Many Components (many + component)

Distribution by Scientific Domains


Selected Abstracts


Evaluation of creep damage accumulation models: Considerations of stepped testing and highly stressed volume

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 8 2007
W. A. GRELL
ABSTRACT Many components experience combined temperature and stress loading and are designed to withstand creep. In this study, experimental creep testing was performed under both static and stepped loading conditions with constant temperature for two specimen geometries (tensile and three-point bend). The objective of this study was to evaluate whether existing damage accumulation models accurately predict creep performance when considering step loading and stress gradients. Model predictions, based on static tensile creep data and using a highly stressed volume correction for the three-point bend specimens and the experimental average damage sum, agreed well with experimental data; differences were on average within 38% (static) and 2.2 h (stepped). Comparisons showed more accurate predictions using an exponential Larson,Miller parameter curve and the Pavlou damage accumulation model. Findings of the current study have applicability to component design, where complex geometries often contain stress gradients and it is desirable to predict creep performance from static tensile creep data. [source]


Ubiquitination in Abscisic Acid-Related Pathway

JOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 1 2007
Yi-Yue Zhang
Abstract Ubiquitination is emerging as a tight regulatory mechanism that is necessary for all aspects of development and survival of all eukaryotes. Recent genomic and genetic analysis in Arabidopsis suggests that ubiquitination may also play important roles in plant response to the phytohormone abscisic acid (ABA). Many components of the ubiquitination pathway, such as ubiquitin-conjugating enzyme E2, ubiquitin ligase E3 and components of the proteasome, have been identified or predicted to be essential in ABA biosynthesis, catabolism and signaling. In addition, the ubiquitination-related pathway, sumoylation, is also involved in ABA signaling. We summarize in this report recent developments to elucidate their roles in the ABA-related pathway. [source]


The metabolic syndrome: evolving evidence that thiazolidinediones provide rational therapy

DIABETES OBESITY & METABOLISM, Issue 4 2006
Kathleen L. Wyne
The metabolic syndrome, also known as the dysmetabolic syndrome, syndrome X or the insulin resistance syndrome, refers to the clustering of cardiovascular disease risk factors that are present in many individuals who are at increased risk for both cardiovascular events and type 2 diabetes. Prediabetic subjects typically exhibit an atherogenic pattern of cardiovascular risks that is associated with hyperinsulinaemia. Thus, identification of components of the metabolic syndrome is important if patients are to be treated early enough to prevent cardiovascular events and other complications related to diabetes. Therapies targeted to specific components of the metabolic syndrome such as improving glycaemic control, managing dyslipidaemia and reducing the prothrombotic state should help to minimize cardiovascular risk, particularly if initiated early. Traditional pharmacologic agents used to manage the individual components of the metabolic syndrome do not typically impact the other components. The thiazolidinediones, a new class of agents that improve insulin resistance, have the ability, in addition to their glucose-lowering effects, to exert several powerful anti-atherogenic properties, including anti-inflammatory effects in the vascular endothelium, redistribution of visceral fat and reduction of insulin resistance, hyperinsulinaemia and hyperproinsulinaemia. This makes the thiazolidinediones ideal candidates for the early treatment of many components associated with the metabolic syndrome. [source]


Evidence supporting an increased presence of reactive oxygen species in the diseased equine joint

EQUINE VETERINARY JOURNAL, Issue 5 2000
A. N. Dimock
Summary Reactive oxygen species (ROS) are capable of degrading many components of the joint in the presence of insufficient antioxidant defences, and as a result have been implicated in the pathogenesis of joint disease in horses. However, to our knowledge, evidence of ROS occurring in diseased joints of horses has not been reported. The objective of this experiment was to compare differences in synovial fluid protein carbonyl content (as a marker of oxidative modification of synovial fluid proteins by ROS) and the antioxidant status of synovial fluid between clinically normal and diseased equine joints. Synovial fluid was collected from the metacarpophalangeal, metatarsophalangeal, carpal and tarsal joints of 4 horses, age 2,5 years, as controls, and from diseased joints (metacarpophalangeal, metatarsophalangeal, carpal, tarsal and/or femoropatellar) of 61 horses, age 2,5 years. Synovial fluid protein carbonyl content was higher (P<0.01) in diseased joints as compared to controls. Antioxidant status of synovial fluid from diseased joints was higher, but not significantly, than that of controls (P = 0.0595). These findings require further study to determine their contribution to the overall disease process. [source]


