bluuebunny/crossref_metadata_2025 huggingface dataset:
Integration Site Selection by the
Bacteroides
Conjugative Transposon CTnBST
Authors: Song Bo , Shoemaker Nadja B. , Gardner Jeffrey F. , Salyers Abigail A.
Published: July 2007

A newly discovered
Bacteroides
conjugative transposon (CTn), CTnBST, integrates more site specifically than two other well-studied CTns, the
Bacteroides
CTn CTnDOT and the enterococcal CTn Tn
916
. Moreover, the integrase of CTnBST, IntBST, had the C-terminal 6-amino-acid signature that is associated with the catalytic regions of members of the tyrosine recombinase family, most of which integrate site specifically. Also, in most of these integrases, all of the conserved amino acids are required for integration. In the case of IntBST, however, we found that changing three of the six conserved amino acids in the signature, one of which was the presumed catalytic tyrosine, resulted in a 1,000-fold decrease in integration frequency. Changes in the other amino acids had little or no effect. Thus, although the CTnBST integrase still seems to be a member of the tyrosine recombinase family, it clearly differs to some extent from other members of the family in its catalytic site. We also determined the sequence requirements for CTnBST integration in the 18-bp region where the crossover occurs preferentially during integration. We found that CTnBST integrates in this preferred site about one-half of the time but can also use other sites. A consensus sequence was tentatively derived by comparison of a few secondary sites: AATCTGNNAAAT. We report here that within the consensus region, no single base change affected the frequency of integration. However, 3 bp at one end of the consensus sequence (CTG) proved to be essential for integration into the preferred site. This sequence appeared to be at one end of a 7-bp crossover region, CTGNNAA. The other bases could vary without affecting either integration frequency or specificity. Thus, in contrast to well-studied site-specific recombinases which require homology throughout the crossover region, integration of CTnBST requires homology at one end of the crossover region but not at the other end.
Simultaneous Catabolite Repression between Glucose and Toluene Metabolism in
Pseudomonas putida
Is Channeled through Different Signaling Pathways
Authors: del Castillo Teresa , Ramos Juan L.
Published: July 2007

Pseudomonas putida
KT2440(pWW0) can use toluene via the TOL plasmid-encoded catabolic pathways and can use glucose via a series of three peripheral chromosome-encoded routes that convert glucose into 6-phosphogluconate (6PG), namely, the glucokinase pathway, in which glucose is transformed to 6PG through the action of glucokinase and glucose-6-phosphate dehydrogenase. Alternatively, glucose can be oxidized to gluconate, which can be phosphorylated by gluconokinase to 6PG or oxidized to 2-ketogluconate, which, in turn, is converted into 6PG. Our results show that KT2440 metabolizes glucose and toluene simultaneously, as revealed by net flux analysis of [
13
C]glucose. Determination of glucokinase and gluconokinase activities in glucose metabolism, gene expression assays using a fusion of the promoter of the Pu TOL upper pathway to ′
lacZ
, and global transcriptomic assays revealed simultaneous catabolite repression in the use of these two carbon sources. The effect of toluene on glucose metabolism was directed to the glucokinase branch and did not affect gluconate metabolism. Catabolite repression of the glucokinase pathway and the TOL pathway was triggered by two different catabolite repression systems. Expression from Pu was repressed mainly via PtsN in response to high levels of 2-dehydro-3-deoxygluconate-6-phosphate, whereas repression of the glucokinase pathway was channeled through Crc.
Regulation of cGMP-dependent protein kinase-mediated vasodilation by hypoxia-induced reactive species in ovine fetal pulmonary veins
Authors: Negash Sewite , Gao Yuansheng , Zhou Weilin , Liu Jie , Chinta Shashi , Raj J. Usha
Published: July 2007

We previously reported that hypoxia attenuates cGMP-dependent protein kinase (PKG)-mediated relaxation in pulmonary vessels ( Am J Physiol Lung Cell Mol Physiol 279: L611–L618, 2003). To determine whether hypoxia-induced reactive oxygen and nitrogen species (ROS and RNS, respectively) may be involved in the downregulation of PKG-mediated relaxation, ovine fetal intrapulmonary veins were exposed to 4 h of normoxia or hypoxia, with or without scavengers of ROS [ N-acetylcysteine (NAC)] or peroxynitrite (quercetin and Trolox) and preconstricted with endothelin-1. Hypoxia decreased the relaxation response to 8-bromo-cGMP, PKG protein expression, and kinase activity and increased tyrosine nitration in PKG. However, ROS and RNS scavengers prevented these changes. To determine whether increased PKG nitration diminishes PKG activity, pulmonary vein smooth muscle cells (PVSMC) were exposed to shorter-term (30 min) hypoxia, which increased PKG nitration and decreased PKG activity but did not alter PKG protein expression. Increased dihydro-2,7-dichlorofluorescein diacetate (DCFH2-DA) fluorescence in PVSMC after 4 h or 30 min of hypoxia was not observed in the presence of NAC, quercetin, or Trolox, suggesting increased ROS and RNS production. Increased PKG nitration and the associated decrease in PKG activity in PVSMC after 30 min of hypoxia were also reversed on reoxygenation. The consequences of PKG nitration were assessed by exposure of purified PKG-Iα to peroxynitrite, which caused increased 3-nitrotyrosine immunoreactivity and inhibition of kinase activity. Our data suggest that, after 30 min of hypoxia, reversible covalent modification of PKG by hypoxia-induced reactive species may be an important mechanism by which the relaxation response to cGMP is regulated. However, after 4 h of hypoxia, PKG nitration and decreased PKG expression are involved.
An Existential-Dialectical-Phenomenological Approach to Understanding Cultural Tilts: Implications for Multicultural Research and Practice
Authors: Hannush Mufid James
Published: July 2007

