Properties of Poly(B-amino Ester)s

Properties of Poly(B-amino Ester)s The poly(b-amino ester)s, a class of biodegradable cationic polymers, were firstly  prepared by Chiellini in 198340. These polymers were based on poly(amidoamine)s  developed in 1970 by Ferruti41, that contain tertiary amines in their backbones and  can be synthesized by a simple Michael addition reaction of bifunctional amines  and bisacrylamides. However, the interest over the use of poly(b-amino ester)s rised  significantly after its use as transfection reagent at Langer Lab in 200042. The development  of poly(b-amino ester)s emerged by the need to develop a cationic polymer  for gene delivery with high transfection efficiency and long-term biocompatibility  including hydrolyzable moieties easily degradable into non-toxic small molecule  byproducts. The synthesis of this polymer can easily be accomplished: without  necessity of independent preparation of specialized monomers; the use of stoichiometric  amounts of expensive coupling reagents, or amine protecti on strategies prior  to polymerization42. The main general objective of the work of mentioned research  group was to develop a polymer-based non-viral vector more efficient and less cytotoxic  than other cationic polymers used at that time for this purpose (such as,  polyethylenimine (PEI) or poly(L-lysine) (PLL)). In fact, poly(b-amino ester) approach exhibited a particularly attractive basis for  the development of new polymer-based transfection vectors for several reasons: the  polymers contain the required amines (positive charges to complex genetic material);  readily degradable linkages (by hydrolysis of ester bonds in the polymer backbones  may increase the biodegradability and biocompatibility); and multiple analogues  could be synthesized directly from compounds commercially available (easy and inexpensive  synthesis) allowing to tune polymer properties (like buffering capacity)42. Besides being used as transfection vector, PbAEs has been also applied in others  biomedical areas, such as delivery systems for drugs43;44 or proteins45;46, magnetic  resonance imaging agents47;48, or as scaffold for tissue engineering49;50. Synthesis and main physicochemical properties of poly(b-amino ester)s The poly(b-amino ester)s are easily synthesized by the conjugate addition of a primary  amine or bis(secondary amine) and a diacrylate, in a one-step reaction without  any side product that need be removed through further purification steps. It can be  prepared without solvents, catalysts, or complex protecting group strategies42;51. Depending on the ratio of monomers during the synthesis, poly(b-amino ester)s  can be tailored to have either amine- or diacrylate-terminated chains. An excess of  either diacrylate or amine monomer results in a prevalence of acrylate- or amineterminated  poly(b-amino ester)s, respectively52;53. The synthesis is performed either neat (solvent free) or in anhydrous organic  solvents to mitigate hydrolytic degradation during synthesis42;54. Normally, experiments  using solvents occur at lower temperature and over long periods of time  compared to solvent-free formulations. Table 1.3 summarizes the main reactions for  the synthesis of PbAE and the obtained properties such as molecular weight, polydispersity  index (à ), solvent solubility or yield. The most common solvents used are dimethylsulfoxide (DMSO), chloroform  (CHCl3), or dichloromethane (CH2Cl2)57. However, others solvents have also been  used, such as methanol, N,N-dimethylformamide (DMF) or N,N-dimethylacetamide  (DMA)59;61–63. The solvent used has influence on the final molecular weight of the  PbAE. For example, the use of CH2Cl2 typically yields higher molecular weight  polymer compared to THF42. On the other hand, solvent-free polymerizations maximize monomer concentrations,  thus favoring the intermolecular addition over intramolecular cyclization reaction64. The absence of solvent also allows rising temperature resulting in a higher  reaction rate and a lower viscosity of the reacting mixture, assisting to compensate  the higher viscosity found on the solvent-free systems. The combination between  increased monomer concentration and reaction temperature resulting in a reduction  in the reaction time64. The solvent-free reactions also allows the generation of higher  molecular weight polymers, besides increasing the reaction rate and obviating the  solvent removal step53;64. After polymerization, PbAE can be precipitated, normally in cold diethyl ether,  hexane42, ether65 or ethyl ether58 and/or then dried under vacuum57;65. Frequently, PbAEs are immediately used or stored in the cold conditions (4 _C52;66;67, 0 _C62, or  -20 _C68–70). Some PbAEs should be also kept airproof due to its strong moisture  absorption ability and easy degradation71. Concerning to the biodegradation and biocompatibility, PbAEs have been shown  generally to possess low cytotoxicity and good biocompatibility42;52;61;55;72. Different  studies have suggested that PbAEs are significantly less toxic than currently available  cationic polymers, such as, PEI