PET flakes extruder

In order to save costs, one is working on the direct use of the PET-flakes, from the treatment of used bottles, with a view to manufacturing an increasing number of polyester intermediates. For the adjustment of the necessary viscosity, besides an efficient drying of the flakes, it is possibly necessary to also reconstitute the viscosity through polycondensation in the melt phase or solid-state polycondensation of the flakes. The latest PET flake conversion processes are applying twin screw extruders, multi screw extruders or multi rotation systems and coincidental vacuum degassing to remove moisture and avoid flake pre-drying.

Acetyl

http://en.wikipedia.org/wiki/Acetyl_group


Acetyl

IUPAC name[hide]

ethanoyl

other names[hide]

Acetyl cation
Acetylium ion

Identifiers
PubChem 644096
SMILES

 [show]

C[C+]=O

Properties
Molecular formula C₂H₃O⁺
Molar mass 43.04 g/mol
Exact mass 43.01839
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references




In organic chemistry, acetyl is a functional group, the acyl with chemical formula COCH₃. It is sometimes abbreviated as Ac (not to be confused with the element actinium). The acetyl group contains a methyl group single-bonded to a carbonyl. The carbonyl center of an acyl radical has one nonbonded electron with which it forms a chemical bond to the remainder R of the molecule. In IUPAC nomenclature, acetyl is called ethanoyl, although this term is rarely heard. The acetyl moiety is a component of many organic compounds, including the neurotransmitter acetylcholine, acetyl-CoA, and the analgesics acetaminophen, and acetylsalicylic acid (better known as aspirin).

Contents [hide] 1 Acetylation 1.1 In nature 1.2 Synthetic organic and pharmaceutical chemistry 2 Pharmacology 3 References 4 See also

[edit] Acetylation

[edit] In nature

The introduction of an acetyl group into a molecule is called acetylation. In biological organisms, acetyl groups are commonly transferred to coenzyme A (CoA) and from acetyl-CoA. Acetyl-CoA is an intermediate both in the biological synthesis and in the breakdown of many organic molecules. In synthetic organic chemistry,
Histones and other proteins are often modified by acetylation. For example, on the DNA level, histone acetylation by acetyltransferases (HATs) causes an expansion of chromatin architecture allowing for genetic transcription to occur. Conversely, removal of the acetyl group by histone deacetylases (HDACs) condenses DNA structure, thereby preventing transcription.^[1]

[edit] Synthetic organic and pharmaceutical chemistry

Acetylation can be achieved using a variety of methods, most commonly by the use of acetic anhydride or acetyl chloride, often in the presence of a tertiary or aromatic amine base. A typical acetylation is the conversion of glycine to acetylglycine:^[2]

H₂NCH₂CO₂H + (CH₃CO)₂O → CH₃C(O)NHCH₂CO₂H + CH₃CO₂H

[edit] Pharmacology

Acetylated organic molecules exhibit increased ability to cross the blood-brain barrier. Acetylation helps a given drug reach the brain more quickly, making the drug's effects more intense and increasing the effectiveness of a given dose. The acetyl group in acetylsalicylic acid (aspirin) enhances its effectiveness relative to the natural anti-inflammatant salicylic acid. Similarly, acetylation converts the natural painkiller morphine into the far more potent heroin (diacetylmorphine).
Most recently, the supplement industry touts acetyl-L-carnitine as being more effective than other preparations of carnitine. Acetylation of resveratrol holds promise as one of the first anti-radiation medicines for human populations.^{[citation needed]}

[edit] References

1. ^ Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISBN 1-57259-153-6.
2. ^ R. M. Herbst and D. Shemin (1943), "Acetylglycine", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV2P0011 ; Coll. Vol. 2: 11 

[edit] See also

• Acetoxy group
• Histone acetylation and deacetylation
• Polyoxymethylene plastic, a.k.a. acetal resin, a thermoplastic

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Fwd: Engines of Creation 2.0

---------- Forwarded message ----------
From: technologiclee <technologic...@gmail.com>
Date: Feb 16, 6:26 am
Subject: Engines of Creation 2.0
To: Open Manufacturing

Engines of Creation 2.0 is available to read online for free, or as
a .pdf download for $0.99

http://www.wowio.com/users/product.asp?BookId=503

Fwd: Metamodern How to study for a career in nanotechnology

---------- Forwarded message ----------
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Date: Tue, Feb 23, 2010 at 7:01 PM
Subject: Metamodern (1 new item)
To: technologiclee@gmail.com

Metamodern (1 new item)

Item 1 (02/24/10 00:02:19 UTC): How to study for a career in nanotechnology

Students often ask me for advice on how to study for a career in nanotechnology, and as you might imagine, providing a good answer is challenging. "Nanotechnology" refers to a notoriously broad range of areas of science and technology, and progress during a student's career will open new areas, and some are yet to be imagined. Choices within this complex and changing field should reflect a student's areas of interest and ability, current background, level of ambition, and willingness to to accept risk — there is a trade-off between pioneering new directions and seeking a secure career path.