An existential-dialectical-phenomenological approach is applied to the understanding of the universal tensions between multicultural and transcultural value-laden modalities of existence. Differences in cultural comportments are described as variations in local human ways in dealing with universal and bipolar existential modalities, values, or needs, such as freedom versus limitation, independence versus (inter)dependence, and connectedness versus separateness. Cultures are described as being organized around and as providing their members with ways of dealing with these value-laden dialectical dilemmas. Cultures are further depicted as legitimating one dialectical pole to the detriment of the other dialectical pole. Some cultures, for example, legitimate the dialectical poles of freedom, independence, and separateness, while deemphasizing or denying the dialectical poles of limitation, (inter)dependence, and connectedness. Other cultures legitimate the opposite. These one-sided value orientations of cultures are referred to as cultural tilts. The implications for the practice of multicultural counseling and phenomenologically-based qualitative research are delineated.
The Multitude and the Kangaroo: A Critique of Hardt and Negri's Theory of Immaterial Labour
Authors: Camfield David
Published: July 2007

Hardt and Negri's theory of immaterial labour provides a socio-economic foundation in the contemporary world for the philosophical and political elements of their thought. Although there has been considerable engagement with Hardt and Negri's work, the socio-economic dimension of their thought has received little sustained attention. This is certainly true of their theory of immaterial labour. This article aims to remedy this oversight. It presents and scrutinises Hardt and Negri's concept of immaterial labour and its putative hegemony. It then examines the depiction of the world of paid work in advanced capitalist societies with which the theory is associated and looks at three alleged consequences of the rise of immaterial labour. It concludes that this dimension of Hardt and Negri's thought is profoundly flawed, that immaterial labour cannot play the role they wish to assign it in their theory, and that this failure suggests the importance of a different method of developing theory from that employed by Hardt and Negri, along with so many other contemporary writers.
Induction of P-glycoprotein expression and activity by ritonavir in bovine brain microvessel endothelial cells
Authors: Perloff Michael D , von Moltke Lisa L , Fahey Jeanne M , Greenblatt David J
Published: July 2007

Extended treatment with human immunodeficiency virus (HIV) protease inhibitors (HPIs) is standard in HIV/AIDS therapy. While these drugs have helped decrease the overall incidence of AIDS defining illnesses, the relative prevalence of HIV/AIDS dementia has increased. HPIs may cause induction of blood-brain barrier (BBB) drug transporters (P-glycoprotein; P-gp) and thereby limit entry of HPIs into brain tissue, increasing the probability that the brain could become an HIV sanctuary site. Using bovine brain microvessel endothelial cells (BMEC) as an in-vitro model of the BBB, the potential for the HIV protease inhibitor ritonavir to cause induction of P-gp activity and expression was examined. BMEC were isolated from fresh cow brain by enzymatic digest and density centrifugation. Primary culture BMEC were co-incubated with ritonavir or vehicle control for 120 h. Quantitative drug accumulation of rhodamine 123 (Rh123) and fluorescence microscopy were used as measures of P-gp activity. P-gp expression was assessed using quantitative Western blotting. Ritonavir decreased Rh123 cell accumulation and increased P-gp immunoreactive protein in a concentration-dependent manner. Fluorescent microscopy mirrored Rh123 quantitative studies. In BMEC pretreated with 30 μM ritonavir, Rh123 accumulation was decreased 40% and immunoreactive P-gp protein increased 2-fold. Collectively, a strong correlation between decreased Rh123 BMEC accumulation and increased P-gp immunoreactive protein was observed (Spearman r2 = 0.77, P < 0.0001). Thus extended exposure of BMEC to ritonavir caused a concentration-dependent increase in P-gp activity and expression. Similar findings may occur at the clinical level with prolonged HIV protease inhibitor use, giving insight into the central nervous system as an HIV sanctuary site and eventual development of HIV dementia.
Protective effect of total flavonoids fromBidens bipinnataL. against carbon tetrachloride-induced liver injury in mice
Authors: Zhong Ming-mei , Chen Fei-hu , Yuan Li-ping , Wang Xiao-hua , Wu Fan-rong , Yuan Feng-lai , Cheng Wen-ming
Published: July 2007

