bluuebunny/crossref_metadata_2025 huggingface dataset:
Titer Compounding of Neoprene Latex
Authors: Cook G. S. , Fitch J. C.
Published: February 2011

The practical importance of free alkali content on the processing and storage life of Neoprene latexes, both raw and compounded, is demonstrated. It is shown that titer measurements are more sensitive than pH measurements for establishing the alkali level of Neoprene latex, that increasing amounts of alkali increase markedly the life of both raw and compounded latexes, that increasing amounts of alkali decrease the original viscosity of compounds and reduce very much the viscosity increase which takes place during aging but, that, within the ranges checked, the alkali content has little effect on the physical properties of films. A procedure for measuring accurately and adjusting easily the free alkali content of raw latex to a desired level is suggested.
Chemigum SL—An Elastomeric Polyester-Urethane
Authors: Seeger N. V. , Mastin T. G. , Fauser E. E. , Farson F. S. , Finelli A. F. , Sinclair E. A.
Published: February 2011

A great deal of interest has been aroused in recent years in isocyanate chemistry by the announcement of new elastomers based on diisocyanate modification of polyesters. Early du Pont patent literature described diisocyanate modified alkyds, and Vulcaprene A, an elastomeric diisocyanate modified polyesteramide, has been offered to the rubber trade by Imperial Chemical Industries, Ltd., England. Several articles also have been published on Vulcollan by Bayer and associates on work done in the laboratories of Fabenfabriken Bayer Co., Leverkusen, Germany. More recently a new elastomeric polyester-urethane, Chemigum SL, was described by the Goodyear Tire and Rubber Co. These rubbers are first made in the form of processible and storable raw gums, having many of the characteristics of pale crepe natural rubber. They can then be mixed on the mill or in the Banbury with additional curatives, such as diisocyanates and other compounding agents, and cured in standard rubber molds. The cured physical properties of Chemigum SL are very similar to Vulcollan; both exhibit unusual toughness. Tensile strength is very high, as is resistance to cutting and chipping. Since the polyester-urethanes are saturated, cut-growth resistance is excellent. Even when cuts are initiated by sharp objects, there is no tendency to grow, even under stress. In this respect a vast superiority is shown over natural rubber or GR-S.
Surface Condition and Electrical Impedance in Rubber Friction
Authors: Schallamach A.
Published: February 2011

It is shown experimentally, by employing electrically conductive rubber, that, during the frictional gliding of rubber, a thin layer in contact with the track undergoes a deformation which considerably increases the electrical impedance of this layer. In the case of previously abraded rubber, the layer is permanent. If a d.c. potential is applied between sample and track during sliding, electrostatic attraction between sample and track is produced, and this increases the fractional force. The thickness of the layer, estimated from the magnitude of the electrostatic force, is a few thousandths of a centimeter.
Cracking of Stressed Rubber by Free Radicals
Authors: Crabtree J. , Biggs B. S.
Published: February 2011

The characteristic cracking of rubber by ozone has been well known for many years and has been the subject of numerous investigations. While this phenomenon has hitherto been considered unique with ozone, we find it not to be so, and that a cracking of rubber indistinguishable from that produced by ozone follows on exposure of stressed rubber to vapors of volatile peroxides irradiated by ultraviolet light. Moreover, the presence of oxygen is not necessary, the reaction occurring equally well in an atmosphere of nitrogen. Thus, the cracking apparently is due to the free radicals resulting from the photolysis of the peroxides. In the presence of nitrogen peroxide, the reaction is accelerated, as shown by an increase of the rate of rubber cracking and by a peroxide balance sheet, determined by chemical analysis. The photolyzed nitrogen peroxide evidently functions as a catalyst for the breakdown of the peroxide, since no change occurs in the dark. Cracking by such different radicals as tertiary-butoxy, phenyl, benzoyl, acetyl, and hydroxyl has been observed.
The Dissolution of Vulcanized Rubbers and Its Bearing on Problems of Rubber Analysis
Authors: Wake W. C.
Published: February 2011

Dissolution of a sample of vulcanized rubber is a necessary preliminary to several analytical procedures, e.g., the determination of iodine value or total fillers. If an infallible and convenient agent were available for this process, then doubtless other analytical procedures would be possible of development or improvement and examination of infrared transmission spectra of vulcanized samples would prove a feasible means of identification. Although decalin and nitrobenzene have been widely and satisfactorily used for natural rubber (polyisoprene), there have been several references in the literature to difficulties encountered with the most widely used synthetic rubber, GR-S. Devices to overcome these difficulties include comminution on a roller mill, swelling the sample in strong swelling agents before transferring to the solvent to be used for the dissolution, and grinding on a rubber mill with a plasticizer. All these must be regarded as being of the nature of palliatives, knowledge of the nature of the dissolution process being the real need before the best condition for carrying it out can be decided on. It is shown in this paper that the process is essentially oxidative in nature and, provided that the solvent and rubber are miscible at the temperature of the dissolution, temperature and efficient aeration are the most important rate-determining factors. The nature of the solvent is, of course, of importance with respect to the analytic procedure attempted as all solvents are not suitable for iodine value determination.
A New Gravitometer
Authors: Linhorst E. F.
Published: February 2011