Here is an attempt to give a useful answer that takes account of these unknowns. My advice centers on fundamentals, outlining areas of knowledge are are universally important, and offering suggestions for how to approach both specialized choices and learning in general. It includes observations about the future of nanotechnology, the context for future careers.

Learn the fundamentals, and not just in science

The most basic requirement for competence in any physical technology is a broad and solid understanding of the underlying physical sciences. Mathematics is the foundation of this foundation, and basic physics is the next layer. Classical mechanics and electromagnetics are universally important, and the concerns of nanotechnology elevate the importance of thermodynamics, statistical mechanics, and molecular quantum mechanics. A flexible competence in nanotechnology also requires a sound understanding of chemistry and chemical synthesis, of biomolecular structure and function, of intermolecular forces, and of solids and surfaces.

These are important areas of science, but science is not technology. As I've discussed in "The Antiparallel Structures of Science and Engineering", science and engineering are in a deep sense opposites, and must not be confused. Nanotechnology today is a science-intensive area of engineering, largely because the problem of designing a nanostructure is often overshadowed by the problem of finding, by experiment, a way to make it.

This has implications for choosing a course of study.

Engineering and progress in nanotechnology

A measure of progress in nanotechnology is growth of the range of physical systems that can be designed and debugged without extensive experimentation. As a basis for implementing nanoscale digital systems, commercial semiconductor fabrication provides a predictable design domain of this sort, and some areas of structural DNA nanotechnology have become almost as predictable as carpentry.

Computational tools are in a class of their own, an area of immaterial technology that applies to every area of material technology. It's important to understand the capabilities and limitations of these tools, and extending them makes a strategic contribution to progress. Computational tools tools are often the key to transforming reproducible processes and stable structures into reliable operations and building blocks for engineering. Today, better design tools are the key to unlocking the enormous potential of foldamers and self assembly as a basis for implementing complex nanosystems.

Competence in engineering — and understanding how science can support it — requires study of design principles and experience in solving design problems. As with physics, some lessons apply across many domains. Because nanotechnology relies on innovations in macro- and micro-scale equipment, engineering education has immediate and strong relevance. Looking forward, the growth of nanosystems engineering will open increasing opportunities for researchers with backgrounds that provide both the scientific knowledge necessary to understand new nanotechnologies and the engineering problem-solving abilities necessary to exploit them.

Students aiming to pioneer in directions that can open new worlds of nanotechnology should learn enough of both science and engineering to solve crucial problems at the interface between them. The most important of these is the problem of recognizing and developing the means for systematic engineering in new domains, extracting solid toolsets from the flood of novelty-oriented nanoscience.

In considering all of the above, keep in mind that the general direction of nanotechnology leads toward greater precision at the level of nanoscale components, making products of increasing complexity and size, implemented in an increasing range of materials. Molecular-level atomic precision has widespread applications in nanotechnology today, and already provides components with the ultimate precision at the smallest possible length scale. I expect that the road forward will increasingly focus on extending these atomically precise technologies toward greater scale, complexity, and materials quality. I recommend courses of study that prepare for this.

Choosing topics and ways to study them

In both science and engineering, a good methodology for selecting an ideal course of study would be to survey a course catalog and note which classes appear in lists of prerequisites for advanced classes in relevant areas of science and engineering. This indicates areas where it is important to study and master the content.

Courses toward the periphery of this network of prerequisites are good candidates for a different mode of study, a mode aimed at understanding the problems an area addresses, the methods used to solve them, and how those problems and methods fit in with the rest of science and technology. I discuss this mode of study in "How to Learn About Everything". It builds knowledge of a kind that can help a student choose topics that call for deeper, focused learning, and it can later help greatly in practical work — scientists and engineers with broader knowledge will see more opportunities and encounter fewer unanticipated problems. These advantages mean fewer days (months, years) lost and greater strides forward.

Choosing institutions

Beyond topics of study, I'm also asked to recommend universities and programs. It's difficult to give a specific answer, because a good choice depends on all of the above, and because for each of many areas of science and technology, there are many possible institutions, programs, and research groups. I can only advise that students facing this decision first consider their objectives, and then to look for institutions and people able to help them get there. In particular, universities must either offer a degree program that fits, or provide the flexibility to make one. I found a home in MIT's Interdisciplinary Science Program (which I can't recommend, because it no longer exists).

In undergraduate studies, the general breadth, orientation, and quality of a school is more important than any focused undergraduate program that it is likely to have.