Bidens bipinnata L. is well known in China as a traditional Chinese medicine. This study was designed to evaluate the hepatoprotective activity of the total flavonoids of B. bipinnata L. (TFB) against carbon tetrachloride (CCI4)-induced acute liver injury in mice and to determine its mechanism of action. Oral administration of TFB at doses of 50, 100 and 200 mg kg−1 for 7 days significantly reduced the elevated relative values of liver weight, serum transaminases (alanine aminotransferase and aspartate aminotransferase) and the hepatic morphologic changes induced by CCl4 in mice. In addition, TFB markedly inhibited CCl4-induced lipid peroxidation and enhanced the activity of the antioxidant enzymes superoxide dismutase and glutathione peroxidase. Moreover, pretreatment with TFB suppressed nitric oxide production and nuclear factor-kB activation in CCl4-treated mice. The results suggest that TFB has significant hepatoprotective activity and its mechanism is related, at least in part, to its antioxidant properties. Further research is required to investigate the detailed mechanism of the protective effect of TFB on acute liver injury.
Sphingosine 1-phosphate (S1P) induces shape change in rat C6 glioma cells through the S1P2 receptor: development of an agonist for S1P receptors
Authors: Kim Kyeok , Kim Yu-Lee , Sacket Santosh J , Kim Hyo-Lim , Han Mijin , Park Deok Seong , Lee Baeck Kyoung , Lee Won Koo , Ha Hyun-Joon , Im Dong-Soon
Published: July 2007

Treatment with isoprenaline led to a change in the cell morphology of rat C6 glioma cells. This morphological change was reverted by the addition of sphingosine 1-phosphate (S1P). Using this morphological change as a response marker we determined that DS-SG-44 ((2S,3R)-2-amino-3-hydroxy-4-(4-octylphenyl)butyl phosphoric acid) was an agonist of S1P receptors. The DS-SG-44-induced morphological reversion was not observed with such structurally related molecules as DS-SG-45 ((2S,3R)-2-amino-3-hydroxy-4-(3-octylphenyl)butyl phosphoric acid) and DS-SG-12 ((2S,3R)-2-amino-4-(4-octylphenyl)butane-1,3-diol). The S1P- and DS-SG-44-induced shape changes were nseither reproduced with the S1P1/S1P3 receptor agonist VPC24191 nor inhibited by the S1P1/S1P3 receptor antagonist, VPC23019. Transfection with small interfering RNA (siRNA) for the S1P2 receptor greatly inhibited the DS-SG-44-induced shape change, and in part an S1P-induced response. In the presence of VPC23019, siRNA transfection for the S1P2 receptor almost completely blocked the S1P- and DS-SG-44-induced shape changes. Our results suggested that DS-SG-44, a newly-synthesized S1P analogue, acted as an S1P receptor agonist and that the S1P-induced shape change in rat C6 glioma cells was mediated mainly through the S1P2 receptor, and cooperatively through the S1P1/S1P3 receptors.
On the evaluation of stress and contact force in a beam due to a prescribed deflection, taking into account the change of secant modulus
Authors: Wing-Chau Fok
Published: July 2007

A procedure to calculate the stress and contact force in a beam taking into account of the change of elastic modulus of the material is outlined. Making use of published data, the mathematical relationship of the secant modulus and applied stress is found. The stress and contact force can be calculated directly from a closed form expression.
Photoelastic investigation of stresses at an oblique hole in a thick flat plate under uniform uniaxial tension
Authors: Stanley P , Day B V
Published: July 2007

The magnitudes and positions of the principal stress indices at a series of isolated oblique holes in thick, wide plates subjected to uniaxial tension have been determined using the photoelastic frozen-stress technique. The model series covered nominal plate thickness to hole diameter ratios of 1.33, 2.0, and 3.0, hole obliquity angles of 0, 15, 30, 45, and 60 degrees, and applied load directions of 0, 30, 60, and 90 degrees relative to the major axis of the surface ellipse. The results are discussed in detail and compared with other independent values available in the literature.
A simple approximation for the stress intensity factor of a crack at a notch
Authors: Yates J R
Published: July 2007

A simple procedure for estimating the stress intensity factor of a continuous crack at the root of a circumferential notch in a round bar is presented. Numerical solutions for equivalent notched and un-notched geometries are compared. The resulting correction term for notches is formulated as a polynomial equation using only notch geometric parameters and is used in conjunction with the conventional stress intensity calibration for the un-notched configuration.
Static analysis of short beams
Authors: Hardy S J , Pipelzadeh M K
Published: July 2007

The finite element method has been used to obtain elastic stress data for simply-supported short beams with uniformly distributed loading and short built-in beams subjected to shear displacement (referred to as ‘sinking beams’). Length-to-depth ratios in the range 0.5–2.0 have been considered. In the case of the simply-supported beam, some results are compared with published data, while additional information on section warping and stress contours is presented. Similar results are presented for the sinking beam, for which alternative solutions are not currently published. Predictions are compared with estimates using simple theory for slender beams and modified theories which include transverse shear effects. It is apparent that these estimates can be significantly in error when length-to-depth ratios are less than 2.0.
A parametric failure criterion for paperboard material
Authors: Labossière P , Neale K W
Published: July 2007

