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Medical Sciences	50%

Selected Abstracts

Dialyzer reactions in a patient switching from peritoneal dialysis to hemodialysis

HEMODIALYSIS INTERNATIONAL, Issue 2 2005
Robert C. Yang
Many terms have been used to describe the collection of signs and symptoms triggered by the initial use of dialyzers. These reactions can be divided into Type A (hypersensitivity reactions, with the incidence of 4/100,000) and Type B (nonspecific reactions, incidence 3,5/100). Many different mechanisms have been postulated, including complement activation, pulmonary leukostasis, hypersensitivity to ethylene oxide, interaction between the AN69 membrane and angiotensin-converting enzyme inhibitors, and dialysate contamination. An unusual case of dialyzer reactions is presented here, involving a patient who had to discontinue peritoneal dialysis when she was admitted with fungal peritonitis. Upon initiation of hemodialysis, she experienced dyspnea and burning sensation and demonstrated significant leukopenia, thrombocytopenia, and oxygen desaturation. These reactions persisted despite double-rinsing of the dialyzers and the use of several different dialyzers with synthetic membranes (polysulfone and AN69), and a variety of sterilization methods (electron beam and gamma radiation). In the end, a simple measure was found to be effective in preventing further dialyzer reactions in this fascinating case. [source]

The Effect of Insomnia Definitions, Terminology, and Classifications on Clinical Practice

JOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue S7 2005
Andrew D. Krystal MD
There is a need for newer, more clinically useful classifications for insomnia. Identification of specific subtypes of insomnia helps anchor research, allows for prediction of prognosis/course of the condition, and may allow for individualization of treatment. Existing classifications differ, and many terms remain inadequately defined, which leads to diagnostic confusion. Historically, insomnia has been classified according to symptom type, symptom duration, and underlying cause, but these classifications have not been based on evidence of their utility, and newer research suggests the need for change. Symptoms may include difficulty falling asleep, trouble staying asleep, and not feeling restored by sleep, although it has not been clear that it is possible to identify distinct subtypes of patients by symptom or that distinguishing symptom type affects the course of clinical treatment. Classification of insomnia by duration most commonly involves three categories: transient (no more than a few days), short-term (up to 3 weeks), and long-term (more than 3 weeks). This categorization is of uncertain utility and has been primarily based on nonempiric concerns about treatment with sedative-hypnotic medications for periods longer than several weeks. The subtyping of insomnia in terms of whether there is an identifiable underlying cause such as a psychiatric or medical illness was based on an unproven assumption that in most instances other disorders caused insomnia. Recent studies suggest the need to revisit these classification strategies. Evidence that symptom types typically overlap and change over time complicates the categorization of subjects by whether they have difficulty falling asleep or staying asleep or have nonrestorative sleep. New studies of the treatment of chronic insomnia change the perspective on duration of treatment and, as a result, classification of duration of disease. Two studies of nightly pharmacotherapy for insomnia including more than 800 insomnia patients have not identified any increase in the risks after 3 to 4 weeks of treatment. In addition, nonpharmacological treatments demonstrate long-lasting efficacy in patients with chronic insomnia, and the development of abbreviated cognitive-behavioral therapies, which are particularly well suited to primary care practice, have improved their applicability. Newer studies of the relationships between insomnia and associated medical and psychiatric conditions undermine the notion that insomnia is always a symptom and caused by an underlying condition. They suggest that, although it is important to identify and treat these conditions, this may not be sufficient to alleviate the insomnia, which may adversely affect the course of the associated disorder. As a result, treatment targeted specifically to the insomnia should be considered. All of these developments point to an increasing ability to tailor therapy to the particular needs of patients and to optimize the clinical management of insomnia. [source]

