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PubMed1998

The role of library and information services in the modular curriculum.

Radical changes in nurse education, accompanied by advances in library and information services (LIS), set against a background of ever-expanding nursing literature and information, have favoured the development of good practices in curriculum development and student-centred learning. This paper discusses the experience at Keele University of enhanced collaborative effort between curriculum planners and LIS staff, and aims to show how LIS can facilitate student learning and contribute to curriculum planning and delivery, quality resource provision, evaluation processes and life-long learning.

Abstracting and Indexing↗
PubMedDate not supplied

Ton-dependent colicins and microcins: modular design and evolution.

Ton-dependent colicins and microcins are actively taken up into sensitive cells at the expense of energy which is provided by the proton motive force of the cytoplasmic membrane. The Ton system consisting of the proteins TonB, ExbB and ExbD is required for colicin and microcin import. Colicins as well as the outer membrane transport proteins contain proximal to the N-terminus a short sequence, called TonB box, which interacts with TonB and in which point mutants impair uptake. No TonB box is found in microcins. Colicins are composed of functional modules which during evolution have been interchanged resulting in new colicins. The modules define sites of interaction with the outer membrane transport genes, TonB, the immunity proteins, and the activity regions. Six TonB-dependent microcins with different primary structures are processed and exported by highly homologous proteins. Three of these microcins are modified in an unknown way and they have in common specificity for catecholate siderophore receptors.

Amino Acid Sequence↗
PubMed1997

Slow negative brain potentials as reflections of specific modular resources of cognition.

The paper summarizes a series of experiments in which the topography and the amplitude of slow event-related brain potentials (slow ERPs) was studied in cognitive tasks which imposed different amounts of load on functionally distinct processing modules. The results suggest that the topography of slow ERPs reflects the relative activation/inactivation of distinct cortical cell assemblies while the absolute amplitude of the negative maximum seems to reflect how much a particular cell assembly is activated at a particular time. Translated into the terminology of cognitive resource theories one could say that tasks which evoke distinct slow wave patterns draw on independent resources. Likewise, the amplitude of a slow wave pattern could be related to the construct of resource allocation, i.e. the larger the amplitude of a slow wave pattern the more resources of a particular type are allocated to a task. These findings are discussed with respect to possible generator mechanism of slow waves and in relation to possible causes of capacity limitations of the human information processing system.

Brain↗
PubMed1997

Internal regulation of a modular system: the different faces of internal control.

The living cell houses a multitude of molecular processes that operate simultaneously in a mutually consistent fashion. A certain degree of organization stands out, e.g. in terms of the various metabolic pathways, transcription versus translation, signal transduction versus metabolism. This paper shows that by taking one of the aforementioned organizational principles into account, the complexity of understanding cell function quantitatively may be reduced significantly. To this aim the definition of the corresponding type of organization is refined and the conceptual tools used in the analysis of the control of cell function are adjusted. The approach is elaborated for a theoretical model of cell function, in which the latter depends on a constellation of interdependent but unconnected modules. The organization of a system is reduced to global control within a limited set of partaking modules and the links between them. Information about the systems total internal control and regulability is then drastically reduced to the information specifying global control and the regulability of the pathways that constitute the system. It is shown quantitatively how control at a lower level of organization bears on the control of the cell as a whole. The approach centers on writing the product of control (matrix) and elasticity (matrix) at a number of different levels of aggregation; these products equalling the identity (matrix) under different conditions. We demonstrate that there are at least three ways in which control and regulability of a system can be matched. In one, the true control within and between the modules of the systems is the inverse of the primary regulability (i.e. elasticity plus stoichiometry). In a second, the control internal to a module (but partly determined through the other modules) is matched by the inverse of newly defined 'global' regulabilities for each module separately, which comprise the regulatory impact of the remainder of the system. In the third, the regulabilities are the ones intrinsic to the module and the control is taken equal to the control that would reign in the absence of the regulatory interactions between the units. In making these distinctions, it becomes transparent how much control stems from control within the organizational modules, and how much derives from the regulatory interactions between them. Control through other modules turns out to be equivalent, at steady state, to control within a module. The implications of this type of cellular organization for the location of the steady-state operating point is discussed.

