Madam & Eve

The story takes place in South Africa. The main characters are Madam Eve and her daughter, Thandi. During the apatheid Eve was Madam's slave, since the end they remained good friends. 1. It is the first school day for Thandi a black young girl. Her mother and madam and Madam accompanies her to the entrance of school and say her to enjoy herself. 2. Thandi meets two school young-boy-white. 3. One asks Thandi for what she is here. And the other one adds that this school was a great school until people as Thandi arrives. 4. By far Madam and Eve look at the scene and think Thandi is again a victim of rascisme. 5. Madam querels them, by explaining them that now it is the new South Africa. Where blacks and whites live together and have the same rights. 6. The boys are surprised of reactions of the ladies. Because the problem is not the skin colour of thandi, but the fact whether she is a girl. Cause this school used to an all-boys school. 7. A third black little boy makes his appearance. To show and press on the fact that the blacks are not a problem in this school but the girls yes! Furthermore for them the girls are Yucky !! 8. Madam et Eve Smile 9. But Thandi does not want that they get away like that. Conclusion : To conclude, we can say that this comic strip raises the new problem of this society, the sexism.

the leadership moment essays

the leadership moment essays The Leadership Moment is a collection of "nine true stories of triumph and disaster and their lessons for us all." The stories are familiar: Eugene Kranz and Apollo 13; John Gutfreund and Salomon Brothers; Joshua Lawrence Chamberlain and the Civil War, to name a few. The stories are drawn from the past and present, represent a wide-range of challenges that include both natural and man-made disasters, and illustrate lessons of success and failure. The author, Michael Useem, is the director of the Wharton Schools Center for Leadership and Change Management. He does a superb job of relating the events and definitive moments of each narrative. Events unfold with the right mix of facts and drama to keep the reader interested. Lessons, or implications as Useem calls them, are woven throughout the narratives. Charts and pictures supplement the text where appropriate. The nine stories are sandwiched by an introduction and conclusion. All the implications presented in the book, about 40, are summarized in a final chapter called "A Leader's Guide." The book assumes that much can be learned about leadership by the successes and failures of others. The author's concluding chapter extracts nine leadership principles from the nine leadership moments: know yourself, explain yourself, expect much, gain commitment, build now, prepare yourself, move fast, find yourself, and remain steadfast. The Leadership Moment reads like an adventure novel. Even the books cover, mountain climbers trudging up a foreboding slope, promotes a sense of intrigue and danger. Useem is a great storyteller. His selection of narratives provokes many thoughts about leadership triumphs and disasters. My only real frustrations with the book stem from the implications and the nine leadership principles. The 40 implications that Useem introduces across the nine chapters can overwhelm a reader. Even though he summarizes them in the Leadershi...

Average SAT Scores by State (Most Recent)