Massive use of chemotherapy influences life traits of parasitic nematodes in domestic ruminants

FUNCTIONAL ECOLOGY, Issue 5 2001
V. Leignel
Summary 1,The size of nematodes is an operational indicator of fecundity. The variation in size due to chemotherapy was studied with a benzimidazole anthelmintic in susceptible and resistant nematodes. Teladorsagia circumcincta circumcincta (Stadelmann 1894), a nematode endoparasite of sheep and goats, was investigated as many components of its fitness are already known. 2,Susceptible worms submitted to increasing selective pressure by anthelmintics increased in size (by 6,10%); it was hypothesized that this was partly under the control of sheep, as treated lambs may mount and maintain a better response when infected (premunition). 3,The resistant worms, whatever the anthelmintic pressure, were always 3% larger than susceptible ones. 4,Thus, size may increase in susceptible worms and resistant worms for very different reasons. If resistance does not emerge, massive chemotherapy should lead to larger nematodes, and hence to more fertile worms. [source]


On the continuum approximation of large reaction mixtures

AICHE JOURNAL, Issue 7 2010
Teh C. Ho
Abstract In analyzing a reaction mixture of very many components, treating the mixture as a continuum can produce results of generality. In many practical situations (e.g., hydrodesulfurization), it is highly desirable to predict the overall behavior of the mixture at large times (high conversions) with minimum information on the mixture property. For irreversible first-order reactions in a plug-flow reactor, it was previously shown that the continuum approximation cannot be valid at arbitrarily large times. This work is an investigation of the validity of the approximation for mixtures with complex kinetics. It is found that the approximation can be conditionally or universally valid, depending on kinetics, reactor type, pore diffusion, and mixture properties. The validity conditions for a variety of situations, nontrivial as they may seem, take a power-law form. Backmixing and pore diffusion widen the range of validity. The underlying physics and some dichotomies/subtleties are discussed. The results are applied to catalytic hydroprocessing in petroleum refining. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]


Total projection to latent structures for process monitoring

AICHE JOURNAL, Issue 1 2010
Donghua Zhou
Abstract Partial least squares or projection to latent structures (PLS) has been used in multivariate statistical process monitoring similar to principal component analysis. Standard PLS often requires many components or latent variables (LVs), which contain variations orthogonal to Y and useless for predicting Y. Further, the X -residual of PLS usually has quite large variations, thus is not proper to monitor with the Q-statistic. To reduce false alarm and missing alarm rates of faults related to Y, a total projection to latent structures (T-PLS) algorithm is proposed in this article. The new structure divides the X -space into four parts instead of two parts in standard PLS. The properties of T-PLS are studied in detail, including its relationship to the orthogonal PLS. Further study shows the space decomposition on X -space induced by T-PLS. Fault detection policy is developed based on the T-PLS. Case studies on two simulation examples show the effectiveness of the T-PLS based fault detection methods. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]


A new method for the derivation of the closed nets in the phase diagram space of multisystems.

JOURNAL OF METAMORPHIC GEOLOGY, Issue 5 2004

Abstract A new convenient combinatorial method is developed here to derive the invariant points in multisystem closed nets , the absent phase substitution (APS) method. It substantially simplifies the derivation of the closed nets in multisystems with many components and phases. For the multisystems whose total phase number (NPS) , twice the number of the absent phases (m) in an invariant assemblage, the method can yield regular closed nets with or without globally absent phases; for other multisystems, the method can yield the regular closed nets with globally absent phases. As examples, the APS method was used to predict: (1) the regular closed nets of unary to quinary n + 4-phase multisystems, unary 6-phase multisystem and ternary 8-phase multisystem; (2) the basic properties of the regular closed nets of the quaternary and quinary multisystems with n + 4 and n + 5 phases. Two multisystems were chosen to demonstrate how to select a realistic closed net from the numerous possible closed nets of a complex multisystem, and how to derive a realistic partially closed-net, closed-net-diagram and the related realistic straight-line-net-diagram. Comparisons of our APS method for the derivation of complicated closed nets with other methods indicate that this method is much simpler and more efficient. [source]