Animals↗
PubMed1999

The modularity of biological regulatory networks.

A useful approach to complex regulatory networks consists of modeling their elements and interactions by Boolean equations. In this context, feedback circuits (i.e. circular sequences of interactions) have been shown to play key dynamical roles: whereas positive circuits are able to generate multistationarity, negative circuits may generate oscillatory behavior. In this paper, we principally focus on the case of gene networks. These are represented by fully connected Boolean networks where each element interacts with all elements including itself. Flexibility in network design is introduced by the use of Boolean parameters, one associated with each interaction or group of interactions affecting a given element. Within this formalism, a feedback circuit will generate its typical dynamical behavior (i.e. multistationarity or oscillations) only for appropriate values of some of the logical parameters. Whenever it does, we say that the circuit is 'functional'. More interestingly, this formalism allows the computation of the constraints on the logical parameters to have any feedback circuit functional in a network. Using this methodology, we found that the fraction of the total number of consistent combinations of parameter values that make a circuit functional decreases geometrically with the circuit length. From a biological point of view, this suggests that regulatory networks could be decomposed into small and relatively independent feedback circuits or 'regulatory modules'.

Feedback↗
PubMed1998

Modular distribution of vasoactive intestinal polypeptide in the rat barrel cortex: changes induced by neonatal removal of vibrissae.

The distribution of vasoactive intestinal polypeptide-immunoreactive neuronal structures in the barrel cortex (posteromedial barrel subfield) of adult rats was analysed after unilateral removal of the vibrissal follicles of row C in neonatal rats. The hypothesis was tested whether the distribution of vasoactive intestinal polypeptide-immunoreactive structures depends on the normal anatomical organization of the specific sensory input. After three months survival the distribution of the vasoactive intestinal polypeptide-immunoreactive structures was morphometrically evaluated. This approach revealed alterations in the contralateral posteromedial barrel subfield, where the disappearance of barrel row C and a substantial increase in size mainly of barrel row D, but also of other rows could be detected. Increase in row D included both barrels and the interspace (septal segments between barrels in one row). As vasoactive intestinal polypeptide immunoreactivity of the barrel field was found previously to be localized in synaptic boutons involved in symmetric synapses, our present findings suggest that (i) the interspace is enriched in inhibitory vasoactive intestinal polypeptide-immunoreactive synapses as opposed to the excitatory thalamocortical input reaching the barrel hollow, (ii) the spatial distribution of the vasoactive intestinal polypeptide system in the barrel cortex is closely associated with the neuronal organization of the sensory input and reacts with a considerable plasticity to lesion-induced changes of the input, and (iii) the compensatory barrel hypertrophy in a row neighbouring the deafferented row involves an increasing number of vasoactive intestinal polypeptide-immunoreactive synapses per barrel.

Afferent Pathways↗
PubMed2002

Design and application of a new modular adapter for laser diffraction characterization of inhalation aerosols.