Average SAT Scores by State (Most Recent) SAT / ACT Prep Online Guides and Tips More than a million students across the country take the SAT each year. So what do SAT scores by state look like? How do you stack up against other test takers in your state? Finally, what are some interesting state facts- for example, which state has the highest SAT score? The lowest SAT score? The highest rate of participation? It's the battle of the states, SAT edition. Find out your state's average SAT scores and other fun facts in this article! What Is the National Average SAT Score? Before we get into the SAT averages by state, let's quickly go over the SAT scoring system as well as what the overall average SAT score in the US currently is. As you probably know, the SAT is made up of three sections: Reading, Writing and Language (also just called Writing), and Math. The Math section is scored on a scale of 200-800, while the Reading and Writing sections are combined to give you a final Evidence-Based Reading and Writing (EBRW) score on a scale of 200-800. By combining these two sections, we get atotal SAT score rangeof400-1600, with 1600 being a perfect score. Now that we've got this down, let's take a look the national average SAT score. In 2018, the College Board reported the following average SAT scores: Total: 1068 Evidence-Based Reading and Writing (EBRW): 536 Math: 531 As you can see, the average scores for EBRW and Math are quite close. These then add up to get a total SAT average score that's around the halfway point of the total score range (400-1600). But what are the average SAT scores by state? Keep reading to learn some interesting trends and to see the notable top spots held by different states! State SAT Awards We'll start with the states that have won our "State SAT Awards." The categories for these are as follows: Highest SAT Score Highest SAT Score With Over 20% Participation Team Players (100% Participation) Lowest SAT Score Most Variation Between SAT Sections All data below comes from the College Board's 2018 SAT state reports. Highest Score: Minnesota (SAT Score: 1298) Minnesota takes the cake for highest average SAT score with 1298. This is 230 points higher than the national average! But wait- Minnesota also has lower test participation than 78% of the US at 4%. In other words, just 2,464 seniors took the test in 2018. Because more students in Minnesota take the ACT than they do the SAT, Minnesota's high average SAT score likely means that only the most prepared, ambitious high schoolers take the SAT. These students tend to score higher, effectively raising the state's average. But what if we look instead at states with a significant participation rate- that is, a state in which more than 20% of students take the SAT? The winner for that SAT award is ... Highest Score With Over 20% Participation: Arizona (SAT Score: 49, with 29% Participation) Great achievement here! With more than 20,000 students in the class of 2018 taking the SAT here, Arizona is truly outperforming the national average. Team Players (100% Participation): Colorado, Connecticut, Delaware, Idaho, and Michigan In Colorado, Connecticut, Delaware, Idaho, and Michigan, every student took the SAT. This usually means that thesestates require all high school students to take the SATas part of normal high school testing. In addition, four other states- Illinois, Maine, New Hampshire, and Rhode Island- as well as the District of Columbiaoffered the SAT statewide during the 2017-18 school year. But because the testwasn't mandatory for all students in these states for the entire school year, participation rates here are below 100%. The highest participation rate for non-mandatory testing goes to Florida, at 97%. Lowest Score: District of Columbia (SAT Score: 977) Unfortunately, the District of Columbia underperforms the national average by more than 90 points. Also ranking at the bottom are other states with statewide SAT testing (Delaware and Idaho) as well as West Virginia, Puerto Rico, and the US Virgin Islands. From the data, it's reasonable to conclude that statewide testing causes lower scores because it includes all seniors andnot just those planning to apply to college. The lowest SAT score for a non-mandatory state is 1014 in Florida. While Florida is only in the top 18% of the country as far as participation goes (97% participation rate), it's important to point out that this is still a huge number of students, as the population of Florida is so large. In 2018, 147,058 students took the SAT in Florida. This number is much higher than the number of test takers in other states with comparable SAT participation rates, such as Rhode Island (97% participation rate, 10,161 students) and New Hampshire (96% participation rate, 14,834 students). So even though only 97% of students took the SAT in Florida, there's still plenty of room for variation within these nearly 150,000 students' scores. Most Variation Between Sections: Florida (520 Evidence-Based Reading and Writing, 497 Math) With a participation rate of 97%, Florida also has the greatest difference between SAT section scores of all states. On average, Florida students score 29 points higher on Evidence-Based Reading and Writing (EBRW) than they do on Math. Want to learn more about the SAT but tired of reading blog articles? Then you'll love our free, SAT prep livestreams. Designed and led by PrepScholar SAT experts, these live video events are a great resource for students and parents looking to learn more about the SAT and SAT prep. Click on the button below to register for one of our livestreams today! List of All Average State SAT Scores Here are the most recent average SAT scores for all 50 statesas well as the District of Columbia, Puerto Rico, and the US Virgin Islands. Find your area below and see how your SAT score compares with your region's average! State Participation Rate EBRW Math Total Alabama 6% 595 571 66 Alaska 43% 562 544 06 Arizona 29% 577 572 49 Arkansas 5% 592 576 69 California 60% 540 536 1076 Colorado 100% 519 506 1025 Connecticut 100% 535 519 1053 Delaware 100% 505 492 998 District of Columbia 92% 497 480 977 Florida 97% 522 493 1014 Georgia 70% 542 522 1064 Hawaii 56% 550 549 1099 Idaho 100% 508 493 1001 Illinois 99% 513 506 1019 Indiana 67% 546 539 1086 Iowa 3% 634 632 1265 Kansas 4% 633 631 1265 Kentucky 4% 630 618 1248 Louisiana 4% 615 595 1210 Maine 99% 512 501 1013 Maryland 76% 545 535 1080 Massachusetts 80% 562 563 25 Michigan 100% 5 499 10 Minnesota 4% 643 655 1298 Mississippi 3% 630 606 1236 Missouri 4% 633 629 1262 Montana 10% 606 592 1229 Nebraska 3% 629 623 1252 Nevada 23% 574 566 40 New Hampshire 96% 535 528 1063 New Jersey 82% 547 547 1094 New Mexico 16% 552 540 1093 New York 79% 534 534 1068 North Carolina 52% 554 543 1098 North Dakota 2% 640 643 1283 Ohio 18% 552 547 1099 Oklahoma 8% 541 521 1062 Oregon 48% 564 553 17 Pennsylvania 70% 547 539 1086 Puerto Rico - 512 481 993 Rhode Island 97% 513 505 1018 South Carolina 55% 547 523 1070 South Dakota 3% 622 618 1241 Tennessee 6% 624 607 1231 Texas 66% 520 512 1032 Utah 4% 618 612 1230 Vermont 64% 565 554 20 Virgin Islands - 490 445 935 Virginia 68% 567 550 17 Washington 69% 543 538 1082 West Virginia 28% 513 486 999 Wisconsin 3% 641 653 1294 Wyoming 3% 633 635 1257 Source: The College Board What's Next? Confused about SAT scoring? Learn more about how the SAT is scored,and get tips onhow to figure out your SAT goal score based on the schools you're applying to. Wondering what it takes to get a perfect SAT score? I scored a perfect SAT scoreand wrote a detailed guide about what it takes here.Read this to learn all of my best strategies- and to get a 1600 on test day! If you liked this post, make sure youscroll up and subscribe on the right hand sideso you can stay up-to-date with our SAT/ACT articles! Disappointed with your scores? Want to improve your SAT score by 160 points?We've written a guide about the top 5 strategies you must be using to have a shot at improving your score. Download it for free now:

Introduction to economics Assignment Example | Topics and Well Written Essays - 1000 words

Introduction to economics - Assignment Example In this way, economic power is widely dispersed. But in a planned or command economy, resources are publicly owned and economic decisions are made through central economic planning. This is because a central planning board determines major economic decisions. In free market economy, the individual freedom is valued and motivation comes from each agent’s self-interest in maximizing their income through individual decision-making. Buyers can freely choose what goods and services to purchase and at what price while sellers can freely decide what goods and services to produce and in what quantity. As to a planned economy, business firms are owned and controlled by the government, so they produce according to the central planning board’s directives. Free market economy is an economic system in which trading and exchange of goods, services and  information  takes place in a free market (Economywatch.com 2011, par.1). This means that under this economic system, markets are guided by the â€Å"invisible hands†. Law of supply and demand set market prices and all individuals in the economy have full knowledge about it. Individual decisions and preferences are communicated and coordinated through the mechanism of the market system. Government is kept from interfering within the economy as any interference may disturb the efficient functioning of the market system. Their role is limited to private property and making appropriate legal framework in which free market functions. The advocates of planned economy do not agree with this as they see the market as imperfect and therefore they recommend government intervention to correct market failures. Production targets for each firm are set by the central planning board including the amount of resources to be allocated. Even the distribution of output is determined and planned centrally. Both free market economy and planned economy have their advantages and disadvantages. The Great Depression was being blamed to the imperfect market system and inefficient business cycle. So, the United States government tried to intervene in the economy but still the effects of economic recession in 2008 was felt by most of the economies in the world. Because of these, most economies of the world are applying the mixed economic system, mixing the characteristics of a free market economy with a command economy. Real world economies are arrayed between the extremes of free market and planned economy (McConnell and Brue 1993, p.31). The United States economy, for example, leans toward free market system which is basically structured with the principles of economic freedom but the government plays an active role in promoting economic stability and growth, in providing goods and services which are either underproduced or not produced at all by the market system and in modifying the distribution of income. While some command or planned economies before like China and India are now economically successfu l after following the principles of market oriented economy system. This means that the mixed economy is more conducive to efficiency in the use of resources, stability of output and employment and rapid economic growth because even if the government has some level of regulatory control over the markets, the decisions are still left to the buyers and sellers in the