Several months ago the Fort Wayne Plant of the United States Rubber Company began to use a new Jolly type of balance for determining the specific gravity of cured rubber. As shown in Figure 1, the apparatus employs two springs whose lower ends are joined to a metal rod that supports a moving scale V. A stationary scale A is placed parallel to the scale V. By using two springs instead of one, it is easier to bring the two scales close together.
Chain-Length Distribution Functions during Polymerization
Authors: Watson W. F.
Published: February 2011

Functions for the distribution of chain lengths of a polymer formed during polymerization have been evaluated in terms of the directly measurable rate and rate of initiation, or the single equivalent measurement of number-average chain length. No details of the reaction mechanism are required, except for the occurrence of termination by combination of polymer radicals. This is in contrast to the usual derivation of distribution functions from the postulated kinetic scheme. The three types of termination are considered, (1) combination absent, (2) combination predominant, and (3) a mixture of combination with other modes of termination. The application to copolymerization is outlined. Relationships between the various average molecular weights are considered.
A Precise Method for the Determination of the Width of a Dumbbell Test Specimen
Authors: Labbe B. G. , Leeper H. M.
Published: February 2011

The inaccuracy of stress-strain data in testing rubber samples is undoubtedly increased by variations of the width of the constricted area of the dumbbell test-specimen. Frequently a die for cutting these test-specimens is purchased and put into service without checking the width of the resulting dumbbell specimen. This situation often develops because of the uncertainty of the methods used for width determinations and the lack of suitable equipment for making the determinations, such as the cathetometer (microscope mounted on rod with cross wires and a scale). The cathetometer provides more accurate results than either the micrometer or the thickness gauge, but is open to the following objections: 1. The edge of the specimen is not always a well-defined line at the magnification necessary, and measurements made on a single strip varies with each observer. 2. Shadows must be completely eliminated because lighting of the sample is critical. 3. If the edges of the strip are not perpendicular to its lateral surfaces, recognition of the upper edge becomes difficult and uncertain. 4. If the sides of the specimen are slightly concave, as is sometimes the case, the cathetometric method yields false results that are high.
Dynamic Damping and Young's Modulus in the Range of Rubberlike Elasticity
Authors: Ecker R.
Published: February 2011

After a brief interpretation of current theoretical concepts of the high elasticity of macromolecular substances, as they have been developed by a number of authors from the laws of thermodynamics, the most important experimental methods of dynamic vibration are pointed out. A newly developed apparatus, which permits the study of the plastic-elastic behavior of high polymers in the rubber-elastic field by means of forced vibrations under tensile stress is described. With a plentiful supply of experimental material, various factors were studied, including the crystallization behavior of polymers, the reinforcing effect of various fillers, polymerization influences, modification of Neoprene-W by accelerators, the elastic behavior of Butyl and Silicone rubber, the influence of certain activators on the reinforcing properties of alumina gel, and the action of softeners in polyvinyl chloride.
Applied Force and Second Order Transitions of Rubber
Authors: Wall F. T. , Miller Donald G.
Published: February 2011

Second-order transitions, which appear to mark the change from brittleness to elasticity, are well known for rubber and numerous other polymers. The temperature at which such a transition occurs depends, among other things, on the kind of polymer, on the additives that are in it, and on how much it is cross-linked. It would also appear reasonable to expect that the second-order transition temperature would depend on the deformation of the sample, such as the elongation of a rubber strip. Accordingly, the research here reported was undertaken to investigate the effect of tension on rubber, in particular on rubbers with different degrees of cross-linking. The effect of such deformations might well provide further evidence regarding the nature of the phenomenon itself. Three different cures of natural rubber were used for comparing cross-linking effects. In addition, a sample of GR-S and a sample of rubber reinforced with carbon black were included for comparison. A decrease of Tm, the transition temperature, was found for these polymers when they were subjected to elongation. This problem has also been investigated previously for other polymers, a decrease in Tm likewise having been observed. The determination of the transition temperatures was carried out by observing the length of a strip as a function of the temperature; the break observed in the slope of the length vs. temperature curve was taken to mark the transition point. The results will be discussed on the basis that transitions are caused by the onset of segmental rotations with particular reference to the effect of cross-linking and forces of extension. The effects of swelling agents on Tm will also be discussed briefly.
The Microstructure of Diene Polymers. I. Polyisoprenes and Polybutadienes Prepared at High Temperatures
Authors: Richardson W. S.
Published: February 2011

In a previous paper a method has been described by which the microstructure of synthetic polyisoprenes can be deduced from intensity measurements in the infrared spectrum of these polymers. Similar analyses have been made in the case of polybutadienes by Hart and Meyer and by Hampton. It is the purpose of the present paper to present the results of structural determinations on polyisoprenes and polybutadienes prepared by bulk thermal polymerization in the temperature range 100 to 250° C.
Efficient Real-Time Video-in-Video Insertion into a Pre-Encoded Video Stream
Authors: Grois Dan , Kaminsky Evgeny , Hadar Ofer
Published: February 2011