An inhaler adapter has been designed for the characterization of the aerosol clouds from medical aerosol generators such as nebulizers, dry powder inhalers (dpis) and metered dose inhalers (mdis) with laser diffraction technology. The adapter has a pre-separator, for separation of large particles (i.e. carrier crystals) from the aerosol cloud before it is exposed to the laser beam. It also has a fine particle collector for measuring the emitted mass fraction of fines by chemical detection methods after laser diffraction sizing. The closed system enables flow control through the aerosol generators and all test conditions, including ambient temperature and relative humidity, are automatically recorded. Counter flows minimize particle deposition onto the two windows for the laser beam, which make successive measurements without cleaning of these windows possible. The adapter has successfully been tested for nebulizers, mdis and dpis. In a comparative study with ten nebulizers it was found that these devices differ considerably in droplet size (distribution) of the aerosol cloud for the same 10% aqueous tobramycin solution (volume median diameters ranging from 1.25 to 3.25 microm) when they are used under the conditions recommended by the manufacturers. The droplet size distribution generated by the Sidestream (with PortaNeb compressor) is very constant during nebulization until dry running of the device. Comparative testing of dpis containing spherical pellet type of formulations for the drug (e.g. the AstraZeneca Turbuhaler) with the adapter is fast and simple. But also formulations containing larger carrier material could successfully be measured. Disintegration efficiency of a test inhaler with carrier retainment (acting as a pre-separator) could be measured quite accurately both for a colistin sulfate formulation with 16.7% of a lactose fraction 106-150 microm and for a budesonide formulation with a carrier mixture of Pharmatose 325 and 150 M. Therefore, it is concluded that, with this special adapter, laser diffraction may be a valuable tool for comparative inhaler evaluation, device development, powder formulation and quality control. Compared to cascade impactor analysis, laser diffraction is much faster. In addition to that, more detailed and also different information about the aerosol cloud is obtained.

Administration, Inhalation↗
PubMed1998

Modular component separation and reperfusion of abdominal aortic aneurysm sac after endovascular repair of the abdominal aortic aneurysm: a case report.

Transluminal placement of a stent graft in patients with an abdominal aortic aneurysm is a new endovascular technique that offers a potentially less invasive and less risky alternative to open surgery. Complications after stent graft placement are not infrequent, but in most cases secondary endovascular intervention is successful. We describe a late major leak in the aneurysmal sac caused by a distal migration of the iliac limb of a bifurcated graft. This late complication was successfully treated by covered stent placement, excluding and thrombosing completely the reformed aneurysm.

Aged↗
PubMed2000

Factors contributing to rapid wear and osteolysis in hips with modular acetabular bearings made of hylamer.

There have been several reports of osteolysis associated with rapid wear of Hylamer. A detailed analysis of retrieved implants and tissues can identify factors contributing to rapid wear and osteolysis. The mean linear wear rate of 12 liners was 0.49 mm/y, and 11 of 12 hips had progressive retroacetabular osteolysis. The average patient age was 50 years, and the mean implantation time was 50 months. All liners were sterilized by gamma irradiation in air. There was an 11-month difference in the average shelf-life of the 3 liners that were white and those that were darker in color. The volumetric wear rate of the white liners was 30% less than that of the others, suggesting a difference in the wear resistance of the liners as a function of shelf life. The mean average surface roughness (Ra) and the mean maximum surface roughness (R(max)) of the femoral heads were increased 3-fold and 50-fold compared with typical values for unused femoral heads. Evidence of 3-body wear, such as metal particles embedded in the liners, was commonly present. The pattern of backside liner deformation and burnishing was consistent with relative motion between the liner and the shell. In addition to generating Hylamer wear particles, repetitive axial motion between the liner and shell could generate fluid pressure, which transmitted through holes in the acetabular shell could cause or contribute to the development of retroacetabular osteolysis. Hylamer particles of variable shape and size, consistent with generation by several wear modes, were isolated from periprosthetic tissues.

Acetabulum↗
PubMed1995

Hybrid fixation modular tibial prosthesis. Early clinical and radiographic results and retrieval analysis.

A prosthetic tibial component has been designed with features for fixation to bone using a combination of acrylic cement and ingrowth interfaces. This hybrid concept affords the component the immediate stability of cement fixation and the potential long-term stability of biologic fixation. The ingrowth interfaces (coupled with the central stem) are intended to shield the cement interface beneath the tibial tray from the tensile liftoff forces that result from eccentric loading, while avoiding the fretting and osteolysis associated with screw fixation. A disassembly capability allows the tray to be removed from the stemmed anchorage assembly, facilitating component extraction and limiting bone loss. A clinical and radiographic review of 50 consecutive primary total knee arthroplasties with a mean follow-up period of 35 months revealed stable interfaces with no progressive radiolucencies and minimal remodeling changes. The mean Knee Society knee score was 92.2. At final follow-up evaluation, 88.6% of patients noted no or mild (occasional) pain. Retrieval of three prosthetic knees with chronic sepsis showed extensive ingrowth into the porous interfaces and an osteointegrated bony sleave around the smooth central stem.