Assessing patient category/dependence systems for determining the nurse/patient ratio in ICU and HDU: a review of approaches

JOURNAL OF NURSING MANAGEMENT, Issue 5 2004
PG Dip., Renee Adomat BA (Hons)
Background, A huge range of patient classification systems/tools are used in critical care units to inform workforce planning, however, they are not always applied appropriately. Many of these systems/tools were not originally developed for the purposes of workforce planning and so their use in determining the nurse:patient ratio required in critical care settings raises a number of issues for the organisation and management of these services. Aim, The aim of this paper is to review the three main assessment systems that are commonly used in critical care settings in the UK and evaluate their effectiveness in accurately determining nurse : patient ratios. If the application of these systems/tools is to enhance care, a thorough understanding of their origins and purpose is necessary. If this is lacking, then decisions relating to workload planning, particularly when calculating nurse : patient ratios, may be flawed. Conclusions, Patient dependency/classification systems and patient dependency scoring systems for severity of illness are robust measures for predicting morbidity and mortality. However, they are not accurate if used to calculate nurse : patient ratios because they are not designed to measure nursing input. Nursing intensity measures provide a useful framework for calculating the cost of providing a nursing service in critical care and can serve as a measure of nursing input, albeit a fairly basic one. However, many components of the nursing role are not ,accounted' for in these measures. Implications, The implications of these findings for the organization and management of critical care services are discussed. Careful consideration of these areas is vital if a cost efficient and cost-effective critical care service is to be delivered. [source]


The Biological Responses to Resveratrol and Other Polyphenols From Alcoholic Beverages

ALCOHOLISM, Issue 9 2009
Lindsay Brown
Although excessive consumption of ethanol in alcoholic beverages causes multi-organ damage, moderate consumption, particularly of red wine, is protective against all-cause mortality. These protective effects could be due to one or many components of the complex mixture of bioactive compounds present in red wine including flavonols, monomeric and polymeric flavan-3-ols, highly colored anthocyanins as well as phenolic acids and the stilbene polyphenol, resveratrol. The therapeutic potential of resveratrol, firstly in cancer chemoprevention and then later for cardioprotection, has stimulated many studies on the possible mechanisms of action. Further indications for resveratrol have been developed, including the prevention of age-related disorders such as neurodegenerative diseases, inflammation, diabetes, and cardiovascular disease. These improvements are remarkably similar yet there is an important dichotomy: low doses improve cell survival as in cardio- and neuro-protection yet high doses increase cell death as in cancer treatment. Fewer studies have examined the responses to other components of red wine, but the results have, in general, been similar to resveratrol. If the nonalcoholic constitutents of red wine are to become therapeutic agents, their ability to get to the sites of action needs to be understood. This mini-review summarizes recent studies on the possible mechanisms of action, potential therapeutic uses, and bioavailability of the nonalcoholic constituents of alcoholic beverages, in particular resveratrol and other polyphenols. [source]


A Study of CDK2 Inhibitors Using a Novel 3D-QSAR Method Exploiting Receptor Flexibility

MOLECULAR INFORMATICS, Issue 8 2009
Michael
Abstract A new 3D-QSAR method based on the novel molecular dynamics methodology, Active Site Pressurization (ASP), has been validated using two cyclin-dependent kinase 2 data sets containing 65 purines and 91 oxindoles. ASP allows the construction of cavity casts that represent the maximal energetically feasible 3D distortion of protein binding sites potentially achievable by induced fit upon binding of ligands. The ASP-QSAR method entails many components of traditional 3D-QSAR strategies but additionally correlates the biological activity of ligand sets with features of ASP-derived binding site cavity casts, thus taking target protein flexibility into account implicitly. Both of the data sets used to validate the ASP-QSAR method resulted in QSAR models that were of exceptional quality and predictivity. A non-cross-validated variance coefficient (R2) between 0.959 and 0.99 and a cross-validated variance coefficient (Q2) of between 0.927 and 0.929 were obtained for these ASP-QSAR models. [source]


The neuropathology of frontotemporal lobar degeneration with respect to the cytological and biochemical characteristics of tau protein