This work relates to the developing and implementing of an efficient method and system for the fast real-time Video-in-Video (ViV) insertion, thereby enabling efficiently inserting a video sequence into a predefined location within a pre-encoded video stream. The proposed method and system are based on dividing the video insertion process into two steps. The first step (i.e., the Video-in-Video Constrained Format (ViVCF) encoder) includes the modification of the conventional H.264/AVC video encoder to support the visual content insertion Constrained Format (CF), including generation of isolated regions without using the Frequent Macroblock Ordering (FMO) slicing, and to support the fast real-time insertion of overlays. Although, the first step is computationally intensive, it should to be performed only once even if different overlays have to be modified (e.g., for different users). The second step for performing the ViV insertion (i.e., the ViVCF inserter) is relatively simple (operating mostly in a bit-domain), and is performed separately for each different overlay. The performance of the presented method and system is demonstrated and compared with the H.264/AVC reference software (JM 12); according to our experimental results, there is a significantly low bit-rate overhead, while there is substantially no degradation in the PSNR quality.
Oil Sands
Authors: Dusseault Maurice B. , Shafiei Ali
Published: February 2011

The article contains sections titled:1.Introduction2.Definitions3.Chemistry4.Viscous Oil Origins, Geological Setting and Resource Base Estimates4.1.Viscous Oil Origins4.2.Geographical Distribution and Resource Base Estimates4.3.Canadian Oil Sands Deposits4.3.1.The Athabasca Oil Sands4.3.2.The Cold Lake Oil Sands4.3.3.The Peace River Viscous Oil Sands4.3.4.The Wabiskaw Viscous Oil Sands4.3.5.The Heavy Oil Belt4.3.6.Venezuelan Viscous Oil Deposits4.4.Other Major Viscous Oil Deposits4.4.1.Russia4.4.2.Kazakhstan4.4.3.Kuwait4.4.4.China4.4.5.Iran5.In situ Production Technologies5.1.Historical Development5.2.Surface Mining5.3.New Oil Production Technologies5.3.1.Technical Screening Criteria for VO Production5.3.2.VO Production Cost Estimates5.3.3.Nonthermal Commercialized Methods5.3.3.1.Cold Production5.3.3.2.Cold Heavy Oil Production With Sand5.3.3.3.Pressure Pulse Stimulation Technology5.3.4.Commercialized Thermal Methods5.3.4.1.In Situ Combustion5.3.4.2.Conventional Steam Processes5.3.4.3.Vertical Well Cyclic Steam Stimulation5.3.4.4.Horizontal Well Cyclic Steam Stimulation5.3.4.5.Steam Assisted Gravity Drainage5.3.5.Emerging Methods5.3.5.1.Vapor‐Assisted Petroleum Production5.3.5.2.Toe‐to‐Heel‐Air Injection5.3.5.3.CAPRI5.3.5.4.Deep Miscible CO2Injection5.3.6.Hybrid Approaches and Sequencing of Technologies5.3.7.Geomechanics of Thermal VO Production5.3.8.Steam Generation5.3.9.Further Technical Issues6.Upgrading and Transportation6.1.Noncatalytic Processes in VO Upgrading6.1.1.Solvent Deasphaltening6.1.2.Thermal Conversion6.1.2.1.Gasification6.1.2.2.Delayed Coking6.1.2.3.Fluid Coking and Flexicoking6.1.2.4.Visbreaking6.2.Catalytic Processes in VO Upgrading6.2.1.Fluid Catalytic Cracking6.2.2.Hydroprocessing/Hydrogenation6.3.Hydrogen Sources6.4.Coke6.5.Sulfur Removal6.6.Future Developments in Upgrading6.7.Viscous Oil Transportation7.Environmental Issues7.1.Surface Mining Solid Wastes7.2.Surface Mining Liquid Wastes and Sludges7.3.In Situ Viscous Oil Recovery Processes7.4.Sulfur and Coke7.5.General Waste Management Options7.6.Zero Emissions Targets7.7.Greenhouse Gas Emissions7.8.Water Issues
Nondestructive Testing, 1. General
Authors: Ono Kanji , Dobmann Gerd
Published: February 2011

The article contains sections titled:1.Introduction2.Material Identification
Nondestructive Testing, 4. Thermography
Authors: Netzelmann Udo
Published: February 2011

The article contains sections titled:1.Introduction2.Developments in Detector Technology3.Excitation Techniques4.Signal Processing5.Selected Applications6.Summary and Outlook
Nondestructive Testing, 5. Magnetic and Electromagnetic Engineering
Authors: Ono Kanji , Dobmann Gerd
Published: February 2011

The article contains sections titled:1.Magnetic Particle Inspection2.Magnetic Leakage Field Inspection3.Micromagnetic Testing3.1.Historical Background3.2.Fundamentals3.3.Micromagnetic Measuring Techniques, Transducers, and Sensors3.4.The 3MA Approach3.5.Applications4.Eddy‐Current Inspection4.1.Fundamentals4.2.Detector Coils4.3.Giant Magneto Resistor Sensors4.3.1.Introduction4.3.2.Applications5.Microwave Inspection
Nondestructive Testing, 6. Nondestructive Testing in Civil Engineering
Authors: Wiggenhauser Herbert , Helmerich Rosemarie , Taffe Alexander , Krause Martin , Kind Thomas , Lai Wai‐Lok , Scheel Horst , Wilsch Gerd , Niederleithinger Ernst
Published: February 2011