and PLL51;64. Nevertheless, the increase of the  number of carbons in the backbone or side chain is associated to the increase of the  cytotoxicity73. PbAE degrade under physiological conditions via hydrolysis of their  backbone ester bonds to yield small molecular weight b-amino acids biologically  inert derivatives42;51;55;74. Some results revealed that the degradation rate of poly(b  amino ester)s was highly dependent on the hydrophilicity of the polymer, i.e., the  more hydrophilic the polymer is, the faster the degradation occurs75;76. In Table 1.4 are summarized the main characteristic of PbAEs which make them  a promising polymeric non-viral vector for gene delivery. Combinatorial libraries a fast and efficient way to evaluate different poly(bamino ester)s A fast and efficient way to study the relationships between structure and function  in particular material that could be prepared with different reagents is using combinatorial  libraries. Due to promising preliminar results of PbAEs as non-viral vectors,  Langer research group reported a parallel approach for the synthesis of hundreds of  PbAEs with different structures and the application of these libraries to a rapid and  high throughput identification of new transfection reagents and structure-function trends. For this purpose, major contributions have been reported52;53;57;66;67;72;75;77;78  not only exploring the possible structure/function relationships, but also imposing  an assortment of monomers (amines were denoted by numbers and acrylates by latin  alphabet letters) used in order to facilitate cataloging of different PbAEs (Table 1.5  and Tables A.1 and A.2 (Appendix A)). The first initial library screening was synthesized in 2001 by Lynn51. 140 Different  PbAEs from 7 diacrylates and 20 amines were prepared with molecular weights  between 2,000 and 50,000 g.mol-1. From this, polymers C93 (Mw = 3180 g.mol-1) and  G28 (Mw = 9170 g.mol-1) revealing transfection levels 4-8 times higher than control  experiments employing PEI. At same time, it was observed that for transfection efficiency,  high molecular weight was not an important parameter. This work was then  completed in 2003 by Akinc57, where biophysical properties and the ability of each  polymer/DNA complex to overcome important cellular barriers to gene deliver were investigated. As previous experiments, complexes formed from polymers C93 and  G28, revealed higher levels of internalization compared to †naked† DNA, displaying  18- and 32-fold more internalization, respectively. In contrast, the majority of the  polyplexes were found to be uptake-limited. Regarding d iameter and zeta potential,  out of 10 polymer/DNA complexes with the highest internalization rates, all  had diameters lower than 250 nm and 9 had positive zeta potentials. By measuring  the pH environment of delivered DNA through fluorescence-based flow cytometry  protocol using plasmid DNA covalently labeled with fluorescein (pH sensitive) and  Cy5 (pH insensitive) it was possible to investigate the lysosomal trafficking of the  polyplexes. The results demonstrated that complexes based on polymers C93 and  G28 were found to have near neutral pH measurements, indicating that they were  able to avoid acidic lysosomal trafficking. In the same year, Akinc64 studied the  effect of polymer molecular weight, polymer chain end-group, and polymer/DNA  ratios on in vitro gene delivery. For this purpose, 12 different structures were synthesized  based only in two different PbAE (C28 prepared from 1,4-butanediol diacrylate  and 1-aminobutanol and E28 prepared from 1,6 -hexanediol diacrylate and  1-aminobutanol) (Figure 1.6.) These structures were synthesized by varying amine/diacrylate stoichiometric ratios, resulting in PbAEs with either acrylate or amine end-groups and with molecular  weights ranging from 3,350 to 18,000 g.mol-1. Polymers were then tested, using high  throughput methods, at nine different polymer/DNA ratios between 10/1 (w/w)  and 150/1 (w/w). Concerning terminal groups, it was found that amino-terminated  polymers transfected cells more effectively than acrylate-terminated polymers. In  contrast, none of the acrylate terminated PbAEs mediated appreciable levels of  transfection activity under any of the assessed conditions. These findings suggest that end-chains of PbAE have crucial importance in transfection activity. Concerning  molecular weight effect, highest levels of transfection occurred using the higher  molecular weight samples of both amine-terminated C28 (Mw _13100 g.mol-1 and  E28 (Mw _13400 g.mol-1). Regarding the optimal polymer/DNA ratios for these   polymers, it was observed a markedly difference, 150/1 (w/w) for C28 and 30/1 for  E28. These results highlighted the importance of polymer molecular weight, polymer/DNA ratio, and the chain end-groups in gene transfection activity. Moreover, it  has found the fact that two similar polymer structures, differing only by two carbons  in the repeating unit, have different optimal transfection parameters emphasizing  the usefulness of library screening to perform these optimizations