After a brief review of failure criteria for anisotropic materials, a new parametric failure criterion for fibre-reinforced laminae under plane stress loading conditions is presented. Using previously published experimental data for paper-board, it is shown that this criterion can lead to an improved correlation between experimental data and analytical failure envelopes for this material.
Bending of cross-ply laminated plates with matrix cracks
Authors: Makins R K , Adali S
Published: July 2007

A bending analysis is presented for cross-ply laminates containing matrix cracks. The cracks are modelled as aligned slit cracks across the ply thickness and transverse to the laminate plane. The distribution of cracks is assumed to be statistically homogeneous corresponding to an average crack density. The results are given for symmetrically and antisymmetrically laminated plates with a given density of matrix cracks. The effect of reduction in the laminate stiffness is studied by plotting the ratio of the centre deflection of cracked and uncracked laminates against the aspect ratio, crack density, and relative layer thicknesses. It is observed that the amount of increase in the plate deflection depends on the stacking sequence as well as on the relative thicknesses of layers.
The influence of the variation in wall thickness of glass fibre reinforced plastic pipe bends subjected to in-plane bending
Authors: Kitching R , Hose D R
Published: July 2007

Glass reinforced plastic (GRP) pipe bends as used in the process plant industry are often made by hand lay-up and, because of overlapping of layers in the construction, are prone to thickness variations sometimes approaching ± 50 percent of the mean thickness. An existing Fourier series analysis for calculating flexibility factors and strain distributions in such components with constant thickness subjected to in-plane bending moments is extended to include typical thickness variations. Results are expressed in closed form, and their practical implications are discussed. The theoretical results are also discussed in relation to experiments on two GRP pipe bends having nominal inside pipe diameters of 250mm and mean pipe radii of 250mm where the resin was polyester and the E-glass reinforcement consisted of three layers of 0.6 kg m−2 chopped strand mat and one layer of 0.6kg m−2 woven rovings.
Finite deformation of compressible bonded rubber mounts
Authors: Petrie C J S , Shariff M H B M
Published: July 2007

Bearings for bridges, earthquake isolation bearings for buildings, and elements in vehicle suspensions may be made from one or more layers of elastomer between rigid steel plates to which the elastomer is bonded. Using simplifying assumptions based on previous work, simple and explicit forms of solution are developed for finite (non-linear) deformation of bonded blocks, in plane or axisymmetric strain, with special reference to compressible elastic materials. The qualitative behaviour of the explicit form of solution is reasonable and on linearizing it agrees with published experimental and theoretical results for small deformation. The explicit form of solution also compares well with such experimental results as are available for finite deformation and with finite element calculations. Application of the results to laminated blocks, where compressibility is expected to be important is illustrated, and an assessment of the effect of the bulk compressibility of the rubber is offered.
Free bending characteristics of sheathed spiral strands under cyclic loading
Authors: Raoof M , Huang Y P
Published: July 2007

A theoretical insight is given into the non-linear free bending characteristics of axially preloaded and large diameter sheathed spiral strands experiencing high external hydrostatic pressure in, for example, deep water floating platform applications.

The theoretical model takes geometrical non-linearities and interwire friction fully into account. It is capable of estimating variations of strand plane-section bending stiffness, ( EI)eff, and hysteresis as a function of the imposed radius of curvature, magnitude of the external pressure, and level of mean axial load.

An oversight in a previously reported analytical model for following the reductions in strand flexural rigidity due to interlayer slippage has also been identified and subsequently corrected. In addition, the corrected model (which assumed small deflections) has been extended to cover geometrical non-linearities due to changes in lay angle and helix radius.

Numerical results are presented for a large diameter (102 mm OD) sheathed spiral strand experiencing various levels of mean axial load and external pressure. In particular, it is shown that under the plane-section bending assumption, the upper and lower bounds to ( EI)eff are, for all practical purposes, independent of the magnitude of mean axial load and external pressure. Moreover, the maximum possible values of radii of curvature associated with which plane-section bending is possible, have been identified in all cases. It is believed that even in the presence of interlayer slippage, the damping model (which is based on plane-section bending) offers reasonable and useful lower bounds to a strand's specific damping which should prove of value in certain applications involving cable dynamics.
Weight functions for curved crack fronts using bem
Authors: Bains R , Aliabadi M H , Rooke D P
Published: July 2007

This paper presents an efficient numerical weight function technique, based on the boundary element method, for the determination of stress intensity factors of curved crack fronts in three-dimensional finite bodies. The weight functions are based on the notion of fundamental fields, which are defined from point loads acting at the crack front. A regularization procedure that incorporates the fundamental fields of the penny-shaped crack in an infinite elastic body is used to obtain weight functions for a penny-shaped edge crack in a cylindrical bar. Stress intensity factors for elliptical crack fronts can be generated by employing the properties of the fundamental fields at the load points on the crack front.