The article contains sections titled:1.Introduction2.Testing Requirements in Civil Engineering3.Validation3.1.Validation Process3.2.Handheld Test Methods4.Ultrasonic Pulse Echo4.1.Ultrasonic Echo Testing (UPE) of Concrete Elements4.2.Performance4.3.Spatial Resolution4.4.Tendon Duct Investigations4.5.Practical Application5.Impact Echo6.Radar in Civil Engineering7.Corrosion Detection7.1.Ground‐Penetrating Radar7.2.Acoustic Emission (AE)8.Magnetic Flux Leakage (MFL)9.Laser‐Induced Breakdown Spectroscopy10.Foundation Testing10.1.Low‐Strain Pile Integrity Testing (PIT)10.2.Cross‐Hole Sonic Logging (CSL)10.3.Parallel Seismics10.4.High‐Strain Dynamic Testing11.Geophysical Methods
Nondestructive Testing, 7. Other Methods
Authors: Ono Kanji
Published: February 2011

The article contains sections titled:1.Visual and Optical Inspection2.Acoustic Emission2.1.Detection2.2.Material Behavior2.3.Source Location2.4.Acoustic Emission Monitoring3.Penetrant Methods4.Leak Testing4.1.Pressurized Gas Leaks4.2.Pressurized Liquid Leaks4.3.Vacuum System Leaks5.Uses5.1.Metallic Pressure Vessels and Piping5.2.Composite Pressure Vessels and Piping5.3.Weldments5.4.Other Uses
Paints and Coatings, 3. Paint Systems
Authors: Streitberger Hans‐Joachim , Urbano Edmund , Laible Richard , Meyer Bernd D. , Bagda Engin , Waite Frederick A. , Philips Michel
Published: February 2011

The article contains sections titled:

1.

Solventborne Paints

1.1.

Introduction

1.2.

Properties and Raw Materials

1.2.1.

Solvents

1.2.2.

Film Properties

1.3.

Application Technology and Environmental Protection

2.

Solvent‐Free and Low‐Solvent (High‐Solids) Paints

2.1.

Principles

2.2.

Production and Uses

2.2.1.

Alkyd Resins

2.2.2.

Polyester Resins

2.2.3.

Polyurethanes

2.2.4.

Acrylic Resins

2.2.5.

Epoxy Resins

2.2.6.

PVC Plastisols

3.

Waterborne Paints

3.1.

Properties

3.1.1.

Water‐Dispersible Binders (Secondary Dispersions)

3.1.2.

Polymer Dispersions (Emulsion Polymers, Primary Dispersions)

3.1.3.

Hybrid Systems

3.1.4.

Rheology Control of Waterborne Paints

3.1.5.

Internally and Externally Emulsified Binders

3.2.

Manufacturing and Application

3.3.

Uses and Environmental Aspects

4.

Coating Powders

4.1.

Introduction

4.2.

Manufacturing

4.3.

Properties

4.3.1.

Thermoplastic Binders

4.3.2.

Thermosetting Binders

4.3.3.

Colorants

4.3.4.

Other Constituents

4.4.

Testing

4.5.

Storage and Transportation

4.6.

Application

4.7.

Uses

4.7.1.

Thermosetting Coating Powders

4.7.2.

Thermoplastic Coating Powders

4.8.

Economic Aspects

4.9.

Environmental Aspects and Safety

5.

Emulsion Paints (Polymer Dispersions)

5.1.

Polymers

5.2.

Pigments

5.3.

Extenders

5.4.

Additives

5.5.

Production

5.6.

Properties

5.7.

Application

6.

Nonaqueous Dispersion Paints

7.

Radiation‐Curing Systems

7.1.

Introduction

7.2.

Resin Systems

7.3.

Radiation‐Curable Systems Based on Acrylates

7.3.1.

Prepolymers

7.3.2.

Monomers

7.4.

Additives

7.5.

Equipment

7.6.

Fields of Application

7.6.1.

Coatings

7.6.2.

Inks

7.6.3.

Adhesives

7.6.4.

Other Uses

8.

Electrodeposition Paints

8.2.

Properties

8.3.

Composition of Electrodeposition Baths

8.4.

Binders

8.5.

Uses

8.6.

Environmental Protection
Blood Coagulation
Authors: Neuenschwander Pierre F , Jesty Jolyon
Published: February 2011

The blood coagulation system acts in concert with the platelets to seal damaged blood vessels by the formation of a clot that consists of aggregated platelets interwoven with fibrin. Coagulation is initiated by the subendothelial membrane protein tissue factor and proceeds through a highly regulated proteolytic cascade to the production of
thrombin
and the
fibrin
clot. Although stoppage of blood leakage is the primary purpose of the coagulation system, many of the direct products of coagulation have additional functions that involve communicating with surrounding cells and crosstalk with other biochemical systems (i.e. inflammation and immunity). These secondary roles of the coagulation system products are vital for regeneration of tissue normalcy and overall homeostasis. Dysregulation of any of these coagulant system functions can lead to various clinical pathologies.

Key Concepts:

The initiator of coagulation, tissue factor, surrounds the vasculature in a protective haemostatic envelope.

The cascade design and feedback reactions in blood coagulation serve to rapidly amplify and dampen the response to create a burst of activity rather than a prolonged response.