Compare and contrast two developmental approaches to the study of Essay

Compare and contrast two developmental approaches to the study of developmental psychology. You must refer to research and theory in your answer - Essay Example Contrastingly, developmental psychologists who emphasized learning theories, such as Lev Vygotsky, John B. Watson, B.F. Skinner and Albert Bandura focus on the role of environment more than on the part played by biology. The diverse theories are based on different assumptions, but are similar in some respects (Sigelman & Rider, 2006: 49). The two developmental approaches which are chosen for comparison in this paper are those of Erikson (1902-1994) and Piaget (1896-1987). The similarities and differences between their theories will be examined, including the extent to which nature versus nurture play a part. On the nature side of the nature-nurture controversy, the nativist belief is that human development is determined by innate factors such as genetic endowment and brain maturation. On the nurture side, also known as empirism, development is considered as the result of experience and learning. Although there are some biologically based limits on behaviour and cognition, the â€Å"brains are open, dynamic information processors that are receptive to sociocultural influences† (Kitayama & Cohen, 2007: 528). According to Jean Piaget’s theory, the development of intelligence in children progresses through a series of four stages based on age and concurrent biological changes and maturation. This leads to the child demonstrating a higher level of cognitive functioning at each successive stage, as compared to the previous stage (Videbeck, 2007: 61). The stages of development are not universal, since cultural differences exist. However, the mechanisms that underlie cognitive development are considered to be universal (Pressley & McCormick, 2007: 89). 1. The sensorimotor stage: This extends from birth to two years. The child develops a sense of self, differentiated from the environment, and develops the concept of object permanence. That is, a perception of the existence of tangible objects even

How fast-food has a significant impact in Childhood obesity Research Paper

How fast-food has a significant impact in Childhood obesity - Research Paper Example How fast-food has a significant impact in Childhood obesity? Childhood obesity is a serious/major public health concern and it currently getting a great amount of attention because of its wider economic impacts, as well as the long term consequences on children’s overall health, quality of life, academic achievements and productivity as they turn into adults. Fortunately, latest findings point out that the growth in the proportion of children categorized as obese or overweight has finally leveled off. Nevertheless, rates of obesity and overweight still remain high. â€Å"Almost 35% of children aged 6 to 19 years are overweight and roughly 19% are obese†. Taking health into consideration, the effects of obesity among children include coronary heart disease, hypertension, type 2 diabetes, orthopedic abnormalities and respiratory problems. One of the fields of the food industry, which is being held responsible for the prevalence of childhood obesity, is the FAFH – food-away-from-home – sector, in essence, the fast food industry. From the late 70’s till the mid 90’s, the volume of foods consumed away from home went up considerably from 16% to 29%. The eating patterns of children, particularly those in school, have echoed the fast growth of the FAFH industry. In the late 70’s, children obtained roughly 20% of their caloric intake from food FAFH sources. The data obesity surveys conducted from 2003 to 2006 show that food-away-from-home was liable for 35% of children’s caloric intake. A number of surveys have argued that children who take more fast-food have much lower dietary quality are also expected to be obese or overweight. This paper will discuss how fast-food has a significant impact in Childhood obesity. Background Whereas the main motivation of centering on children is the accessibility of geographically explicit information on weight measures for an extremely big sample, children are a significant group to research in their own right. â€Å"Among school aged chi ldren, 6-19 rates of overweight have soared from about 5% in the early 1970s to 16%, in 1999-2002† (Currie et al. 5). These rates are of significant concern provided that children who are obese are most expected to be obese or overweight as grownups and are gradually suffering from illnesses related to overweight when still young. Critics of the fast food sector point to a number of features, which might make fast food less healthy compared to other types of FAFH. These comprise of low time and monetary costs, high calorie levels of signature menu items and large portions. For sure, energy densities for personal food items are normally too high that it would be hard for people consuming them not to go past their normally recommended dietary intakes (Currie et al. 6). A number of consumers might be specifically defenseless. In two randomized practical trials concerning 26 overweight and 28 normal-weight children, Sinclair et al. (2833) contrasted caloric intakes on â€Å"unres tricted fast-food days,† as well as â€Å"no fast-food days.† The researchers found out that overweight children had much higher caloric intakes on â€Å"fast-food days† compared to â€Å"none fast-food days. The main fast food chains are also concerned in aggressive advertising to children. One particular experimental study of children aged three to five years provided them identical pairs of beverages and foods, the only distinction being that some foods were packaged by McDonalds (Robinson et al. 792). Data Sources and Summary Statistics Data for this paper came from three sources: school data and restaurant data. School Data The data on children from this study came from Californian schools from the late 90 and early 2000s up to 2007. The study of mostly 9th graders, which the paper centers on, represents 3.6 million student-year observations. In California, during spring, 9th graders are normally given fitness assessment test,

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