for each unique  polymer structure. Meanwhile, in 2003, Anderson52 described, for the first time,  a high-throughput and semi-automated methodology using fluid-handling systems  for the synthesis and screening of a library of PbAEs to be used as gene carrier. A crucial feature of these methods was that all process of synthesis, storage, and  cell-based assays were performed without removing solvent (DMSO). By using these  methods, it was possible to synthesize a library of 2350 structurally unique, degradable  and cationic polymers in a single day and then test those as transfection reagent  at a rate of _1000 per day. Among PbAEs tested, it was identified 46 polymers  that transfect in COS-7 as good as or better than PEI. The common characteristic  among them was the use of a hydrophobic diacrylate monomer. Moreover, in the  hit structures mono- or dialcohol side groups and linear, bis(secondary amines) are  over represented. From data obtained from this library, Anderson67, in 2004, continued  his study developing a new polymer library of >500 PbAE using monomers  that led higher transfection efficiency in the previous studies and optimizing their  polymerization conditions. The top performing polyplexes were asses sed by using  an in vitro high-throughput transfection efficiency and cytotoxicity assays at different N/P ratios. As previously observed, the most promising polymers are based on  hydrophobic acrylates and amines with alcohol groups. Among those, C32 stood  out due to higher transfection activity with no associated cytotoxicity. The efficiency  to deliver DNA was evaluated in mice after intra-tumoral (i.t.) and intra-muscular  (i.m.) injection. The results revealed important differences. While by i.t injection  C32 delivered DNA 4-fold better than jetPEI R , a commercial polymeric non-viral  vector, by i.m. administration transfection was rarely observed. C32 was then assessed  for DNA construct encoding the DT-A (DT-A DNA) deliver to cells in culture  and to xenografts derived from androgen-sensitive human prostate adenocarcinoma  cells (LNCaP). Results showed that DT-A DNA was successfully delivered and the  protein expressed in tumor cells in culture. In hu man xenografts, the growth was  suppressed in 40% of treated tumors. The fact of C32 is non-toxic and it is able to  transfect efficiently tumors locally and transfects healthy muscle poorly turned it as  a promising carrier for the local treatment of cancer. From here, a panoply of results based in PbAE combinatorial library appeared. In  2005, Anderson53, prepared a new library of 486 second-generation PbAE based on  polymers with 70 different primary structures and with different molecular weights. These 70 polymers were synthesized using monomers previously identified as common  to effective gene delivery polymers. This library was then characterized by  molecular weight of polymers, particle size, surface charge, optimal polymer/DNA  ratio and transfection efficiency in COS-7 of polymer/DNA complexes. Results  showed that from 70 polymers with primary structures, 20 possess transfection activities  as good as or better than Lipofectamine R 2000, one of the most effective commercially  available lipid reagents. Results also revealed that, in general, the most  effective polymers/DNA complexes had In 2006, Green79, synthesized, on a larger scale and at a range of molecular  weights, the top 486 of 2350 PbAEs previously assessed52 and studied their ability to  deliver DNA. These PbAEs were tested, firstly, on the basis of transfection efficacy in  COS-7 cells in serum-free conditions, and then, the 11 of the best-performing PbAEs  structures were further analyzed. The transfection conditions were optimized in human  umbilical vein endothelial cells (HUVECs) in the presence of serum. In this  study, the influence of the factors like polymer structure and molecular weight, and  biophysical properties of the polyplexes (such as, particle size, zeta potential, and  particle stability throughout time) were studied. The results showed that many of  the polyplexes formed have identical biophysical properties in the presence of buffer,  but, when in the presence of serum proteins their biophysical properties changed differentially,  influencing the transfection ac tivity. Concerning to the size, the results  showed that in spite of all vectors condensed DNA into small particles below 150 nm  in buffer, only a few, such as C32, JJ32 and E28, formed small (_200 nm) and stable  particles in serum. C32, JJ32 and E28 revealed also high transfection activity both  in the absence of serum in COS-7 cell line as in the presence of serum in HUVEC  cell line. Moreover, C32 transfected HUVECs in the presence of serum significantly  higher than jetPEI R and Lipofectamine R 2000, the two top commercially available  transfection reagents. The 3 mentioned PbAEs share a nearly identical structure. The acrylate monomers of these polymers, C, JJ, and E, differ by only their carbon  chain lengths (4, 5, and 6 carbons, respectively). Similarly, amines 20, 28, and 32  differ also by only the length