Early involvement in research of almost any kind has a special value: It can provide knowledge of kinds that can't be learned from reading, from classes, or even from lab courses. Pay special attention to research that studies atomically precise structures of significant size and complexity. If that research has an engineering component — designing and making things — so much the better.

---

See also:

• How to Learn About Everything
• How to Understand Everything (and Why)
• The Antiparallel Structures of Science and Engineering

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Fwd: Metamodern Chemists deserve more credit: Atoms, Einstein, and the Matthew Effect

---------- Forwarded message ----------
From: Newsfeed to Email Gateway <emlynoregan@gmail.com>
Date: Wed, Feb 17, 2010 at 7:33 PM
Subject: Metamodern (1 new item)
To: technologiclee@gmail.com

Metamodern (1 new item)

Item 1 (02/17/10 23:41:52 UTC): Chemists deserve more credit: Atoms, Einstein, and the Matthew Effect

Johann Josef Loschmidt
Chemist, atomic scientist

Chemists understood the atomic structure of molecules in the 1800s, yet many say that Einstein established the existence of atoms in a paper on Brownian motion, "Die von der Molekularkinetischen Theorie der Wärme Gefordete Bewegung von in ruhenden Flüssigkeiten Suspendierten Teilchen", published in 1905.

This is perverse, and has seemed strange to me ever since I began reading the history of organic chemistry. Chemists often don't get the credit they deserve, and this provides an outstanding example.

For years, I've read statements like this:

[Einstein] offered an experimental test for the theory of heat and proof of the existence of atoms….
["The Hundredth Anniversary of Einstein's Annus Mirabilis"]

Perhaps this was so for physicists in thrall (or opposition) to the philosophical ideas of another physicist, Ernst Mach; he had odd convictions about the relationship between primate eyes and physical reality, and denied the reality of invisible atoms.

Confusion among physicists, however, gives reason for more (not less!) respect for the chemists who had gotten the facts right long before, and in more detail: that matter consists of atoms of distinct chemical elements, that the atoms of different elements have specific ratios of mass, and that molecules consist not only of groups of atoms, but of atoms linked by bonds ("Verwandtschaftseinheiten") to form specific structures.

When say "more detail", I mean a lot more detail than merely inferring that atoms exist. For example, organic chemists had deduced that carbon atoms form four bonds, typically (but not always) directed tetrahedrally, and that the resulting molecules can as a consequence have left- and right-handed forms.

The chemists' understanding of bonding had many non-trivial consequences. For example, it made the atomic structure of benzene a problem, and made a six-membered ring of atoms with alternating single and double bonds a solution to that problem. Data regarding chemical derivatives of benzene indicated a further problem, leading to the inference that the six bonds are equivalent. Decades later, quantum mechanics provided the explanation.

The evidence for these detailed and interwoven facts about atoms included a range of properties of gases, the compositions of compounds, the symmetric and asymmetric shapes of crystals, the rotation of polarized light, and the specific numbers of chemically distinct forms of molecules with related structures and identical numbers of atoms.

And chemists not only understood many facts about atoms, they understood how to make new molecular structures, pioneering the subtle methods of organic synthesis that are today an integral part of the leading edge of atomically precise nanotechnology.

All this atom-based knowledge and capability was in place, as I said, before 1900, courtesy of chemical research by scientists including Dalton, van 't Hoff, Kekulé, and Pasteur.

But was it really knowledge?

By "knowledge", I don't mean to imply that universal consensus had been achieved at the time, or that knowledge can ever be philosphically and absolutely certain, but I think the term fits:

A substantial community of scientists had a body of theory that explained a wide range of phenomena, including the many facets of the kinetic theory of gases and a host of chemical transformations, and more. That community of scientists grew, and progressively elaborated this body of atom-based theory and technology to up to the present day, and it was confirmed, explained, and extended by physics along the way.

Should we deny that this constituted knowledge, brush it all aside, and credit 20th century physics with establishing that atoms even exist? As I said: perverse.

But what about quantitative knowledge?

There is a more modest claim for Einstein's 1905 paper:

…the bridge between the microscopic and macroscopic world was built
by A. Einstein: his fundamental result expresses a macroscopic quantity — the coefficient of diffusion — in terms of microscopic data (elementary jumps of atoms or molecules).
["One and a Half Centuries of Diffusion: Fick, Einstein, Before and Beyond"]

This claim for the primacy of physics also seem dubious. A German chemist, Johann Josef Loschmidt, had already used macroscopic data to deduce the size of molecules in a gas. He built this quantitative bridge in a paper, "Zur Grösse der Luftmoleküle", published in 1865.

---

I had overlooked Loschmidt's accomplishment before today. I knew of Einstein's though, and of a phenomenon that the sociologists of science call the Matthew Effect.

---

See also:

• A Map of Science
• How to Learn About Everything

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