Inherent Difficulties (inherent + difficulty)

Distribution by Scientific Domains


Selected Abstracts


A perspective on MALDI alternatives,total solvent-free analysis and electron transfer dissociation of highly charged ions by laserspray ionization

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2010
Sarah Trimpin
Abstract Progress in research is hindered by analytical limitations, especially in biological areas in which sensitivity and dynamic range are critical to success. Inherent difficulties of characterization associated with complexity arising from heterogeneity of various materials including topologies (isomeric composition) and insolubility also limit progress. For this reason, we are developing methods for total solvent-free analysis by mass spectrometry consisting of solvent-free ionization followed by solvent-free gas-phase separation. We also recently constructed a novel matrix-assisted laser desorption ionization (MALDI) source that provides a simple, practical and sensitive way of producing highly charged ions by laserspray ionization (LSI) or singly charged ions commonly observed with MALDI by choice of matrix or matrix preparation. This is the first ionization source with such freedom,an extremely powerful analytical ,switch'. Multiply charged LSI ions allow molecules exceeding the mass-to-charge range of the instrument to be observed and permit for the first time electron transfer dissociation fragment ion analysis. Copyright © 2010 John Wiley & Sons, Ltd. [source]


The Challenge to the State in a Globalized World

DEVELOPMENT AND CHANGE, Issue 5 2002
Christopher Clapham
Individual instances of state failure and collapse must be placed within a broader appreciation of the evolution of statehood within the international system. The idea that the inhabited area of the globe must be divided between sovereign states is a recent development, and likely to prove a transient one. Largely the product of European colonialism, and turned into a global norm by decolonization, it is threatened both by the inherent difficulties of state maintenance, and by processes inherent in globalization. States are expensive organizations to maintain, not only in economic terms but also in the demands that they make on their citizens and their own employees. Poor and dispersed peoples, and those whose values derive from societies without states, have found these demands especially burdensome. The end of the Cold War and the collapse of the Soviet Union revealed the hollowness of existing models of sovereign states, and challenged the triple narratives on which the project of global statehood has depended: the narratives of security, representation, and wealth and welfare. While individual cases of state failure and collapse may owe much to specific circumstances and the behaviour of particular individuals, they must also be understood within the context of a world in which maintaining states has become increasingly difficult. [source]


Close-observation areas in acute psychiatric units: A literature review

INTERNATIONAL JOURNAL OF MENTAL HEALTH NURSING, Issue 3 2003
Louise O'Brien
ABSTRACT: Close-observation areas in Australian inpatient psychiatric units are locked areas usually within an open ward. Despite patient acuity, and the inherent difficulties in this area, little has been written that addresses either the processes or goals of containing patients, the role of nurses, or the skills involved. This paper examines the literature related to close-observation areas and argues that they are highly demanding of expert psychiatric nursing skills. Nurses need to advocate for humane, well-resourced areas, staffed with highly skilled nurses in order to fulfil the obligations of the national nursing and mental health service standards and to reduce the deleterious effects of hospitalization on patients. [source]


The burgeoning field of statistical phylogeography

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2004
L. L. Knowles
Abstract In the newly emerging field of statistical phylogeography, consideration of the stochastic nature of genetic processes and explicit reference to theoretical expectations under various models has dramatically transformed how historical processes are studied. Rather than being restricted to ad hoc explanations for observed patterns of genetic variation, assessments about the underlying evolutionary processes are now based on statistical tests of various hypotheses, as well as estimates of the parameters specified by the models. A wide range of demographical and biogeographical processes can be accommodated by these new analytical approaches, providing biologically more realistic models. Because of these advances, statistical phylogeography can provide unprecedented insights about a species' history, including decisive information about the factors that shape patterns of genetic variation, species distributions, and speciation. However, to improve our understanding of such processes, a critical examination and appreciation of the inherent difficulties of historical inference and challenges specific to testing phylogeographical hypotheses are essential. As the field of statistical phylogeography continues to take shape many difficulties have been resolved. Nonetheless, careful attention to the complexities of testing historical hypotheses and further theoretical developments are essential to improving the accuracy of our conclusions about a species' history. [source]


Laboratory Models Available to Study Alcohol-Induced Organ Damage and Immune Variations: Choosing the Appropriate Model