of their carbon chain (3, 4, and 5 carbons, respectively). For example, polymers prepared with the same acrylate monomer (C) in which itwas increased the length of the carbons chain of the amine monomer resulted in  an increased transfection efficacy (C32 (5 carbons) > C28 (4 carbons) > C20 (3 carbons))  of these polymers-based polyplexes. Interestingly, this study reinforced C32  as the lead PbAE vector and revealed other potential two, JJ28 and E28, which previously  showedto be poor vectors. On the other hand, C28 and U28, previously  recognized as an efficient transfection reagent, were found to transfect inefficiently  HUVEC in serum. By constructing a new library of end-modified PbAE, the research  was continued78 in order to understand the structure-function relationship  of terminal modification of PbAE in transfection activity. For this purpose, it was  used twelve different amine capping reagents to end-modify C32, D60 and C20. The  choice of these 3 PbAEs was based in their transfection activity: C32, the most effective; D60, an effective transfection reagent with a significantly different structure  from that of C32; and, C20, a poor transfection reagent but with similar structure  to C32 differing only in the length of the amine monomer. The results showed  that some PbAEs-based vectors (C32-103 and C32-117) were able to deliver DNA by  approximately two orders of magnitude higher than unmodified C32, PEI (25,000  g.mol-1) or Lipofectamine R2000, and, at levels comparable to adenovirus at a reasonably  high level of infectivity (multiplicity of infection = 100). Once again, it was  demonstrated that small structural changes influence greatly gene delivery, from biophysical  properties (such as, DNA binding affinity, particle size, intracellular DNA  uptake) until final protein expression. From these 3 polymers assessed, C20 was the  one who transfected cells much less effectively, although it has seen a remarkably  improvement with end-modifications. As expected, C 32-based polyplexes, based on  C32-103 and C32-117, revealed the higher transfection efficiency enhancing cellular  DNA uptake up to five-fold compared to unmodified C32. Interestingly, and in a  general way, terminal modifications of C32 with primary alkyl diamines were more  effective than those with PEG spacers, revealing that a degree of hydrophobicity at  the chain ends is an added value for these polymers. Another interesting fact in terminal  modification of C32 was that at least a three carbon spacer between terminal  amines is necessary to obtain an efficient gene delivery. For example, results showed  that C32-103 transfection efficiency is 130- and 300-fold higher than C32-102 on the  COS-7 and HepG2 cell lines, respectively. As the molecular weight was the same,  this result demonstrated the critical role of the chain ends in transfection activity. In order to better understand the role of the chain ends in transfection efficiency  a new library of end-modified C32 was synthesized by Zugates80 in 2007 using 37  different amine molecules to end-modify the PbAE. In a general way, it was observed  that polymers end-capped with hydrophilic amine end groups containing  hydroxyls or additional amines led to higher transfection efficiency. On the other  hand, terminal-modifications with hydrophobic amines containing alkyl chains or  aromatic rings proved to be much less effective. Concerning to cytotoxicity, terminal  modification with primary monoamine reagents (independently of functional group  extending from the amine, such as aromatic, alkyl, hydroxyl, secondary and tertiary

Ciminal Insanity Essay -- Judicial Criminal System

â€Å"A judge's ruling today that an Irvington babysitter who stabbed her 5-year-old nephew 57 times is not guilty by reason of insanity was followed by screams of agony from the dead child's father.† (Juri, 2009) This woman will be locked up, but in a maximum security psychiatric facility not a prison. Is this just? Is this fair? It may be. What if this woman did not know that the child was what she was stabbing? What if she saw a dog that was attacking her, or maybe she was even farther removed from reality. This is the difficulty with criminal insanity cases. Sometimes, even if the person is mentally ill a murder is a murder; theft is theft. Should criminal insanity be a useable defense in Canadian court systems? Through the history there have been three basic definitions of legal insanity. First was the M'Naghten Rule. This rule stated that a person was only considered legally insane if they were "incapable of appreciating his surroundings"(Montaldo, 2010) due to a mental illness. This is a quite strict definition without much room for special cases. It caused a â€Å"black and white† view of criminal insanity cases. The M'Naghten Rule lasted until the 1950s when in the Durham v. United States case the court ruled that "would not have committed the criminal act but for the existence of a mental disease or defect."