NEUROPATHOLOGY & APPLIED NEUROBIOLOGY, Issue 1 2004
S. Taniguchi
Pathological examinations, using a panel of tau and other antibodies, were performed on the brains from 55 consecutively acquired cases of frontotemporal lobar degeneration (FTLD). Clinically, these comprised 31 cases of frontotemporal dementia (FTD), 10 cases of motor neurone disease inclusion dementia (MNDID), seven cases of progressive aphasia (PA), four cases of semantic dementia (SD) and three cases of progressive apraxia (PAX). Tau pathology, in the form of neurofibrillary tangles (NFTs) and glial cell tangles, was present in six cases of FTD with parkinsonism linked to chromosome 17, five of these cases resulting from +16 splice-site mutation and one from +13 mutation in the tau gene. The insoluble tau proteins were comprised mostly of four-repeat (4-R) isoforms. Eight other cases of FTD, one of PA and all three cases of PAX showed tau-positive inclusions (Pick bodies) and swollen cells (Pick cells), characteristic of Pick's disease. In these cases, the insoluble tau proteins were present in most instances as three-repeat (3-R) tau isoforms, although two cases with a mixture of 3-R and 4-R isoforms were seen. One other case of FTD showed an unusual pathology characterized by massive extracellular deposition of tau protein, composed of 4-R tau isoforms, within white matter without neuronal or glial cell inclusions. However, 33 (60%) of 55 FTLD cases showed no tau pathology in the brain, except for the rare NFTs, composed of a mix of 3-R and 4-R isoforms, in some of the more elderly cases. Of these 33 cases, 13 had FTD, 10 had MNDID, six had PA and four had SD. The pathological changes present were those of a superficial cortical laminar microvacuolation with mild subpial and subcortical gliosis; the 10 MNDID cases had ubiquitin-positive inclusions in the cerebral cortex and hippocampus. These 33 nontau FTLD cases, along with five Alzheimer's disease (AD) and six Huntington's disease (HD) cases with severe pathology, showed a variable loss of soluble tau proteins, broadly comparable with the extent of neuronal loss from the cortex and loss of the intracortical perikaryal marker, NeuN, but unrelated to proteins within afferent projection fibres such as neurofilament and ,-synuclein. Levels of tau mRNA were decreased in parallel in the tau-negative FTLD cases and in the severe AD and HD cases. Hence, the loss of tau from these 33 nontau FTLD cases is just one aspect of a neurodegenerative process that destroys many components of the nerve cell machinery and does not represent a specific disordering of the cell's ability to form tau proteins or incorporate these into microtubules. [source]


How predictable are reptile responses to wildfire?

OIKOS, Issue 7 2008
David B. Lindenmayer
Natural disturbances are key processes in the vast majority of ecosystems and a range of ecological theories have been developed in an attempt to predict biotic responses to them. However, empirical support for these theories has been inconsistent and considerable additional work remains to be done to better understand the response of biodiversity to natural disturbance. We tested predictions from the intermediate disturbance hypothesis and the habitat accommodation model of succession for reptile responses to fire history and a single major fire event. We focused our work on a broad range of vegetation types spanning sedgeland to temperate rainforest located within a national park in south-eastern Australia. We found no significant relationships between reptile species richness and the number of fires over the past 35 years, the time since the last fire, or the severity of a major fire in 2003. Thus, we found no strong evidence to support the intermediate disturbance hypothesis. A correspondence analysis of reptile assemblages revealed a gradient in species responses to fire history. However, we found limited evidence for an ordered succession of reptiles. Nor could the responses of individual species be readily predicted from life history attributes. Thus, our findings were generally not consistent with predictions from the habitat accommodation model of succession. A possible explanation for the absence of a predictable sequence of recovery following disturbance might be the rapidity of post-fire recovery of many components of native vegetation cover that were found to be important for reptiles (e.g. the extent of grass cover). This would have limited the time for early successional conditions to prevail and limited opportunities for species associated with such conditions. We found that most reptile species responses were much more strongly linked to vegetation type than fire variables, emphasizing a need to understand relationships with vegetation before being able to understand possible fire effects (if and where they exist). We found the disturbance concepts we examined were limited in their ability to accurately predict reptile responses to past fire history or the impacts of a single major fire in 2003. Practical management might be best guided not by disturbance theory, but by carefully setting objectives to meet conservation goals for particular individual species of reptiles. [source]


Reproductive ecology and the endometrium: Physiology, variation, and new directions