ALCOHOLISM, Issue 9 2010
Nympha B. D'Souza El-Guindy
The morbidity and mortality resulting from alcohol-related diseases globally impose a substantive cost to society. To minimize the financial burden on society and improve the quality of life for individuals suffering from the ill effects of alcohol abuse, substantial research in the alcohol field is focused on understanding the mechanisms by which alcohol-related diseases develop and progress. Since ethical concerns and inherent difficulties limit the amount of alcohol abuse research that can be performed in humans, most studies are performed in laboratory animals. This article summarizes the various laboratory models of alcohol abuse that are currently available and are used to study the mechanisms by which alcohol abuse induces organ damage and immune defects. The strengths and weaknesses of each of the models are discussed. Integrated into the review are the presentations that were made in the symposium "Methods of Ethanol Application in Alcohol Model,How Long is Long Enough" at the joint 2008 Research Society on Alcoholism (RSA) and International Society for Biomedical Research on Alcoholism (ISBRA) meeting, Washington, DC, emphasizing the importance not only of selecting the most appropriate laboratory alcohol model to address the specific goals of a project but also of ensuring that the findings can be extrapolated to alcohol-induced diseases in humans. [source]


What is the nature of the problem?

JOURNAL OF VIRAL HEPATITIS, Issue 2004
T. E. S. Delahooke
This review concentrates on the natural history of the infection. The virology and epidemiology of the disease are covered elsewhere. There are a number of inherent difficulties in studying the outcome of HCV infection: the onset is often not recognized, it can be asymptomatic, the progression is slow and patients may have had treatment. However some insights in recent years have been made. [source]


The early assessment conundrum: Lessons from the past, implications for the future

PSYCHOLOGY IN THE SCHOOLS, Issue 7 2004
Catherine M. Bordignon
The early childhood educational field has garnered attention with initiatives to foster skill acquisition in young children prior to kindergarten entry. These initiatives, in conjunction with the rigorous demands of curricular reform and a burgeoning accountability movement, invoke questions regarding the adequacy of the instruments used to assess young children and the inherent difficulties in conducting such assessments. Because the effectiveness of education relies critically on the sound diagnoses of children's readiness for learning and the measurement of their subsequent progression throughout the schooling process, critical issues in early assessment must be addressed. An examination of past practices was synthesized with recent research to focus awareness on the insufficient content domain, restrictive context, adverse timing and questionable psychometric properties, specifically the inappropriate norms and low predictive validity, of many instruments. Both the implications of and compensatory strategies for each issue are considered. © 2004 Wiley Periodicals, Inc. Psychol Schs 41: 737,749, 2004. [source]


Real Women or Objects of Discourse?

RELIGION COMPASS (ELECTRONIC), Issue 3 2009
The Search for Early Christian Women
Scholarly interest in gender and sexuality in early Christianity, which has typically been tied to an interest in women and women's roles, experiences, and influences, is a relatively new addition to the study of early church history. Women and women's issues entered the academy through the women's movement of the 1970s. Early on this scholarship was driven, in part, by a political or theological agenda that sought to empower women of the twentieth century by reconstructing the lives of their foremothers. Often the early studies of women in the church were optimistic that real, historical women could be found within our sources. Soon, however, scholars became more suspicious of the male-authored texts and turned, instead, to study the social effect of discourses about women. Many scholars, however, are not yet ready to give up investigations of ancient women's lives. Thus the field of early Christian studies is developing a variety of methodologies that offer sophisticated readings of ancient male-authored texts while still acknowledging the inherent difficulties involved in reconstructing women's lives in early Christian history. [source]


WILL THE DILEMMA OF EVIDENCE-BASED SURGERY EVER BE RESOLVED?