(Montaldo, 2010) the Durham method got a lot of criticism because it was very lenient on the definition of criminal insanity so that it almost depended on the judge to decide if the person was to be considered criminally insane or not. To address this problem a third method was created by the American Law Institute and was published as part of the Model Penal Code. The Model Penal Code provided a standardized idea of crimina... ...us reus. Retrieved from http://www.answers.com/topic/actus-reus Burns, K. (2008, May 16). Criminal insanity . Retrieved from http://karisable.com/crmh.htm Dryden-Edwards, MD, R. (2010). Schizophrenia. Retrieved from http://www.medicinenet.com/schizophrenia/page3.htm Farlex, . (2010). Insanity defense. Retrieved from http://legal-dictionary.thefreedictionary.com/Criminal+insanity Findlaw, . (2010). The insanity defense: history and background .. Retrieved from http://criminal.findlaw.com/crimes/more-criminal-topics/insanity-defense/insanity-defense-background.html Juri, C. (2009, January 06). Judge accepts insanity defense from babysitter in irvington child's slaying. Retrieved from http://www.nj.com/news/index.ssf/2009/01/a_judges_ruling_today_that.html Montaldo, C. (2010). The insanity defense. Retrieved from http://crime.about.com/od/issues/a/insanity.htm

Global Inequalities Essay

Global inequality generally means that the total income and wealth is spread out unevenly across the world. Almost half of the work (3 billion people) live on less that $2.50 per day, and the majority of these people love in extremely poor countries. There’s a pattern to show that the least developed countries lie in Africa compared to the rest of the world, however there are multiple reasons for this situation; The Conflict Trap, The Natural Resource Trap, The Landlocked with Bad Neighbours Trap, and The Poor Governance in a Small Country Trap. I will talk about each reason in order according to which i believe are most important. Poor governance in a small country is one of the main reasons as to why we have many global inequalities around the world. This is because a poor, corrupted government try to discourage Transnational Companies to locate in their country in order to avoid any wealth being taken out of their economy. This prevents peoples chances of having a job and earning a regular income for a stable lifestyle. Economic isolation leads to a country being globally isolated, this is difficult as everyone is reliant on their government to bring income, however this can’t happen because TNC’s are discouraged. In addition to this, even if a stable government was to take over, its extremely difficult to regain the economy and takes on average 52 years. The second most important factor i believe, is the landlocked with bad neighbours trap. This is because 38% of the poorest countries are landlocked, with the majority of them being in Africa. This is because if you are a coastal country, then you have the freedom to trade with anyone around the world, however when you are landlocked, you are only able to trade with your begun outing countries. However, some countries such as Switzerland and Austria have managed to cope with the issue, implying that a being landlocked is just a potential contributing factor to being economically unequal. A solution for this is to encourage remittances – so encourage some people to emigrate to earn money then send it back home to family for it then to be spent in their economy. This can slowly help  strengthen the economy. I believe the next most important factor would be the conflict trap. Because feel oped nations have had their civil wars in the past however they have managed to release themselves of the unfortunate cycle, however some of the poorest nations generally get trapped in the violent cycle, and any money generated is instantly spent on weaponry. These poorest countries have a substantial amount of young men, who eventually end up turning to crime and recruit into rebel groups because they have nothing else to do, so they have nothing to lose. There is a huge correlation between education and crime, because these men are less educated, the crime is higher. There is also a further correlation between civil unrest and the wealth of a country, showing that the less wealth a country has, the more civil unrest there is. Finally, the last contributing factor to global inequalities is the raw materials trap. This is when a country only has one type of raw material and are extremely reliant on this source to provide their country’s wealth, so they lack diversity. This is a very risky method because the resources are generally non-renewable and the reliance is so high, meaning that if it fails or runs out then they will be in a poor, failing economic state. They will lose all income and won’t be able to afford any imports from other countries, so they will not be able to provide necessities for their country. In conclusion to this essay, i believe that the poor governance in a small country is the main contributing factor to global inequalities, because i believe that every country has the potential to regain the strength in their economy, but with a corrupt government that generally keep money for themselves.