Stress intensity factor variations along the crack-fronts are presented when these finite cracked geometries are subjected to various loads that produce mode I deformation of the crack faces. Wherever possible, solutions are compared with values published in the literature and are found to be in good agreement.
A review of the determination of energy release rates for strips in tension and bending. Part II – dynamic solutions
Authors: Williams J G
Published: July 2007

Energy release rate calculations are performed for a flexible strip peeling from a substrate and including the effects of kinetic energy. The effects of various wave speeds are demonstrated. Solutions for an axially loaded strip are then explored, including the transient solutions and those for steady-state conditions. The methods developed are then used for cases involving the bending of strips, including those of moving loads. It is demonstrated that these methods of analysis are of value in the analysis of test specimens and of use in design.
On the creep of ferritic weldments containing multiple zones in plates under uniaxial loading
Authors: Craine R E , Hawkes T D
Published: July 2007

Weldments are not currently included in most high temperature design codes although welds are known to be life-limiting. Metallurgists state that there are four principal regions in a ferritic weldment with the parent metal and weld region being separated by both the narrow high temperature heat affected zone (HAZ) and the narrow lower temperature type IV region. Expected weld performance can be evaluated using full size weldment testing or by the simpler creep testing of cross-weld specimens in the laboratory. The former is expensive but the latter, although cheaper to carry out, is not well understood. To improve understanding of the failure process in weldments, a plate containing these four distinct weldment regions and subjected to a constant uniaxial tensile end loading is studied in this paper. The plate is modelled using the Cosserat theory of plates and a generalization of the steady state Norton creep law and numerical solutions of the governing differntial equations are obtained illustrating how the creep strain rate is changed by variations in the widths and strengths of the type IV, HAZ, and weld regions and by varying the creep index. These results reveal that when narrow zones exist in a ferritic weldment the strain rate at a point can be greatly affected by the properties of both the neighbouring regions and non-adjacent zones and, therefore, deductions made through using only the homogeneous strengths of the constitutent materials would usually be incorrect.
Stress analysis for a lug under various conditions
Authors: Wang G S
Published: July 2007

Stress analyses are performed using the finite element method (FE) for a lug under various conditions. The effects of the clearance between pin and hole, the pin load magnitude, the contact condition, and the relative pin/lug rigidities etc. are investigated. The effect of some durability improvement techniques, such as interference fitting, bushing, and cold working are also investigated. Significant results are obtained which can improve both the understanding of the stress state in a lug and the design of a durable lug.
The use of model materials to simulate creep behaviour
Authors: Fessler H , Hyde T H
Published: July 2007

The objective of this paper is to show that there are model materials which can be used to develop better assumption to improve theories, to verify the applicability of theories, or to get creep information which is otherwise unobtainable.

The mechanical properties necessary to characterize non-linear component behaviour are defined and presented for some chill-cast lead alloys at 20°C. When normalized, they are shown to be sufficiently similar to structural steels to allow the prediction of prototype response from model tests. This paper also describes the methods used to make lead alloy models for the experimental study of creep of components.
Design and assessment of components subjected to creep
Authors: Ainsworth R A , Budden P J
Published: July 2007

The R5 procedure for assessing the high-temperature response of structures is described and recent progress highlighted. The scope and methodology of R5 are compared with those of existing and proposed high-temperature design codes. For defect-free components, R5 provides a shakedown approach intermediate between the elastic and inelastic routes in codes. As the codes give interaction diagrams based on shakedown concepts for particular loading circumstances, the R5 approach may be considered a generalization of existing methods. For defective components, the Reference stress methods recommended in R5 are described. Proposals for the incorporation of similar approaches in other codes are currently being considered, and these are also described.
An analysis of the symmetric rolling of aluminium strips using a three-dimensional elastic—plastic large deformation finite element method
Authors: Lin Z C , Huang C J
Published: July 2007

This study focuses on the deformation which occurs in three-dimensional elastic-plastic aluminium strips when they undergo symmetric rolling with a rigid body roller. This research is based on the theory of large deformation and large strain, using the updated Lagrangian formulation (ULF) and the incremental method to develop the analysis model of the three-dimensional elastic-plastic characteristic of aluminium strip rolling.

As for the determination of the direction of tangential friction force, this study also develops a modification algorithm to adjust to the three-dimensional rolling process. In addition, another rule is devised to identify the neutral point in order to further develop the theoretical model and computer program for the large deformation finite element method with the two-order strain rate equation.