Adult↗
PubMed2001

Modularity, evolution, and the binding problem: a view from stability theory.

Any biological object, and specifically the brain, is the result of evolution. Evolution proceeds by accumulation and combination of stable intermediate states-as is well known, survival of the fittest really means survival of the stable. Simple examples abound: for instance, human emotional response involves both a fast archaic loop bypassing the cortex, and a slower cortical loop; motion control architecture in vertebrates is believed to involve combinations of simple motor primitives. However, in themselves, accumulations and combinations of stable elements have no reason to be stable. Hence the hypothesis that evolution will favor a particular form of stability, which automatically guarantees stability in combination. Such a form of stability, which we refer to as 'contraction,' can be characterized mathematically. Thus, contraction theory may help guide functional modeling of the central nervous system, and conversely it provides a systematic method to build arbitrarily complex robots out of simpler elements. Furthermore, contraction theory may shed light on the problem of perceptual unity (binding problem) by providing simple models and conditions for the overall convergence of a large number of specialized processing elements connected through networks of feedback loops.

Biological Evolution↗
PubMed1999

Organization of face and object recognition in modular neural network models.

There is strong evidence that face processing in the brain is localized. The double dissociation between prosopagnosia, a face recognition deficit occurring after brain damage, and visual object agnosia, difficulty recognizing other kinds of complex objects, indicates that face and non-face object recognition may be served by partially independent neural mechanisms. In this paper, we use computational models to show how the face processing specialization apparently underlying prosopagnosia and visual object agnosia could be attributed to (1) a relatively simple competitive selection mechanism that, during development, devotes neural resources to the tasks they are best at performing, (2) the developing infant's need to perform subordinate classification (identification) of faces early on, and (3) the infant's low visual acuity at birth. Inspired by de Schonen, Mancini and Liegeois' arguments (1998) [de Schonen, S., Mancini, J., Liegeois, F. (1998). About functional cortical specialization: the development of face recognition. In: F. Simon & G. Butterworth, The development of sensory, motor, and cognitive capacities in early infancy (pp. 103-116). Hove, UK: Psychology Press] that factors like these could bias the visual system to develop a processing subsystem particularly useful for face recognition, and Jacobs and Kosslyn's experiments (1994) [Jacobs, R. A., & Kosslyn, S. M. (1994). Encoding shape and spatial relations-the role of receptive field size in coordination complementary representations. Cognitive Science, 18(3), 361-368] in the mixtures of experts (ME) modeling paradigm, we provide a preliminary computational demonstration of how this theory accounts for the double dissociation between face and object processing. We present two feed-forward computational models of visual processing. In both models, the selection mechanism is a gating network that mediates a competition between modules attempting to classify input stimuli. In Model I, when the modules are simple unbiased classifiers, the competition is sufficient to achieve enough of a specialization that damaging one module impairs the model's face recognition more than its object recognition, and damaging the other module impairs the model's object recognition more than its face recognition. However, the model is not completely satisfactory because it requires a search of parameter space. With Model II, we explore biases that lead to more consistent specialization. We bias the modules by providing one with low spatial frequency information and the other with high spatial frequency information. In this case, when the model's task is subordinate classification of faces and superordinate classification of objects, the low spatial frequency network shows an even stronger specialization for faces. No other combination of tasks and inputs shows this strong specialization. We take these results as support for the idea that something resembling a face processing "module" could arise as a natural consequence of the infant's developmental environment without being innately specified.

Journal Article↗