University of Rhode Island (URI) Admissions Facts

University of Rhode Island (URI) Admissions Facts The University of Rhode Island has an acceptance rate of 73%, making it a generally accessible school. That said, admitted students tend to have grades and standardized test scores that are average or better. The admissions process is holistic, and students will need to submit high school transcripts, scores from the SAT or ACT, a personal essay, and a letter of recommendation. The rigor of your high school curriculum will play a meaningful role, so those AP, IB, and Honors classes can all strengthen your application. If you have any questions, be sure to get in touch with the admissions office at URI. Will you get in? Calculate your chances of getting in with this free tool from Cappex. Admissions Data (2016) University of Rhode Island Acceptance Rate: 73Â  percentGPA, SAT and ACT Graph for URITest Scores: 25th / 75th PercentileSAT Critical Reading: 480 / 580SAT Math: 490 / 590SAT Writing: - / -What these SAT numbers meanSAT score comparison for Rhode IslandAtlantic 10 Conference SAT score comparisonACT Composite: 22 / 27ACT English: 21 / 26ACT Math:Â  21 / 26What these ACT numbers meanACT score comparison for Rhode IslandAtlantic 10 Conference ACT score comparison University of Rhode Island Description Located in Kingston, the University of Rhode Island often ranks highly for both its academic programs and its educational value. For its strengths in the liberal arts and sciences, URI was awarded a chapter of the prestigious Phi Beta Kappa Honor Society. High achieving students should look into the URI Honors Program which offers special academic, advising and housing opportunities. In athletics, the University of Rhode Island Rams compete in the NCAA Division I Atlantic 10 Conference for most sports, with football competing in the Colonial Athletic Association. Enrollment (2016) Total Enrollment: 17,822Â  (14,812 undergraduates)Gender Breakdown: 44Â  percent Male / 56 percent Female84 percent Full-time Costs (2016-17) Tuition and Fees: $12,884 (in-state); $28,874 (out-of-state)Books: $1,200 (why so much?)Room and Board: $12,278Other Expenses: $2,043Total Cost: $28,405 (in-state); $44,395 (out-of-state) University of Rhode Island Financial Aid (2015-16) Percentage of New Students Receiving Aid: 93 percentPercentage of New Students Receiving Types of AidGrants: 84 percentLoans: 81 percentAverage Amount of AidGrants: $10,680Loans: $6,408 Academic Programs Most Popular Majors: Accounting, Business Administration, Communication Studies, English, Human Development and Family Studies, Nursing, PsychologyWhat major is right for you? Sign up to take the free My Careers and Majors Quiz at Cappex. Graduation and Retention Rates First Year Student Retention (full-time students): 83Â  percent4-Year Graduation Rate: 42 percent6-Year Graduation Rate: 63 percent Intercollegiate Athletic Programs Mens Sports: Football, Baseball, Golf, Soccer, Basketball, Cross Country, Track and FieldWomens Sports: Softball, Tennis, Volleyball, Basketball, Cross Country, Rowing, Soccer, Track and Field If You Like URI, You May Also Like These Schools University of Connecticut: Profile | GPA-SAT-ACT GraphProvidence College: Profile | GPA-SAT-ACT GraphUniversity of Delaware: Profile | GPA-SAT-ACT GraphBoston University: Profile | GPA-SAT-ACT GraphSyracuse University: Profile | GPA-SAT-ACT GraphSacred Heart University: Profile | GPA-SAT-ACT GraphUniversity of New Haven: Profile | GPA-SAT-ACT GraphBrown University: Profile | GPA-SAT-ACT GraphQuinnipiac University: Profile | GPA-SAT-ACT GraphRhode Island College: ProfileRoger Williams University: Profile | GPA-SAT-ACT GraphNortheastern University: Profile | GPA-SAT-ACT Graph Data Source: National Center for Educational Statistics

Complexometric Determination of Water Hardness Essays

Complexometric Determination of Water Hardness Essays Complexometric Determination of Water Hardness Paper Complexometric Determination of Water Hardness Paper ABSTRACT The average concentration of CaCO3 obtained was 212 ppm, with a standard deviation of 1 ppt. The results indicate that the unk B tap water can be considered as hard water. INTRODUCTION Hard water is due to metal ions (minerals) that are dissolved in the ground water. These minerals include Ca 2+, Mg2+, Fe3+, SO42-, HCO3-. When this water evaporates or boils, the difficult to dissolve metal salts remain as a scaly residue. Hard water inhibits the effectiveness of soap and detergents. Calcium ions typically make the most significant contribution to water hardness. This is why hardness is measured in terms of mg CaCO3/L of solution. Hardness is also reported in units of parts per million (ppm). Water with a hardness value of 60 ppm is considered â€Å"soft† and water