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue S49 2009
Kathryn B.H. Clancy
Abstract Endometrial function is often overlooked in the study of fertility in reproductive ecology, but it is crucial to implantation and the support of a successful pregnancy. Human female reproductive physiology can handle substantial energy demands that include the production of fecund cycles, ovulation, fertilization, placentation, a 9-month gestation, and often several years of lactation. The particular morphology of the human endometrium as well as our relative copiousness of menstruation and large neonatal size suggests that endometrial function has more resources allocated to it than many other primates. The human endometrium has a particularly invasive kind of hemochorial placentation and trophoblast that maximizes surface area and maternal,fetal contact, yet these processes are actually less efficient than the placentation of some of our primate relatives. The human endometrium and its associated processes appear to prioritize maximizing the transmission of oxygen and glucose to the fetus over efficiency and protection of maternal resources. Ovarian function controls many aspects of endometrial function and thus variation in the endometrium is often a reflection of ecological factors that impact the ovaries. However, preliminary evidence and literature from populations of different reproductive states, ages and pathologies also suggests that ecological stress plays a role in endometrial variation, different from or even independent of ovarian function. Immune stress and psychosocial stress appear to play some role in the endometrium's ability to carry a fetus through the mechanism of inflammation. Thus, within reproductive ecology we should move towards a model of women's fecundity and fertility that includes many components of ecological stress and their effects not only on the ovaries, but on processes related to endometrial function. Greater attention on the endometrium may aid in unraveling several issues in hominoid and specifically human evolutionary biology: a low implantation rate, high rates of early pregnancy loss, prenatal investment in singletons but postnatal support of several dependent offspring at once, and higher rate of reproductive and pregnancy-related pathology compared to other primates, ranging from endometriosis to preeclampsia. The study of the endometrium may also complicate some of these issues, as it raises the question of why humans have a maximally invasive placentation method and yet slow fetal growth rates. In this review, I will describe endometrial physiology, methods of measurement, variation, and some of the ecological variables that likely produce variation and pregnancy losses to demonstrate the necessity of further study. I propose several basic avenues of study that leave room for testable hypotheses in the field of reproductive ecology. And finally, I describe the potential of this work not just in reproductive ecology, but in the resolution of broader women's health issues. Yrbk Phys Anthropol 52:137,154, 2009. © 2009 Wiley-Liss, Inc. [source]


Determining Thermal Test Requirements for Automotive Components

QUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 2 2004
Dustin S. Aldridge
Abstract Component thermal response is dependent upon numerous factors including the atmospheric temperature, heat sinks and sources, vehicle use time, etc. The number of significant thermal cycles and time at temperature for many components will be related to the number of times the engine is started. This paper provides a methodology to determine the number of significant thermal cycles and time at temperature a product will experience in 10 years which will depend upon engine starts. These calculations provide the basis for an accelerated test requirement to qualify the product based upon customer usage measurements. Because of the trace ability and linkage, the methodology is more marketable to internal and external customers, and less likely to be questioned or arbitrarily overruled. It also enables relative severity assessments for historical customer requirements compared with field needs. Copyright © 2004 John Wiley & Sons, Ltd. [source]


The potential role of purine-rich element binding protein (PUR) , as a novel treatment target for hormone-refractory prostate cancer,

THE PROSTATE, Issue 10 2008
Takahiro Inoue
Abstract BACKGROUND Hormonal therapy for advanced prostate cancer is typically effective at first, but almost all men suffer refractory disease which often is life threatening. The nuclear matrix comprises not only of the structural elements of the nucleus, but is associated with many components of the molecular machinery. Our aim is to find novel targets for the treatment of hormone-refractory prostate cancer (HRPC) by focusing on the composition of the nuclear matrix proteins (NMPs). METHODS LN96 cells were established at our Institution after long-term culturing of LNCaP cells under androgen deprived conditions. The composition of NMPs of LNCaP cells and LN96 cells were analyzed by two-dimensional (2D) electrophoresis and spots differentially expressed were investigated by mass spectrometry for identification. Among the spots identified, we analyzed the potential functional role of the identified proteins in prostate cancer cells by establishing stable overexpressed cells. RESULTS We found that purine-rich element binding protein (PUR), was significantly repressed not only in NMPs but also in total protein and mRNA levels of LN96 cells in comparison to LNCaP cells under the same steroid deprived conditions. Moreover, PUR, was decreased in its expression both at the protein and mRNA levels in the androgen-independent prostate cancer cell lines, PC3 and DU145 in comparison to LNCaP cells. Stably overexpressing PUR, in PC3 and DU145 cells negatively regulates cell proliferation, resulting in decreases in PCNA expression. CONCLUSION Further dissection of the role of PUR, in cell growth regulation may reveal a novel target for HRPC. Prostate 68:1048,1056, 2008. © 2008 Wiley-Liss, Inc. [source]