Coagulation throw‐off products serve to signal the surrounding tissue to protect against pathogen invasion as well as initiate wound healing.
Plant Chimaeras and Mosaics
Authors: Bossinger Gerd , Spokevicius Antanas V
Published: February 2011

Plant chimaeras and mosaics are not only found in our gardens as variegated ornamentals. They also constitute valuable research tools with a range of applications in developmental and molecular biology. For example, much of our knowledge about the development of the shoot and root apical meristems is derived from studying patterns of variegation, and where patterns persist throughout the plant, deductions can be made as to the fate of individual meristematic cells and the number and arrangement of initial cells giving rise to a variety of plant organs or structures. At a molecular level, defined sectors can shed light on the cell autonomy of a certain trait, inform us about the propagation of molecular signals and indeed allow us to directly compare genetically distinct tissue sectors in an attempt to determine specific gene function.

Key Concepts:

Plant chimaeras comprise cells of distinct genomes, whereas in genetic mosaics, cells of different genotypes derived from the same zygote.

Cells with different genotypes or even from different species can communicate to form functional meristems and other tissues.

Continuous persistent sectors throughout a plant can be explained by a mosaic shoot apical meristem and can be used to create ‘developmental fate maps’.

The fate of most plant cells is determined late in development by their position rather than by their ancestry.

Sector boundary analysis is used to identify the number of cells set aside as progenitors of an organ.

Mosaic plants are used to analyse where a molecular signal originates and how it is propagated.

Sector analysis provides clues about the cell autonomy of a trait as well as specific gene function.
Methylation‐mediated Transcriptional Silencing in Tumorigenesis
Authors: Horan Martin P
Published: February 2011

Deoxyribonucleic acid
(DNA) methylation of promoter CpG (cytosine/guanine) islands is a process that inhibits the expression of genes through mechanisms that interfere with transcriptional initiation. Transcriptional silencing occurs when the 5′ flanking DNA region becomes heavily methylated, either allowing transcriptional repressor proteins to directly bind to the methylated DNA region or causing a conformational change in the DNA sequence. Thus, the downstream consequence of DNA methylation is to interfere with the binding and activational activity of specific transcription factors required for gene expression. The effect of DNA hypermethylation is therefore to inhibit or reduce the expression potential of a target gene. The role of methylation in cancer has been determined by association studies where the promoter regions of tumour suppressor genes have been found to be highly methylated. This is followed by gene silencing and an increase in tumour growth. Clinical interest in the treatment of tumours has gained increased impetus because recent evidence on the use of novel therapeutic agents suggests that DNA promoter methylation is potentially reversible. This may thus allow for the development of future therapeutic intervention.

Key Concepts:

Epigenetic methylation is a key mechanism that can inhibit or reduce gene expression in the absence of DNA sequence variations.

Aberrant DNA methylation may downregulate a gene as effectively as a pathological mutation.

CpG island methylation of tumour suppressor gene promoter regions is a mechanism responsible for silencing gene expression leading to tumour development.

Methylation of CpG islands can occur in regions of DNA that reside at great distances from a target gene but still lead to a reduction in gene expression.

Aberrant methylation of tumour suppressor genes is potentially reversible in tumours allowing for therapeutic intervention.
Evolution of VaultRNAs
Authors: Mosig Axel , Stadler Peter F
Published: February 2011

Vaultribonucleic acids(RNAs) are small, about 100 nt long, polymerase transcripts contained in the vault particles of eukaryotic cells. Although vaults are present in many but by no means all eukaryotes, an RNA component has been described in metazoa only. The RNAs exhibit conserved regions at the 3′ and 5′ ends containing also internal promoter elements. They form a panhandle‐like well‐conserved secondary structure. Most genomes contain only one or a small number of closely related vault RNA sequences. Only eutheria exhibit two clearly distinguished paralogues at syntenically conserved genomic locations. Their phylogenetic distribution is characterised by losses in major clades, whereas lophotrochozoa have vault particles and vault RNAs, and the entire system has been deleted in all ecdysozoa.

Key Concepts:

Vault RNA can be traced evolutionarily along with the vault particle and its key protein components, most notablyMVP.

Vault RNA exhibits a concserved pan‐handle secondary structure and expression patterns that are often mistaken as a microRNA.
Structure Determination by Single Particle Cryo‐electron Tomography
Authors: Hrabe Thomas , Förster Friedrich
Published: February 2011

Cryo‐electron Tomography (CET) is a method to image macromolecular assemblies three‐dimensionally in their native settings. Averaging of subtomograms, each containing a copy of a macromolecule of interest, offers substantially higher resolution insights into these macromolecules than CET alone. Here, we give an account of recent methodological advances in subtomogram averaging and approaches to capture structural heterogeneity of macromolecular complexes. Using these methods intermediate resolution insights (15–30 Å) into various membrane‐associated complexes and transient interactions between individual complexes in their physiological environment could be obtained. With further advances in hard‐ and software looming subtomogram analysis will play an increasingly important role in structural biology.

Key Concepts:

Cryo‐electron tomography images macromolecules in their physiological environment in 3D.

Averaging subtomograms depicting a macromolecular complex of interest yields higher resolution maps.

Subtomogram alignment and averaging is an optimisation problem.

Classification of subtomograms may separate different conformers in heterogeneous datasets and reveal corresponding densities.

Membrane‐associated complexes can be studied in their native membrane (
in situ
).