with 200 ppm is considered â€Å"hard. † The purpose of this lab was to determine the water hardness of a sample of unk B tap water. The disodium salt of EDTA was used to determine the concentration of M 2+ metal ion impurities in hard water by a complexometirc titration. EDTA is a versatile chelating agent. A chelating agent is a substance whose molecules can form several bonds to a single metal ion. Chelating agents are multi-dentate ligands. EDTA acts as a chelating agent because each nitrogen and one oxygen from each of the four carboxylic acid groups has an electron pair to , donate (ligand- a substance that binds with a metal ion to form a complex ion) to a metal ion center, making EDTA a hexadentate ligand which forms an octahedral complex. An indicator, Eriochrome Black T enables the detection of when the EDTA has completely chelated the metal impurities. In the presence of a metal cation, Eriochrome Black T forms a pink complex. H2In- represents the anion of the free, solvated indicator, and M2+ represents Mg2+ or Ca2+. H2In-3 (aq) + M2+ (aq) MIn- (aq) + 2H+ (aq) Blue pink As you add EDTA solution from a buret, the metal ions preferentially complex to the EDTA, leaving the indicator solvated: EDTA (aq) + MIn- (aq) + 2H+ (aq) ? H2In- (aq) + MEDTA (aq) pink blue A color change from pink to violet to blue indicates the titration endpoint. Adding an ammonia/ammonium chloride buffer (pH 10) to the mixture prior to titration ensures that the calcium metal ions remain in solution and that the indicator works correctly. Proteins drop off and now chelates with calcium and forms a tetrahedral complex. EXPERIMENTAL First, a 500mL 0. 004M EDTA solution was prepared by weighing out 0. 7232g of Na2EDTA and dissolving it in 500 mL of deionized water. A standard calcium solution was prepared in order to standardize the Na2EDTA solution used in the titration of the unk B water sample with 1. 000g CaCO3/L solution. 3 mL of ammonia/ammonium chloride buffer (pH 10) was added under the fume hood. The ammonia buffer is an inhalation irritant. This solution was stirred for 30 seconds. drops of Eriochrome Black T indicator were added just before titrating. The titration was completed 3 times. The average molarity of disodium EDTA and precision were determined. Table 1. standardization titration EDTA RunVol (mL) 124. 20 224. 00 324. 10 Because EDTA chelates Ca2+ ions in a one-to-one molar ratio: [Na2EDTA] = 10. 00 mL CaCO3 soln x1. 000g CaCO3 x 1 mol CaCO3 x 1 mol Na2EDTA = 0. 004128 24. 20 mL Na2EDTA soln 1L CaCO3s oln 100. 1gCaCO3 1mol CaCO3 0. 004128 + 0. 004163 + 0. 004145 /3 = Average Molarity = 0. 004145M #1 # 2 #3 Estimated Precision(ppt)= |sum of absolute deviation|/3 x 1000 (ppt) [Na2EDTA] mean 1. 7 x 10-5 + 1. 8 x 10-5 + 0/3 = 1. 17 x 10-5/3 x 1000 = 1(ppt) #1 #2 #3 (0. 004145M) Next, an unk water sample – B was titrated with the standardized disodium EDTA solution. 25 mL of the unk B water sample was combined with 20 mL of deionized water. 3 mL of ammonia/ammonium chloride buffer (pH 10) was added and stirred for 30 seconds. Just prior to titrating, 4 drops of Eriochrome Black T indicator was added to the solution and stirred for 30 seconds. The titration was conducted 3 times. The hardness (mg CaCO3/L) of the prepared unk B water sample for each titration was calculated. The average hardness and precision from the three trials were then determined. Table 2. Titration of Unknown water sample B Unknown water sample B RunVol (mL) 112. 75 mL 212. 80 mL 312. 70 mL Water Hardness (ppm) = mg CaCO3 x 1000 = V mL Na2EDTA soln x mol Na2EDTA x 1 mol CaCO3 x 100. 1g CaCO3 1 L CaCO3 soln 25. 00 mL CaCo3 soln L Na2EDTA soln 1mol Na2EDTA 1 mol CaCO3 Run 1 = 210. 7 (ppm) Run 2 = 213. (ppm) Run 3 = 210. 8 (ppm) Average ppm = 212 (ppm) Precision = 2 sum of deviation in hardness (0. 9 + 1. 8 = 0. 8)/3 x 1000 (3) (211. 6 ppm) CONCLUSION The results show an average 212 ppm, with a standard deviation on 1 ppt. General guideline for water hardness classification are 0-60 mg/L of CaCO3 are classified as soft while water with more than 200 mg/L of CaCO3 are classified as hard. Based on the data gathered and calculated, it can be concluded that the unk B water sample is considered hard water. This is within allowable range for the City of Tempe, where the range for hardness is 150 -400 ppm with an average of 168 ppm. The unknown B water sample to slightly higher than the City of Tempe average. Some area of experimental error that may have deviated the obtained values from the â€Å"real† value would be the preparation of the standard solution due to contamination. Inaccurate measurements of reagents would also be a factor. Another possibility would be unsuccessful mixing of standard solution or not titrating the solution within the allotted timeframe.