Finally, this study uses the numerical analysis model developed in this research to simulate the deformation which occurs in aluminium strips when they undergo symmetric rolling, and the variation of rolling force. The research also compares the average rolling force of simulated cold rolling with experimental results. The results verify that the author's model is acceptable.
Experimental stress intensity factors for cracks in a thin plate with stiffeners
Authors: Nurse A D , Güng S , Patterson E A
Published: July 2007

The problem of cracked plates stiffened by three-dimensional stringers is investigated using transmission photoelasticity. Models were produced of the hole-in-the-plate geometry stiffened by a combination of stringers transverse and/or parallel to the applied tensile load. Cracks of different lengths emanating from one edge of the hole and approaching a stringer were examined. These cases represent geometry and loading conditions for which it would normally be very difficult to obtain results using analytical methods. The stringer-stiffened plates show a consistent reduction in the non-dimensional stress intensity factor of about 20 per cent irrespective of the arrangement of stringers.
Elastic-plastic finite element analysis of short flat bars with projections part 3: Combined axial and shear loading
Authors: Hardy S J , Pipelzadeh M K
Published: July 2007

This paper describes the results of a study of the elastic-plastic behaviour of short flat bars with projections subjected to combined steady axial and monotonic and cyclic shear loading using finite element analysis. The results are complementary to similar results for (a) shear loading and (b) axial loading. Six geometries are considered and elastic-plastic stress and strain data for both local and remote restraints are presented. A simple bilinear elastic-plastic material model is assumed and the results are normalized with respect to material properties so that they can be applied to geometrically similar components made from other materials which can be represented by the same material models.
Numerical study of some approaches to shape design sensitivity analysis using boundary elements
Authors: Tai K , Fenner R T
Published: July 2007

A numerical study is made of analytical differentiation (AD) and finite difference (FD) approaches to the computation of sensitivity derivatives required in shape design optimization problems. Based on the boundary element method for linear elastostatics, numerical solutions for response and sensitivity analysis are illustrated for the AD technique and the FD schemes with different step sizes. By solving the problem of an annular disc under internal pressure (for which analytical solutions are available), an indication of the absolute level of accuracy achievable by the FD procedure can be obtained. As there are advantages in using the FD technique for shape optimization, it is desirable to check its accuracy and effectiveness compared to the AD approach. An optimization problem based on the annular disc is then formulated and solved using the various analytical, AD and FD sensitivity values to show how the differing accuracies of the derivatives will affect the efficiency and performance of the optimization process, and whether the FD values used are sufficiently accurate for converging upon the correct optimum solution.
Local government structure as a spatial framework for rural development in Nigeria
Authors: Akpan Philip A.
Published: July 2007

Rural development has attracted attention from many quarters. The present administration in Nigeria is particularly anxious to bring it about in the shortest time possible. But most of the discussions of rural development tend to neglect the vital link between it and administrative structure. This paper therefore stresses the role which an appropriate administrative arrangement can play in bringing about rural development. The paper reviews the various efforts that Nigeria has made since 1950 to derive a suitable local administrative structure. It focuses on the 1976 reform and shows how it has failed to provide a suitable spatial framework for rural development. Based on the experiences of the past and the realities of the present, some principles are put forward as guidelines for an effective local administrative structure. Finally, an administrative arrangement which is development oriented and comprehensive enough to cater for the interest of all communities is proposed.
State intervention, contradictions and agricultural stagnation in Tanzanian—Cashew nut vs charcoal production
Authors: Nindi B. C.
Published: July 2007

The article first describes Tanzanian development ideology and main economic activities. It explains economic decline and gives a brief description of Rufiji District. The next section examines the dynamics of state‐peasant‐commercial class relationship in Rufiji district within the wider context. There is a number of broad theoretical lines of reasoning that have come to predominate in contemporary debate on the origins and genesis of the African agricultural crisis and Tanzania in particular. This paper seeks to show that the notion of crisis must be subject to a careful, specific, and historically sensitive analysis.
Urban local government finance in Nigeria: The case of Onitsha local government
Authors: Olowu Dele
Published: July 2007

Onitsha, located along the route that connects south‐western and south‐eastern Nigeria, has a very financially dynamic local government. Over one‐quarter of the total revenues of this local government come from its market and motor parks. This is an unusual source for a local government that has perhaps the largest per capita revenue in Nigeria—almost N40, compared with the national average of N4.9. The procedure for collecting this revenue is regarded as highly successful since there is greater reliance on the citizens than tax officials. The volume of revenues collected has allowed the council maintain a large surplus revenue over a long period of time, which enables it to carry out important programmes of primary and adult education. It is also beginning to develop its property revenue collection system in collaboration with the Anambra State government.
Small town local government finance in Kenya: The case of Karatina Town Council
Authors: Smoke Paul
Published: July 2007

In a country where local governments are plagued by numerous problems and are under frequent attack from national politicians and the central government, Karatina Town Council stands out as one of the few local authorities widely considered to be doing a highly effective job. This paper reviews the organization and functions of Kenyan local authorities and highlights major constraints on their performance. Some background information on Karatina Town Council is presented, followed by documentation of the council's superior performance and an analysis of the factors that seem to contribute to Karatina's success.
Rural local government finance in Kenya: The case of Murang'a County Council
Authors: Smoke Paul
Published: July 2007