Transient interactions can be revealed from tomograms of whole cells and lysates.
Phosphoinositides – The Seven Species: Conversion and Cellular Roles
Authors: Lietha Daniel
Published: February 2011

Phosphoinositides are phospholipids that contain a phosphorylated inositol head group. The position and number of phosphate groups varies, which results in seven phosphoinositide species. A large family of enzymes have evolved to specifically modify phosphoinositides.Phosphoinositide kinasesandphosphatasesmodify the phosphorylation state of the inositol head group, whereas phospholipases hydrolyse phosphoinositides to release the soluble head group into the cytosol. The combined action of these enzymes produces the phosphoinositide signature of a cell, where certain membrane compartments are enriched or depleted of specific phosphoinositides. The cellular response of a certain phosphoinositide signature is mediated by phosphoinositide effectors. These effectors contain phosphoinositide recognition domains, which guide the effector to the appropriate location and in many cases also modulate their activity. Phosphoinositides play crucial roles in many cellular processes, including cell signalling, cytoskeletal rearrangements, vesicle transport and control of ion channels.

Key Concepts:

Phosphoinositides are phospholipids that contain a negatively charged phosphoinositol head group.

Phosphoinositides are modified by phosphoinositide kinases, phosphatases and phospholipases.

Specific phosphoinositides are enriched in different membrane compartments.

Specific phosphoinositide recognition modules are linked to effectors.

Tight regulation of generation and depletion of phosphoinositides allows spatio‐temporal control of complex cellular processes.

PI3KI and PTEN, which control PtdIns(3,4,5)P3levels, belong to the most frequently mutated genes in cancer.
Free Drug Monitoring
Authors: Dasgupta Amitava
Published: February 2011

Drugs are bound to various serum proteins in different degrees varying from 0% protein binding to 99% protein binding, but only unbound or free drug is pharmacologically active. Although free drug concentration can be estimated from total concentration knowing the extent of protein binding of a particular drug, for strongly bound drugs (more than 80% bound to serum protein), prediction of free level is not always possible. Conditions such as uremia, liver disease and hypoalbuminemia can lead to significant increases in free drug resulting in drug toxicity although the total drug concentration may be within the established therapeutic range. Drug–drug interactions are another major cause for disproportionate increases in free drug concentrations. Currently, free drug concentrations of anticonvulsants such as phenytoin, carbamazepine and valproic acid are widely measured in clinical laboratories. Newer drugs such as mycophenolic acid mofetil and certain protease inhibitors are also considered as good candidates for monitoring free drug concentration.

Key Concepts:

There are rationales for monitoring free drug concentration only for drugs that are strongly bound to serum proteins (80% or more).

Why free concentrations of phenytoin, valproic acid and carbamazepine are frequently monitored in certain patient population?

There is a need for monitoring free drug levels in uremia due to impaired protein binding of drugs as well as displacement of certain drugs from protein binding by ceratin uremic toxins.

There is a need for monitoring free drug concentrations in hepatic diseases due to impaired protein binding of certain drugs.

There is a need for monitoring free drug concentration in patients with hypoalbuminemia and critically ill patients due to elevated concentrations of free levels of drugs secondary to impaired protein binding.

There is a need for monitoring free drug concentrations in pregnancy due to change in protein binding and various other factors that affect clearance of certain drugs.

There is a need for monitoring free drug concentrations in AIDS patients due to impaired protein binding and probable drug–drug interactions.

Future candidates for monitoring free drugs include mycophenolic acid and protease inhibitors because these drugs are strongly bound to albumin and also have narrow therapeutic index.

Special case of monitoring free drug concentrations is digoxin, which is only 25% bound to serum proteins, but monitoring free digoxin in patients being treated with Digibind or taking certain herbal supplements is helpful to get clinically meaningful results.
Characterising Structural Variation by Means of Next‐Generation Sequencing
Authors: Ku Chee Seng , Naidoo Nasheen , Teo Shu Mei , Pawitan Yudi
Published: February 2011

A new era of copy number variants (CNVs) discovery began when two separate studies, published concurrently in 2004, identified several hundred deletions and duplications in the human genome. Over the past several years, most of the CNV data were generated by microarrays. These methods have several shortcomings, such as the inability to detect copy‐neutral variants (e.g. inversions and translocations), limited sensitivity to detect smaller CNVs and poor resolution in determining CNV breakpoints especially with lower resolution microarrays. A paradigm shift in the discovery of copy‐neutral variants was attributed to the development of a sequencing‐based method known as paired‐end mapping. This method was first demonstrated to be powerful in detecting structural variants using next‐generation sequencing technologies in 2007. Further studies have also leveraged an important feature of sequencing data, where several hundred million short sequence reads are produced by next‐generation sequencers, to detect CNVs based on the abundance or density of the sequence reads aligned to a reference genome. This approach is known as depth‐of‐coverage. These emerging sequencing‐based methods will continue playing an important role in the discovery of structural variants until

de novo

genome assembly becomes more feasible.

Key Concepts:

A new era of copy number variants (CNVs) discovery began when two separate studies, published concurrently in 2004, identified several hundred deletions and duplications in the human genome.

Both the sample size and the resolution of microarray are critical factors in determining the discovery of less common and smaller CNVs.

‘Human Genetic Variation’ was recognised as the ‘Breakthrough of The Year’ in 2007 by the journal
Science
.

Other types of chromosomal rearrangements, particularly inversions and balanced translocations, have received relatively less attention.