Bodensystematik und Bodenklassifikation Teil I: Grundbegriffe

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 1 2005
Christoph Albrecht
Abstract Bodenordnungssysteme lassen sich meist nach zwei Prinzipien entwickeln: Entweder werden nur rein bodenkundliche Informationen als kategorisierendes Merkmal verwendet (pedogenetische Faktoren/Prozesse), oder die Kategorienbildung erfolgt problemorientiert anhand ausgewählter Parameter. Die meisten der weltweit verwendeten Bodenordnungssysteme lassen sich nach ihrer Grundausrichtung einem der beiden Typen zuordnen. Diese Betrachtungsweise ist nicht neu und wird in der Literatur mit unterschiedlichen Begriffen und Begriffsinhalten dargestellt. In der vorliegenden Arbeit werden die verschiedenen Definitionen von Systematik, Klassifikation, Taxonomie und Identifizierung zusammengefasst und geordnet. Dabei fällt auf, dass Begriffe mit sehr unterschiedlichen Inhalten oft synonym verwendet werden. Grundgedanke unserer Überlegungen ist die Trennung von Systematik, Klassifikation und Identifizierung. Systematik ist die grundsätzliche wissenschaftlich-deduktive Gliederung von Objekten in systematische Einheiten. Dabei soll das gesamte Wissen eines Fachgebietes in eine überschaubare Form gebracht werden, im Mittelpunkt stehen sowohl die umfassende Beschreibung einzelner Objekte als auch die Beziehungen zwischen den Objekten. Im Gegensatz dazu ist eine Klassifikation die zielorientiert-induktive Gliederung von Objekten. Die entstehenden Klassen werden nur anhand ausgewählter Parameter abgegrenzt, womit ein schneller Überblick bei speziellen Fragestellungen ermöglicht wird. Die Identifizierung ist die Einordnung von neuen Objekten in eine bestehende Systematik oder Klassifikation. Eine zweifelsfreie Identifizierung erfordert die Messbarkeit der kategorisierenden Merkmale. Bei einer genetisch angelegten Bodensystematik sind die Merkmale die Boden bildenden Prozesse und Faktoren. Da sie beim gegenwärtigen Kenntnisstand oft nicht messbar sind, bleiben Versuche, einen Boden in eine Systematik einzuordnen, häufig hypothetisch und dadurch subjektiv. Die Ergebnisse einer Bodensystematisierung sind daher oft anfechtbar, weil sie nicht durch Messwerte verifiziert werden können. Im Gegensatz dazu erlauben Bodenklassifikationen objektive Profilansprachen. Da jedoch die Festlegung der Grenzwerte eher pragmatisch nach Zweckmäßigkeit geschieht und nicht wissenschaftlich anhand von Prozessintensitäten, ist die Verwendung als grundlegendes Ordnungssystem eines Wissenschaftsgebietes nicht möglich. Die Bodenkunde benötigt beide Arten von Ordnungssystemen, um wissenschaftliche und praktische Ansprüche gleichermaßen erfüllen zu können, jedoch erfordern die Vollendung und Verifizierung der Systematik umfangreiche Forschungsarbeiten. Kurzfristig ist dieses Problem nur durch die Entwicklung einer kennwertbasierten Klassifikation lösbar, mit der die Kategorien der bestehenden Systematik so gut wie möglich nachgebildet werden. Langfristig ist die exakte Erforschung und Modellierung der Boden bildenden Prozesse aber unumgänglich. Soil systematics and classification systems Part I: Fundamentals Soil-ordering systems are primarily based and developed on one of two underlying principles: They are either categorized according to soil-forming processes, or the formation of categories develops by chosen parameters. This perspective has already been established in the literature, though it is often confusing as many terms are defined and applied differently. In this contribution, the various definitions of systematics, classification, taxonomy, and identification will be clearly differentiated and summarized. The core of our work is to clearly define and contrast three terms: systematics, classification, and identification. Systematics is the fundamental scientific and deductive ordering of objects into systematic units. The purpose of this approach is to organize the entire spectrum of knowledge within a discipline into a transparent and manageable form. Classification, in direct contrast to systematics, is goal-oriented and an inductive ordering of objects. Thus, the ordering scheme consists of classes which are clearly parameterized. Identification is the ordering of new objects into an already existing systematics or classification system. Close attention is paid to both the differences and the similarities between a systematics and a classification system, especially pertaining to their practical applications. The identification requires that the category-forming characteristics can be measured (e.g., for soil systematics, these are the soil-forming processes and factors). Currently, it is unfortunately not feasible to objectively quantify most soil-forming processes. Thus, most attempts at categorizing soils by systematics are hypothetical and highly subjective in nature. The resulting identification derived from the soil systematics approach is open to questions and contestable, since a graded measuring system does not yet exist to verify these determinations. In contrast, a soil-classification system does allow an objective soil-profile identification, although such systems are conceived pragmatically and designed for a practical purpose (e.g., not scientifically based on process intensities). Unfortunately, such a classification system cannot be applied as a universal scientific categorization system due to this method of conception. Both categorization approaches are required in soil science in order to satisfy both the practical and the scientific aspects of the field. However, substantial research must be done to complete and verify systematics. The only viable short-term solution is through the development of a graded classification system where the categories of the system are directly derived from the current systematics approach. In the long run both the exact investigation and the detailed modeling of the soil-forming processes are inevitable. [source]

X-ray atomic orbital analysis.

ACTA CRYSTALLOGRAPHICA SECTION A, Issue 4 2008

The scattering unit of X-ray crystal structure analysis is changed from atoms to the subshell electrons by X-ray atomic orbital analysis (XAO). All the atoms in the unit cell are divided into groups of subshell electrons in the XAO analysis. Each subshell is treated as an independent pseudo-atom, which enables the atomic orbitals (AO's) and the electron population of each AO expressed as a linear combination of s/p/d/f orbitals in each subshell to be determined. When the environmental condition of the sample is varied, the electron transfer among the AO's in the crystal can be traced with XAO. It is applicable mainly to analyses of the electron-density distribution in ionic solids including those with a nonstoichiometric structure. The expansion coefficients of each AO are calculated with the perturbation theory putting a point charge on each atom in the unit cell. This automatically makes the perturbation potential have the point-group symmetry of the atom in the crystal field. Then the coefficients of each AO are refined to fit to the observed structure factors keeping the orthonormal relationships among the AO's. Complex basis functions with , or , spin as well as real ones are employed for heavy atoms and the relationships among the coefficients for the AO's of an electron in the crystal fields of the 32 point-group symmetries are derived for p, d and f orbitals. The AO's thus derived can be applicable to an anti-symmetrized multi-electron system, although X-ray diffraction cannot specify the atomic terms occupied when the crystal symmetry permits the atom to have many terms. [source]