bluuebunny/crossref_metadata_2025 huggingface dataset:
Non‐working dental therapists: opportunities to ameliorate workforce shortages
Authors: Kruger E. , Smith K. , Tennant M.
Published: March 2008

Background: Workforce development is a critical factor allowing delivery on government health priorities. Against a backdrop of increasing demand for dental therapists being significantly higher than the levels of recruitment, it is widely acknowledged that rural and remote areas (having greater recruitment and retention issues) will face a significant shortfall in therapist numbers as the workforce shortages take hold in dentistry. This study analysed the reasons for dental therapists leaving the profession, and factors that would promote the recruitment and retention of dental therapists, especially in rural and remote areas.

Methods: A postal survey was undertaken amongst all registered dental therapists in Western Australia between the years 1999–2003.

Results: Of all respondents, 28 per cent indicated that they do not work as dental therapists anymore. A number of reasons for leaving the profession were highlighted, including family reasons, career change, poor salaries, relocation, illness and injury, and stress. To increase retention and recruitment of dental therapists to rural areas, a number of opportunities were highlighted by respondents, including increased salaries, living support, travel assistance, access to continuing education, recruitment of more rural students and more flexibility (including job sharing).

Conclusion: This survey has highlighted various opportunities to recruit and retain dental therapists in their profession and to increase the numbers of rural dental therapists. A broad integrated rural retention strategy is necessary to address these issues among the dental therapy workforce.
Evaluation of a combined thiourea and hydrogen peroxide regimen to bleach bloodstained teeth
Authors: Maiolo K. , Marin PD , Bridges TE , Heithersay GS
Published: March 2008

Background: Current techniques for intra‐coronal bleaching of stained root‐filled teeth employ oxidative bleaching with hydrogen peroxide. However, concern over the potential for invasive cervical resorption following the use of hydrogen peroxide has been expressed by many researchers, and recommendations have been made to limit the use of this agent. A reductive‐oxidative bleaching process using a thiourea and hydrogen peroxide regimen is proposed as an effective and safer bleaching combination. The efficacy of this novel bleaching regimen is evaluated in this study.

Methods: The study involved a quantitative and qualitative spectrophotometric assessment of the ability of two amine (bleaching) agents, aqueous thiourea and acidified thiourea, to alter the absorption spectra of haemoglobin and methaemoglobin compared to hydrogen peroxide. In addition, extracted premolar teeth discoloured by blood were subjected to different bleaching regimens using amine reducing agents and hydrogen peroxide. The change in the colour of the bloodstained dentine samples was measured at each stage of the bleaching process with a Photometer and Reflectance Densitometer. Comparisons of different treatments were made using a method of least significant difference and/or analysis of variance.

Results: Spectrophotometric studies showed that acidified thiourea solution greatly reduced the colour of the haemoglobin and methaemoglobin in the visible range (330–760nm). Aqueous thiourea had no effect on the presence of haemoglobin and methaemoglobin. Reflection Densitometer and Photometer scores indicate that the greatest bleaching effect was achieved by the combined acidified thiourea and hydrogen peroxide regimen.

Conclusion: The recognition that bleaching discoloured teeth is a chemical process, which can be achieved by both reducing and oxidizing agents, offers the possibility of developing new and safer clinical bleaching protocols. It is concluded that the bleaching regimen which employs the sequential use of 0.1M acidified thiourea and 30% w/v hydrogen peroxide is as effective at bleaching bloodstained dentine as 30% w/v hydrogen peroxide alone. However, the addition of thiourea to the bleaching regimen has the potential benefit of reducing the level of damaging hydroxyl radicals and achieving a safer bleaching process.
Factors influencing oral colonization of mutans streptococci in young children
Authors: Law V. , Seow WK , Townsend G.
Published: March 2008