Inversions and translocations are also known as ‘copy‐neutral variants’ or ‘balanced chromosomal rearrangements’ and do not involve changes in copies number.

Collectively these copy number and copy‐neutral variants are broadly classified as ‘structural variants’.

The paradigm shift in the discovery of copy‐neutral variants was attributed to the development of the paired‐end mapping (PEM) method and concurrent advances in next‐generation sequencing technologies.

Further studies have also leveraged on an important feature of next‐generation sequencing data where several hundred million short sequence reads are produced to detect CNVs based on the density of the sequence reads aligning to the reference genome, and this approach is known as depth‐of‐coverage (DOC).

Although the PEM and DOC methods have overcome the major shortcomings of microarrays in detecting structural variants, these methods have their own weaknesses.

The emerging sequencing‐based methods (PEM and DOC) will continue to play a role in the discovery of structural variants until

de novo

genome assembly is more feasible
Basic Polyhedral Theory
Authors: Kaibel Volker
Published: February 2011

This chapter describes parts of the theory of convex polyhedra that are particularly important for optimization. The topics include polyhedral and finitely generated cones, the Weyl–Minkowski Theorem, faces of polyhedra, projections of polyhedra, integral polyhedra, total dual integrality and total unimodularity.
Clique Relaxations
Authors: McClosky Benjamin
Published: February 2011

In many applications, the structure of cliques can be restrictive and overly sensitive to data error. A recent line of research explores the various approaches to relaxing the clique concept. This article presents a brief survey of recent progress on this topic.
Product/Service Design Collaboration: Managing the Product Life Cycle
Authors: Johnson M. Eric
Published: February 2011

Product and service design collaboration allows supply chain partners to jointly develop and manage a product over its complete life cycle. From initial design conceptualization to end‐of‐life recycling, collaboration engages partners in a process of sharing information and decision rights. The goal of collaboration is to employ knowledge from across the supply chain to improve the product or service, reduce time to market, prevent supply chain mistakes, and ultimately increase profitability. Many web‐based tools have been developed to aid in this collaboration, creating an industry of software vendors. This article describes the role of design collaboration and illustrates its use through three case studies from different industries.
Cover Inequalities
Authors: Kaparis Konstantinos , Letchford Adam N.
Published: February 2011

Cover inequalities are a special kind of linear inequalities that are satisfied by the feasible solutions to knapsack problems. Although initially defined in the context of knapsack problems, cover inequalities and their variants can be used as cutting planes for a variety of integer programming and combinatorial optimization problems. We review the theory of these inequalities, discuss certain algorithmic aspects of them, and survey some of the applications.
Credit Risk Assessment
Authors: Novosyolov Arcady
Published: February 2011

The article describes a few credit instruments, indicates some risks associated with the instruments, and presents methods of credit risk assessment. First, we consider bond valuation, and assessment of interest rate risk via duration and convexity. Then, we move on to default risk, and use structural models for its assessment. Finally, we present an example of a wrong usage of a credit derivative tool that might lead to creating a derivative bubble.
CTMCs
with Costs and Rewards
Authors: Gautam Natarajan
Published: February 2011

We consider continuous‐time Markov chains (CTMCs) where there are costs and rewards associated with each state. For such a CTMC, the objective usually is to calculate either the long‐run average costs incurred per unit time or the total discounted cost incurred over an infinite horizon. We illustrate the calculations using several examples and conclude with applications to system performance analysis.
A Structural Clustering Algorithm for Large Networks
Authors: Xu Xiaowei
Published: February 2011

Networks such as the World Wide Web, social networks, and metabolic networks, which contain valuable information, draw increasing attention in scientific communities. Network clustering (or graph partitioning) is the discovery of underlying clusters of related vertices in networks. But, beyond organizing vertices into clusters of peers is the question of what role each vertex plays in the network. This article presents some new ways of uncovering underlying structures, including the roles that vertices play in the network. Identifying vertex roles is useful for applications such as viral marketing and epidemiology. For example, hubs are responsible for spreading ideas or disease. We applied our algorithm to analyze some real networks. The results demonstrate a superior performance over other methods such as modularity‐based algorithms.
Decomposition Algorithms for Two‐Stage Recourse Problems
Authors: Mayer János
Published: February 2011

In this article, decomposition methods for two‐stage linear recourse problems with a finite discrete distribution are discussed. First, we cover the L‐shaped decomposition method which represents a breakthrough concerning numerically efficient methods for solving two‐stage recourse problems. This algorithm was the basis for the development of several other decomposition methods. After giving an overview of these algorithms, we present regularized decomposition and stochastic decomposition in a more detailed fashion. Variance for recourse‐constrained problems and special cases including simple recourse with a random technology matrix are also considered. With reference to stochastic decomposition, the scope of which is not restricted to finite discrete distributions, algorithms for the continuous‐distribution case are discussed briefly with references to the literature.
Decomposition Methods for Integer Programming
Authors: Ralphs Ted K. , Galati Matthew V.
Published: February 2011