Marketing Mix for U.S.A car market Chery Cars China Essay - 6

Marketing Mix for U.S.A car market Chery Cars China - Essay Example The Isdera Company should also go for standardization of its operations. It can be concluded that all the seven elements of the marketing mix are imperative to a successful international business. Founded in 1997, Chery Company is in the automotive industry in China, specializing in manufacture of minivans, and passenger cars (CheryInternational, 2014). Records indicate that this company is the largest exporter of passenger cars in China, a record that it has held since 2003 (AsiaTimes, 2014). The operations of this company are mainly based in China, but it has also extended its operations to other countries such as Argentina, Egypt, and Iran among others. The company’s most recent developments include the joint ventures with Qoror and Tata motors, a move which has led to the increased production of Chey Jaguar and Chery Land rover (CheryInternational, 2014). The USA car buyers and users are a unique lot. While buyers in other countries prefer big and huge vehicles, the USA consumers prefer the smaller sized vehicles (Luxury Daily, 2013). They also prefer vehicles with the latest technology. One rule under which the USA consumers operate is the â€Å"value for money†. They are not afraid to spend large sums of money so long as the product is worth it (Arguea, Hsiao and Taylor, 2006). They also consider their status when buying a car as they are a populace that values elegant appearances. Marketing mix refers to the strategies and activities that an organisation considers to ensure that the needs of its customers are adequately and sufficiently met (Bowman and Gatignon, 2010). There seven elements in this mix include product, place, price, promotions, physical environment, people and process. Each element is a great determinate of the success of a business, especially one that has grown global as Wendooth (2009) notes. In a bid to achieve homogenization, manufacturers have opted to embrace globalization and see the world as one

Final exam Assignment Example | Topics and Well Written Essays - 1250 words

Final exam - Assignment Example 1). Some examples of Quid Pro Quo sexual harassment are asking for sex as a requirement for promotion and an implied statement that someone would be terminated, if the latter do not submit to the supervisor’s sexual advances. As for Hostile Work Environment type of sexual harassment, it happens when an employee experiences unwelcome sexual advances or gender-based behaviors that are adequately severe or persistent enough to hinder the person’s work performance, or to form a threatening, hostile or unpleasant work environment (Department of Justice, 2003, p. 2). Some examples are unwelcome sexual jokes and remarks and making demeaning statements about one’s gender. Employers can make use of several legal defenses. General employer defenses’ to sexual harassment are applicable to both quid pro quo and hostile work environment sexual harassment. They consist of, but are not limited to the following defenses: 1) â€Å"it didn’t happen,† 2) welcom eness, 3) the conduct was not sexual or was not based on sex, 4) the First Amendment; and 5) the â€Å"equal opportunity harasser†Ã¢â‚¬â„¢ (Weitzman, 1999, pp. 29-30). ... mployees who feel that they have experienced or witnessed sexual harassment, they must take advantage of existing internal policies of their organizations, when present, and if not, report to the proper authorities. These employees must report the incident to their supervisor, manager, or other higher offices (Department of Justice, 2003, p. 3). Though not many sexual harassments can have witnesses, testimonies can be attained from people whom the victims have confided to (U.S. Equal Employment Opportunity Commission (EEOC), 1990, p. 7). Witnesses can be those who witnessed the sexual harassment at the workplace, or noticed changes in the victim’s or charged party’s behavior, and their testimonies can be used to charge the person doing the harassment (EEOC, 1990, p. 7). References Department of Justice, State of California. (2003, July 23). Management bulletin: Sexual harassment in the workplace. Retrieved from http://oag.ca.gov/sites/all/files/pdfs/eeo/03-07mc.pdf U.S. Equal Employment Opportunity Commission. (1990). Enforcement guidance: Policy guidance on current issues of sexual harassment. Retrieved from http://www.eeoc.gov/eeoc/publications/upload/currentissues.pdf Weitzman, A.H. (1999). Employer defenses to sexual harassment claims. Duke Journal of Gender Law Policy, 6, 27-59. Retrieved from http://scholarship.law.duke.edu/cgi/viewcontent.cgi?article=1026&context=djglp 2. Americans with Disabilities Act (ADA) The Americans with Disabilities Act (ADA) (P.L. 101-336) is the most sweeping civil rights legislation that seeks to ban discrimination against people with disabilities. Public and private businesses, state and local government agencies, transportation and utilities, and all firms offering public accommodations and services are required to follow this