ANZ JOURNAL OF SURGERY, Issue 9 2006
Ned S. Abraham
Exponents of evidence-based medicine do not undermine the importance of clinical expertise and skills, but they emphasize that decision-making in medicine should be based on the best available evidence derived from the systematic analysis of observations made in an objective, unbiased and a reproducible fashion. The randomized controlled trial (RCT) is the most scientifically rigorous means of hypothesis testing in epidemiology. Discrepancies between established surgical and other interventions and best available evidence are common. These can be in the form of significant delay in adopting a new intervention despite strong supportive evidence, adopting an intervention before supportive evidence becomes available for reasons of novelty or pear pressure and the lack of supportive evidence for many established common practices. This is compounded further by the paucity of good quality evidence for most surgical procedures. This is arguably because of the inherent difficulties in conducting surgical RCT. The practical, ethical and financial ramifications are complex and the nature of surgical disease often compromise the chances of success or completion of RCT. Carrying out surgical RCT may have more implications on the clinician's authority, autonomy and income and their results are more likely to be influenced by his/her expertise and competence than medical RCT. Furthermore, the success of surgical RCT is often jeopardized by very low recruitment rates. The aim of this study is to discuss the dilemma of producing evidence in surgery. [source]


Delivering culturally appropriate residential rehabilitation for urban Indigenous Australians: a review of the challenges and opportunities

AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH, Issue 2010
Kate Taylor
Abstract Objective: To review the challenges facing Indigenous and mainstream services in delivering residential rehabilitation services to Indigenous Australians, and explore opportunities to enhance outcomes. Methods: A literature review was conducted using keyword searches of databases, on-line journals, articles, national papers, conference proceedings and reports from different organisations, with snowball follow-up of relevant citations. Each article was assessed for quality using recognised criteria. Results: Despite debate about the effectiveness of mainstream residential alcohol rehabilitation treatment, most Indigenous Australians with harmful alcohol consumption who seek help have a strong preference for residential treatment. While there is a significant gap in the cultural appropriateness of mainstream services for Indigenous clients, Indigenous-controlled residential organisations also face issues in service delivery. Limitations and inherent difficulties in rigorous evaluation processes further plague both areas of service provision. Conclusion: With inadequate evidence surrounding what constitutes ,best practice' for Indigenous clients in residential settings, more research is needed to investigate, evaluate and contribute to the further development of culturally appropriate models of best practice. In urban settings, a key area for innovation involves improving the capacity and quality of service delivery through effective inter-agency partnerships between Indigenous and mainstream service providers. [source]


Ultra-Stable Peptide Scaffolds for Protein Engineering,Synthesis and Folding of the Circular Cystine Knotted Cyclotide Cycloviolacin O2

CHEMBIOCHEM, Issue 1 2008
Teshome Leta Aboye
Abstract The cyclic cystine knot motif, as defined by the cyclotide peptide family, is an attractive scaffold for protein engineering. To date, however, the utilisation of this scaffold has been limited by the inability to synthesise members of the most diverse and biologically active subfamily, the bracelet cyclotides. This study describes the synthesis and first direct oxidative folding of a bracelet cyclotide,cycloviolacin O2,and thus provides an efficient method for exploring the most potent cyclic cystine knot peptides. The linear chain of cycloviolacin O2 was assembled by solid-phase Fmoc peptide synthesis and cyclised by thioester-mediated native chemical ligation, and the inherent difficulties of folding bracelet cyclotides were successfully overcome in a single-step reaction. The folding pathway was characterised and was found to include predominating fully oxidised intermediates that slowly converted to the native peptide structure. [source]