The Murang'a County Council is recognized in Kenya as one of the country's most effective rural local authorities. Compared to other county councils, Murang'a raises substantial revenues and provides a wide variety of services. This case study presents some background on the local economy of Murang'a District, details available information about the county council's excellent fiscal performance, and highlights some of the major factors behind the effectiveness of Murang'a in resource mobilization and service delivery.
Decentralization by default: Local governance and the view from the village in The Gambia
Authors: Davis Daniel , Hulme David , Woodhouse Philip
Published: July 2007

Policies to decentralize government activities in The Gambia have been on the agenda for more than a decade but no decisions have been taken. During this period the quality of government services to rural areas has declined dramatically. The linchpin of provincial administration, the divisional commissioner, has become redundant as far as development is concerned. The activities of line ministries have deteriorated as their expenditures have been reduced and they lack the funds to permit staff to operate at village level. Area councils that were previously regarded as wasteful are now totally discredited. Village development committees (VDCs) have been formed, but the results are mixed and often they are ineffective. By default, decentralization in the 1980s and early 1990s in The Gambia has been achieved by non‐governmental organizations (NGOs), which have rapidly grown in number and significance. This article explores the perceptions of villagers in The Gambia about the various organizations that are meant to serve their needs. Its conclusion speculates on proposals to implement a new decentralization policy in the country and points to the need for aid agencies to adopt a less simplistic approach to the issue of local governance.
Field Equations in Quantum Electrodynamics
Authors: Brandt Richard A.
Published: July 2007

A formulation of quantum electrodynamics is presented, based on finite local field equations. These Dirac and Maxwell equations have the usual form except that the current operators f(x) and jμ (x) are explicitly expressed as local limits of sums of non‐local field products and suitable subtraction terms. These limits are shown to exist and to yield finite operators in the sense that the iterative solutions to the field equations are equivalent to conventional renormalized perturbation theory. The various invariance properties of the theory, including Lorentz invariance, gauge invariance, charge conjugation invariance, and renormalization invariance, are discussed and related directly to the field equations and current definitions. Initially only the general forms of the currents, based on dimensional arguments, are given. The electric current, for example, contains the (suitably defined) term :A3(x) :.The corresponding field equations are used to derive renormalized Dyson‐Schwinger‐type integral equations for the renormalized proper part functions ∑, IIμν, Λμ, and Xαβγδ (the four‐photon vertex function), etc. Application of the boundary conditions ∑(p̀ = m) = ∑′(p̀ = m) = II(O) = II′(O) = II″(O) = Λ(p̀ = m, o) = X(O, O, O, O) = O completely specifies the current operators. Consistency is established by deriving the same equations from rigorous renormalization theory so that their iterative solutions are proved to reproduce the correct renormalized perturbation expansion.

The electric current operator is exhibited in a manifestly gauge invariant form and in a form which is manifestly negative under charge conjugation. It is shown, in fact, that much of jμ (x) can be determined directly from the requirements of gauge invariance and charge conjugation covariance, without recourse to the integral equations. It is suggested that equal time commutation relations can serve to similarly specify the rest of the current.
Furry Picture for Quantum Electrodynamics with Pair‐Creating External Field
Authors: Fradkin E. S. , Gitman D. M.
Published: July 2007

In the paper the perturbation theory is constructed for QED, for which the interaction with the external pair‐creating field is kept exactly. An explicit expression for the perturbation theory causal electron propagator is found. Special features of usage of the unitarity conditions for calculating the total probabilities of radiative processes in the case are discussed. Exact Green functions are introduced and the functional formulation is discussed. Perturbation theory for calculating the mean values of the Heisenberg operators, in particular, of the mean electromagnetic field is built in the case under consideration. Effective Lagrangian which generates the exact equation for the mean electromagnetic field is introduced. Functional representations for the generating functionals introduced in the paper are discussed.
Hadronic Production of Heavy QQ Bound States
Authors: Escobar C. O. , Malbouisson A. P. C. , Santoro A. F. S. , Shellard R. C. , Souza M. H. G.
Published: July 2007

Several mechanisms for the production of heavy QQ bound states are reviewed. A systematic comparison between model predictions and experimental results is presented. The various theoretical and experimental uncertainties are discussed.
Pion Coupling to Nuclei
Authors: Dumbrajs Olgierd
Published: July 2007

The concept of the pion‐nucleus coupling constants is discussed. Methods of their determination are reviewed. These include: forward dispersion relations, extrapolation of differential cross sections to the poles in the angular variable, analysis of data on electromagnetic form factors with the use of the PCAC and CVC hypotheses, pion photoproduction at threshold and low‐ernergy theorems. Our present knowledge of the pion coupling to the He, Li, Be, C, N and O nuclei is summarized.
Dielectric Behaviour of Liquid Crystals
Authors: Kresse H.
Published: July 2007

