,hydrogen and ammonia. The decomposition... 
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All inorganic compounds have the property that they do contain chemical elements other than carbon. For example, water is an inorganic compound. Other inorganic compounds are all salts that... 
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By definition, the same current liberates masses of different substances that are proportional to the equivalent masses. Therefore, we must determine the equivalent masse of copper, oxygen... 
Answered a Question in Math
We can start focus on constraint `x^2  3xy  10y^2 = 0` and we can divide the constraint by `y^2` : `(x^2)/(y^2)  (3xy)/(y^2)  (10y^2)/(y^2) = 0` Some simplifications are required:... 
Answered a Question in Math
The intersection between a line and a curve can be found by solving the system of equations of line and curve. Put k = 8 and determine the equation of line: `2y+x = 8` Take out x from this... 
Answered a Question in Math
int (25cos x)/(3cos x+4sin x+5)dx + int (15)/(3cos x+4sin x+5)dx The only useful method of integration right now seems to be substitution `tan (x/2) = y` and identities `sin x =... 
Answered a Question in Chemistry
There exists several characteristics that make the difference between a mixture and a compound. A mixture can contain components in any proportions while a compound contains components in fixed... 
Answered a Question in Math
All polynomial limits we want to solve start with the simple verification: is or isn't an indeterminate form? Please, start the verification by plugging oo in place of x, the same as we do... 
Answered a Question in Math
I will solve the logarithmic equation creating matching bases to the left and to he right of equal. To the left side tells us what is the base of logarithm, so I will create the logarithm in base 4...