Uveal melanoma and macular degeneration: molecular biology and potential therapeutic applications

ACTA OPHTHALMOLOGICA, Issue 8 2008
Mario-Alexander Economou
Abstract. Uveal melanoma is the most common primary intraocular malignant tumor in adults with 30% to 50% of patients that ultimately succumb to metastatic disease, mainly to the liver. (Shields et al. 1991) Although new diagnostic and therapeutic tools have been developed during the most recent years, only the eye conservation rate has been achieved, while the survival rate remains poor. The reason for this liver-homing is largely unknown, but it is conceivable that hepatic environmental factors may be implicated in the growth, dissemination, and progression of this malignancy. The insulin-like growth factor (IGF-1) that binds to the IGF-1 receptor (IGF-1R) is mainly produced in the liver. It has been shown to be crucial for tumor transformation, maintenance of malignant phenotype, promotion of cell growth, and prevention of apoptosis. (Baserga 1995) The hepatocyte growth factor/scatter factor (HGF/SF) is another growth factor produced in the liver and exerts its biological effects through binding to the plasma membrane receptor c-Met. The activation of this receptor by HGF/SF ligand can induce proliferation, motility, adhesion, and invasion of tumor cells. (Cruz et al. 2003) Metastasis is a process involving many components, including tumor cell adhesion, migration, extracellular matrix (ECM) proteolysis, and invasion. The tumor cells undergo intravasation, disperse via the vascular and the lymphatic systems, and finally extravasate to invade the secondary sites. In all these steps, proteolytic enzyme systems are involved, including the matrix metalloproteinase (MMP) system and the plasminogen activation system. The migration of a malignant cell through the ECM and the basement membrane requires proteolytic activities. (Stetler-Stevenson et al. 1993). Efforts to target the IGF-I system has been made with different types of cancer but not with uveal melanoma. [source]


Traditional therapies: glucocorticoids, azathioprine, methotrexate, hydroxyurea

CLINICAL & EXPERIMENTAL DERMATOLOGY, Issue 7 2002
G. Belgi
Summary The ,old favourites' used for treatment of inflammatory diseases, and hence, the original immunomodulators, include the glucocorticoids, azathioprine, methotrexate and hydroxyurea. Glucocorticoids are still one of the most effective anti-inflammatory agents because they work on several different intracellular processes and hence, block many components that contribute to inflammatory and immune responses. They bind to intracellular glucocorticoid receptors which transport them into the nucleus. Here the receptor/steroid complex may bind to many genes that interact with transcription factors including NF,B and AP-1, to inhibit their activation, thereby preventing activation of many genes encoding immune effector and pro-inflammatory cytokines. Also, protein kinases involved in intracellular signalling, are directly activated resulting in phosphorylation of various targets of which Annexin (AXA)-1 is critical in inhibiting biosynthesis of both purines and DNA. This results in reduced proliferation of B and T lymphocytes, reduced immune effector mechanisms and reduced recruitment of mononuclear cells including monocytes into sites of immune inflammation. Methotrexate also blocks DNA synthesis and hence cellular proliferation but also induces release of adenosine. This inhibits chemotaxis of polymorph neutrophils and release of critical cytokines such as TNF-, and Interleukins 6 and 8. Hydroxyurea also inhibits DNA synthesis with inhibitory effects on proliferation of lymphocytes and possibly kerationcytes. Even though many new agents with much greater selectivity are coming through into clinical use, this group of old agents still have an absolutely central position in the therapeutic armamentarium. Their value lies in the fact that they are not ,clean' drugs with narrow effects but they inhibit a wide range of mechanisms involved in immune and inflammatory processes. [source]