The influence of the molecule structure on the dielectric anisotropy of nematic liquid crystals was experimentally investigated and discussed from the point of view of the Maier‐Meier theory. Further, the reorientation time of the dipoles in different smectic phases was measured and correlated to the structure of the phases. Some technical aspects are discussed in connection with the dielectric relaxation phenomenon.
Reliability critical thermal model for double‐drift IMPATT diodes on diamond heat sinks
Authors: Csanky G.
Published: July 2007

A thermal model of double‐drift IMPATT diodes on diamond heat sinks has been developed. The thermal model approximates the temperature‐dependent thermal conductivities of Si and diamond (Type II) by means of simple empirical formulae. The application of the thermal model to three IMPATT diode lots indicates that under life test, junction temperatures are greater than 700°C, and that the metal/Si interface temperatures exceed 500°C. An explanation of the failure mechanism is presented. Designs that result in a lower junction temperature are proposed.
System reliability prediction based on historical data
Authors: Usher John S. , Alexander Suraj M. , Thompson John D.
Published: July 2007

This paper describes the development and implementation of a computerized reliability prediction model at the IBM facility located in Research Triangle Park, North Carolina. Through the analysis of historical life‐test data, the model provides maximum likelihood estimates of the assumed Weibull life distributions of various types of components. The resulting component life distribution estimates are used to predict the reliability of new system configurations. This approach is based upon the well‐known theory of competing risks. Our model, however, is unique in that it allows for the analysis of a pooled set of life data, i.e. life data from different types of systems, to obtain component estimates. This feature greatly generalizes the competing risks framework and hence offers advantages over the more traditional approach. We present the model and discuss various issues that were found to be critical to its successful implementation at IBM.
Increasing importance of effects of marginal parts on reliability
Authors: Ganter William A.
Published: July 2007

In this paper, marginal parts are equated with low quality and low reliability. Marginal parts can be shown to cause errors in some products during tests. They are also a cause of field failures in these products. Although marginal parts causes still have a random failure time component, they have a much lower amount of variation than our traditional failure causes, hidden flaws. I give marginal parts a measurable definition. If marginal effects can be established for a product, then this knowledge can be used to improve reliability. Some examples of products where I believe this marginal effect holds are discussed in this paper. Such marginal effects on reliability are gaining more and more importance in systems that are increasing in complexity. A strong point in applying the marginal parts theory framed in this paper is that it can be readily subjected to statistical testing to see if it holds or not for any particular product.
Infant mortality modelling for vlsi devices using graphical estimation
Authors: Stoltze Paul L.
Published: July 2007

This paper presents a practical methodology for the routine analysis of VLSI infant mortality data. Device families are modelled using established graphical parameter estimation techniques, and the model parameters are applied to individual device types within the family. Burn‐in requirements are calculated to achieve a desired early life reliability level. A technical summary of the methods is presented, and a small data set is analysed as an example. The analysis results from three large device families are also presented.
Optoelectronics reliability
Authors: Ikegami Tetsuhiko , Fukuda Mitsuo
Published: July 2007

This paper reviews degradation modes and reliability in several kinds of InGaAsP/InP lasers and photodetectors used in optical fibre transmission systems. From the viewpoint of degradation mechanisms, BH type Fabry–Perot lasers, DFB lasers, a 0.98 μm strained quantum well InGaAs/GaAs laser, and InGaAs PIN photodetectors and APDs are reviewed.
Reliability improvement of electronic circuits based on physical failure mechanisms in components
Authors: Brombacher A. C. , de Boer H. A. , Bennion M. , Fennema P. H. , Herrmann O. E.
Published: July 2007

Traditionally the position of reliability analysis in the design and production process of electronic circuits is a position of reliability verification. A completed design is checked on reliability aspects and either rejected or accepted for production. This paper describes a method to model physical failure mechanisms within components in such a way that they can be used for reliability optimization, not after, but during the early phase of the design process. Furthermore a prototype of a CAD software tool is described, which can highlight components likely to fail and automatically adjust circuit parameters to improve product reliability.
Methods for the continuous assessment of reliability of specialized equipment
Authors: Watkins A. J. , Leech D. J.
Published: July 2007

This paper is concerned with the assessment of reliability for equipment which is highly specialized. Of particular interest is the analysis of field data early in the life of the fleet of such equipment. Factors affecting the data underlying assessments are outlined, and a basic statistical model for describing these data is introduced. Methods of assessment of equipment reliability, and the precision of such assessments, are discussed, examples of data from this basic model are analysed, and further examples illustrate the role of model parameters. The model may also be used to analyse incomplete data sets, and we consider the penalty incurred at different levels of incompleteness. The paper concludes with a discussion outlining further possible modifications and refinements to the basic model.
Measuring the quality of knowledge work
Authors: Coppola Anthony
Published: July 2007

There is a variety of ways to measure the quality of knowledge work. The best selection for a particular application depends on how the user defines quality and the intended use of the measure. This paper catalogues possible measures according to five different perspectives on quality and four different uses of quality measures. It concludes with some recommendations for measuring quality in a laboratory.