New school in liver development: Lessons from zebrafish,

HEPATOLOGY, Issue 5 2009
Jaime Chu
There is significant overlap in the genes and pathways that control liver development and those that regulate liver regeneration, hepatic progenitor cell expansion, response to injury, and cancer. Additionally, defects in liver development may underlie some congenital and perinatal liver diseases. Thus, studying hepatogenesis is important for understanding not only how the liver forms, but also how it functions. Elegant work in mice has uncovered a host of transcription factors and signaling molecules that govern the early steps of hepatic specification; however, the inherent difficulty of studying embryogenesis in utero has driven developmental biologists to seek new systems. The rapidly developing vertebrate zebrafish is a favorite model for embryology. The power of forward genetic screens combined with live real-time imaging of development in transparent zebrafish embryos has highlighted conserved processes essential for hepatogenesis and has uncovered some exciting new players. This review presents the advantages of zebrafish for studying liver development, underscoring how studies in zebrafish and mice complement each other. In addition to their value for studying development, zebrafish models of hepatic and biliary diseases are expanding, and using these small, inexpensive embryos for drug screening has become de rigueur. Zebrafish provide a shared platform for developmental biology and translational research, offering innovative methods for studying liver development and disease. The story of hepatogenesis has something for everyone. It involves transcriptional regulation, cell-cell interaction, signaling pathways, control of cell proliferation and apoptosis, plus morphogenic processes that sculpt vasculature, parenchymal cells, and mesenchyme to form the multifaceted liver. Decades of research on liver development in mice and other vertebrates offer valuable lessons in how the multipotent endoderm is programmed to form a functional liver. Of equal importance are insights that have illuminated the mechanisms by which hepatic progenitors are activated in a damaged liver, how the adult liver regenerates, and, possibly, the basis for engineering liver cells in vitro for cell transplantation to sustain patients with liver failure. Moreover, processes that are key to liver development are often co-opted during pathogenesis. Therefore, reviewing hepatogenesis is informative for both basic and translational researchers. In this review, we bring to light the many advantages offered by the tropical freshwater vertebrate zebrafish (Danio rerio) in studying hepatogenesis. By comparing zebrafish and mice, we highlight how work in each system complements the other and emphasize novel paradigms that have been uncovered using zebrafish. Finally, we highlight exciting efforts using zebrafish to model hepatobiliary diseases. (HEPATOLOGY 2009.) [source]


Limited effect of anthropogenic habitat fragmentation on molecular diversity in a rain forest skink, Gnypetoscincus queenslandiae

MOLECULAR ECOLOGY, Issue 2 2004
Joanna Sumner
Abstract To examine the effects of recent habitat fragmentation, we assayed genetic diversity in a rain forest endemic lizard, the prickly forest skink (Gnypetoscincus queenslandiae), from seven forest fragments and five sites in continuous forest on the Atherton tableland of northeastern Queensland, Australia. The rain forest in this region was fragmented by logging and clearing for dairy farms in the early 1900s and most forest fragments studied have been isolated for 50,80 years or nine to 12 skink generations. We genotyped 411 individuals at nine microsatellite DNA loci and found fewer alleles per locus in prickly forest skinks from small rain forest fragments and a lower ratio of allele number to allele size range in forest fragments than in continuous forest, indicative of a decrease in effective population size. In contrast, and as expected for populations with small neighbourhood sizes, neither heterozygosity nor variance in allele size differed between fragments and sites in continuous forests. Considering measures of among population differentiation, there was no increase in FST among fragments and a significant isolation by distance pattern was identified across all 12 sites. However, the relationship between genetic (FST) and geographical distance was significantly stronger for continuous forest sites than for fragments, consistent with disruption of gene flow among the latter. The observed changes in genetic diversity within and among populations are small, but in the direction predicted by the theory of genetic erosion in recently fragmented populations. The results also illustrate the inherent difficulty in detecting genetic consequences of recent habitat fragmentation, even in genetically variable species, and especially when effective population size and dispersal rates are low. [source]


Effect of AlGaAs cladding layer on GaInNAs/GaAs MQW p-i-n photodetector

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008
Y. F. Chen
Abstract The electronic properties of GaInNAs/GaAs multiple-quantum-well (MQW) p-i-n photodetector with AlGaAs cladding layer have been studied. By applying a higher band gap Al0.3Ga0.7As to the photodetector, a substantial reduction in dark current was observed owing to an inherent difficulty for holes to surmount the high potential barrier between MQW and the cladding layer heterojunction under a reverse bias. The dark current obtained was as low as 4.1 pA at -3.5 V for a device with Al0.3Ga0.7As cladding layer as compared to 22 ,A also at -3.5 V for a similar device without the Al0.3Ga0.7As cladding layer. The photo/dark current contrast ratios obtained were 4.2×104 and 11, respectively, for devices with and without an Al0.3Ga0.7As cladding layer at -3.5 V. In addition, peak responsivity of 1 mA/W was measured at around 1150 nm. Two orders of magnitude increase in the rejection ratio were realized between 1150 and 1250 nm at -2.0 V. The GaInNAs/GaAs MQW p-i-n photodetector was demonstrated with the AlGaAs cladding layer potentially providing a higher photo/dark current contrast ratio and higher responsivity rejection ratio. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]