Describes and discusses the use of theoretical models as an alternative to experiment in making accurate predictions of chemical phenomena. Addresses the formulation of theoretical molecular orbital models starting from quantum mechanics, and compares them to experimental results. Draws on a series of models that have already received widespread application and are available for new applications. A new and powerful research tool for the practicing experimental chemist.

AB INITIO Molecular Orbital Theory

Publisher Summary This review is concerned with the neglected class of inorganic compounds, which contain ions of the same element in two different formal states of oxidation. Although the number of references cited in our review show that many individual examples of this class have been studied, yet they have very rarely been treated as a class, and there has never before, to our knowledge, been a systematic attempt to classify their properties in terms of their electronic and molecular structures. In the past, systems containing an element in two different states of oxidation have gone by various names, the terms “mixed valence,” nonintegral valence,” “mixed oxidation,” “oscillating valency,” and “controlled valency” being used interchangeably. Actually, none of these is completely accurate or all-embracing, but in our hope to avoid the introduction of yet another definition, we have somewhat arbitrarily adopted the phrase “mixed valence” for the description of these systems. The concept of resonance among various valence bond structures is one of the cornerstones of modern organic chemistry.

Mixed Valence Chemistry-A Survey and Classification

This article presents an overview of the developments in stainless steels made since the 1990s. Some of the new applications that involve the use of stainless steel are also introduced. A brief introduction to the various classes of stainless steels, their precipitate phases and the status quo of their production around the globe is given first. The advances in a variety of subject areas that have been made recently will then be presented. These recent advances include (1) new findings on the various precipitate phases (the new J phase, new orientation relationships, new phase diagram for the Fe–Cr system, etc.); (2) new suggestions for the prevention/mitigation of the different problems and new methods for their detection/measurement and (3) new techniques for surface/bulk property enhancement (such as laser shot peening, grain boundary engineering and grain refinement). Recent developments in topics like phase prediction, stacking fault energy, superplasticity, metadynamic recrystallisation and the calculation of mechanical properties are introduced, too. In the end of this article, several new applications that involve the use of stainless steels are presented. Some of these are the use of austenitic stainless steels for signature authentication (magnetic recording), the utilisation of the cryogenic magnetic transition of the sigma phase for hot spot detection (the Sigmaplugs), the new Pt-enhanced radiopaque stainless steel (PERSS) coronary stents and stainless steel stents that may be used for magnetic drug targeting. Besides recent developments in conventional stainless steels, those in the high-nitrogen, low-Ni (or Ni-free) varieties are also introduced. These recent developments include new methods for attaining very high nitrogen contents, new guidelines for alloy design, the merits/demerits associated with high nitrogen contents, etc.

Recent developments in stainless steels

Chemical methods developed over the past two decades enable preparation of colloidal nanocrystals with uniform size and shape. These Brownian objects readily order into superlattices. Recently, the range of accessible inorganic cores and tunable surface chemistries dramatically increased, expanding the set of nanocrystal arrangements experimentally attainable. In this review, we discuss efforts to create next-generation materials via bottom-up organization of nanocrystals with preprogrammed functionality and self-assembly instructions. This process is often driven by both interparticle interactions and the influence of the assembly environment. The introduction provides the reader with a practical overview of nanocrystal synthesis, self-assembly, and superlattice characterization. We then summarize the theory of nanocrystal interactions and examine fundamental principles governing nanocrystal self-assembly from hard and soft particle perspectives borrowed from the comparatively established fields of micro...

Self-Assembly of Colloidal Nanocrystals: From Intricate Structures to Functional Materials

Poplar wood was treated with peracetic acid, KOH, and ball milling to produce 147 model lignocelluloses with a broad spectrum of lignin contents, acetyl contents, and crystallinity indices (CrIs), respectively. An empirical model was identified that describes the roles of these three properties in enzymatic hydrolysis. Lignin content and CrI have the greatest impact on biomass digestibility, whereas acetyl content has a minor impact. The digestibility of several lime-treated biomass samples agreed with the empirical model. Lime treatment removes all acetyl groups and a moderate amount of lignin and increases CrI slightly; lignin removal is the dominant benefit from lime treatment.

Fundamental factors affecting biomass enzymatic reactivity.

This best-selling comprehensive laboratory textbook includes experiments with background theoretical information, safety recommendations, and computer applications. Updated chapters are provided regarding the use of spreadsheets and other scientific software as well as regarding electronics and computer interfacing of experiments using Visual Basic and LabVIEW. Supplementary instructor information regarding necessary supplies, equipment, and procedures is provided in an integrated manner in the text.

Experiments in physical chemistry

Crystal structures of hydrated and dehydrated synthetic zeolites with faujasite aluminosilicate frameworks. I. The dehydrated sodium, potassium, and silver forms

: Beck and coworkers have found E phases in several ternary systems of transition elements with either silicon or germanium at the composition 1:1:1. The crystal structure of TiNiSi(E) has been determined and refined by least squares with (limited) three-dimensional single-crystal data to a final R value of 0.086 (excluding 002 due to apparent extinction, and all nonobserved reflexions). The lattice parameters for the primitive orthorhombic cell are: a sub 0 = 6.1484=0.0012, b sub 0 = 7.0173=0.0014, c sub 0 = 3.6698=0.0007 A. The E phase is isotypic with PbCl2(C23), space group Pnam. All near-neighbor distances are within 0.06 A of the following average values: Ti-Ti 3.18, Ti-Ni 2.83, Ti-Si 2.61, Ni-Ni 2.67, Ni-Si 2.33 A. The numbers of nearneighbors are compared with those in Co2Si, theta Ni2Si and U3Si2. (Author)

David P. Shoemaker

Papers

Experiments in physical chemistry

Crystal structures of hydrated and dehydrated synthetic zeolites with faujasite aluminosilicate frameworks. I. The dehydrated sodium, potassium, and silver forms

A ternary alloy with pbcl2-type structure: tinisi(e),

Critical evaluation of chemical and physical structural information.

The Crystal Structure of Ls-Threonine1