This article reviews both traditional and integrated decomposition methods for solving mixed‐integer linear programs. These methods attempt to exploit tractable substructures of the problem in order to obtain improved solution procedures. The goal is to derive improved methods of bounding the optimal solution value, which can then be used to drive a branch‐and‐bound algorithm. Such methods are the preferred solution approaches for a wide range of important models. To expose the desired substructure, a common approach is to relax a set of complicating constraints. This is the approach taken by the Dantzig–Wolfe decomposition, Lagrangian relaxation, and cutting‐plane methods. Substructure can also be exposed by relaxing the values of a set of variables, that is, considering restrictions of the original problem. This is the approach taken by Benders' decomposition. This article reviews decomposition methodologies based on relaxation of constraints and examines how they are used to solve mixed‐integer linear programs.
Definition and Examples of Continuous‐Time
M
arkov Chains
Authors: Uzun Evin
Published: February 2011

This article consists of definitions and examples of continuous‐time Markov chains (CTMCs). We first define a CTMC as a continuous‐time stochastic process that has a countable state space and the Markov property. Then, we restrict our attention to time‐homogenous CTMCs, for which we define the transition probability matrix. We further restrict our attention to regular CTMCs and provide an alternative definition of a CTMC. Next, we define the embedded discrete‐time Markov chain and the generator matrix of a CTMC and investigate the possible ways of characterizing a CTMC. We complete the definitions by defining the transition rate diagram of a CTMC. Finally, we conclude the article by providing examples of CTMCs.
Definition and Examples of
DTMCs
Authors: Gautam Natarajan
Published: February 2011

The objective of this article is to describe a special type of stochastic process called
discrete‐time Markov chain (DTMC)
. We first provide definitions for DTMCs using simple language as well as mathematics. Then, we describe a systematic technique to model a system as a DTMC. Finally, we provide examples to both illustrate the modeling technique and motivate the breadth of real‐world applications where DTMCs can be used.
Definition and Examples of Renewal Processes
Authors: Liu Liqiang
Published: February 2011

This article introduces an important class of stochastic processes called renewal processes, with definitions and examples.
Demand Responsive Transportation
Authors: Parragh Sophie N. , Doerner Karl F. , Hartl Richard F.
Published: February 2011

Demand responsive transportation systems are flexible public transportation services in which vehicle routes and schedules are generated on the basis of user requests. User requests consist of pickup and delivery location pairs. Problems of this kind are known asdial‐a‐ride problems. Since people are subject to transportation, the consideration of user inconvenience plays a central role. User inconvenience can either be limited by constraints or it can be considered in the objective function. It is usually expressed in terms of time windows, taking care of punctual service and maximum user ride time constraints, limiting the time a user should spend on a vehicle. In this article we review and discuss modeling aspects and solution methods for static and dynamic variants of the dial‐a‐ride problem.
Design for Network Resiliency
Authors: Tortorella Michael
Published: February 2011

“Network resiliency” has been used in common language for many years in a variety of contexts. The intent of the usage seems to always have included the notions that a resilient network is one that continues to deliver services in a satisfactory manner, despite possible disruptions in the network infrastructure and/or one that returns to normal operation quickly after a disturbance. In this article, we consider the former interpretation in detail. The notion of “satisfactory” obviously involves a matter of degree, so a consistent quantitative framework for network resiliency is proposed for the first interpretation. This article organizes and subsumes current streams of network resiliency thought by providing a generalization of the various notions that have been used in the past to describe network resiliency, and uses this generalization to create a quantitative framework for resiliency characterization. The key concepts are the notions of a network with associated delivery function and are of delivery importance. We discuss various design principles that promote greater network resiliency in the context of this framework. We introduce a network resiliency optimization scheme and briefly show how the network interdiction problem can be solved using the proposed network resiliency framework.
Disjunctive Programming
Authors: Balas Egon
Published: February 2011

Disjunctive programming, founded in the early 1970s, extends linear programming from optimization over polyhedra to optimization over disjunctive sets, which are equivalent to unions of polyhedra. It provides the tools for dealing with this particular class of nonconvex problems, of which integer programs are a special case. A central result is that optimizing over a union ofqpolyhedra inn‐space is equivalent to solving a linear program inO(q * n)‐space. The key idea that a higher‐dimensional reformulation of a difficult optimization problem may yield a more manageable model is by now commonplace, but its first systematic application goes back to disjunctive programming. Another basic result is that an important class of disjunctive sets, including the feasible sets of mixed 0–1 programs (but not of general mixed integer programs), can be convexified sequentially, that is, their convex hull can be generated by imposing the disjunctions one by one at each step, generating the convex hull of the current set. These and related results have led to the development of numerous classes of cutting planes for mixed integer programs, among them lift‐and‐project cuts, which played a crucial role in revolutionizing the state of the art of integer programming during the 1990s.
Domination Problems
Authors: Shen Siqian
Published: February 2011

In this article, we focus on dominating set problems in graphs. We review the literature that analyzes domination from different aspects, including bounds for the domination number, the algorithmic complexity, and valid inequality chains associated with each domination variant. In particular, we discuss the relationship between domination, independence, and irredundance, and reveal the well‐known domination chain and its properties. As many domination‐related problems can be solved in polynomial time for certain types of graphs (e.g., trees), we summarize start‐of‐the‐art results of polynomial algorithms regarding the domination‐related parameters of graphs. We also describe applications such as wireless ad hoc networks, social networks, and broadcast domination in which domination or its variants can be suitably implemented, as well as associated approximation algorithms, in order to emphasize the importance of the domination in graphs from a practical perspective.