This paper aims to critically review current knowledge about the key factors involved in oral colonization of the cariogenic group of bacteria, mutans streptococci (MS) in young children. MS, consisting mainly of the species Streptococcus mutans and Streptococcus sobrinus, are commonly cultured from the mouths of infants, with prevalence of infection ranging from around 30 per cent in 3 month old predentate children to over 80 per cent in 24 month old children with primary teeth. MS is usually transmitted to children through their mothers, and the risk of transmission increases with high maternal salivary levels of MS and frequent inoculation. Factors that affect the colonization of MS may be divided into bacterial virulence, host‐related and environmental factors. Complex interaction among these factors determine the success and timing of MS colonization in the child. As clinical studies have shown that caries risk is correlated with age at which initial MS colonization occurred, strategies for the prevention of dental caries should include timely control of colonization of the cariogenic bacteria in the mouths of young children.
Baby boomer retirement and the future of dentistry
Authors: Schofield DJ , Fletcher SL
Published: March 2008

Background: The dental workforce, like the Australian population, is ageing. As the large baby boomer cohort retires dental shortages will likely increase.

Methods: Australian Bureau of Statistics census data from 1986 to 2001 were used to examine ageing of the dental workforce and attrition of dentists aged 50 years and over. The number of dentists to retire was projected over the next 20 years.

Results: Since 1986, the dental workforce has aged significantly (p < 0.01). About half of the current dental workforce is projected to retire by 2026. Generation X dentists are significantly less likely to work long hours than the baby boomer cohort of dentists (p < 0.01). This is partly due to an increase in the proportion of women in the dental workforce and male Generation X dentists being less likely to work long hours (>41 per week) than male baby boomer dentists (p < 0.01).

Conclusions: Ageing of the workforce will have an impact on dentistry later than on some other professions due to the 35 per cent of dentists who work beyond 65 years of age. Nonetheless, existing dental shortages are likely to be exacerbated over the short term by the 22 per cent of dentists projected to retire over the next 10 years.
A new paradigm for operative dentistry
Authors: Mount GJ
Published: March 2008

It is over 100 years since GV Black gathered together most of the knowledge then current on the caries process and set clear parameters for the discipline of operative dentistry. His four‐volume treatise set standards that were relevant for the times and, in fact, were so well described that they remained dominant in this discipline until quite recently. However, over the last 50 years there has been great progress in scientific method and in knowledge of the common diseases of the oral environment, including the caries process, so maybe it is time for change.

The term “paradigm” describes a philosophy of science, a generally accepted model of how ideas relate to one another, forming a conceptual framework within which scientific research is carried out. Black defined the paradigm within which further research was to be conducted during the following years and the profession accepted his lead. However, it is not expected that the parameters of a profession should remain unchanged over a substantial period so it is suggested that the dental profession should, at this time, recognize a new paradigm.

Improvements in scientific method have led to a better understanding of the oral environment, resulting in extensive changes for this profession. It is suggested that the standards set by Black should be now consigned to history and an entirely new paradigm adopted. First, the profession must recognize that dental caries is a bacterial disease and its primary efforts should be directed towards identification and elimination of the disease prior to initiating repair of the damage that it has caused. Preservation of natural tooth structure is then the next responsibility. There should be maximum use made of preventive strategies, including remineralization, followed by minimal intervention cavity designs and the use of bioactive restorative materials to restore the lesions. The profession should be prepared to move on.
Profile of lingual orthodontic users in Australia
Authors: Chan EKM , McCrostie S. , Petocz P. , Darendeliler M Ali
Published: March 2008

Background: The use of lingual orthodontic appliances and the training background of orthodontists in Australia using the lingual orthodontic technique are largely unknown. The aim of this study was to investigate the profile of lingual orthodontic users in Australia.

Methods: Four hundred and fifty questionnaires consisting of 15 questions were sent out to orthodontists in Australia. We obtained a 62 per cent return rate (278) with a 58 per cent rate of completed questionnaires. Statistical analysis using SPSS was performed and various outputs were obtained.

Results: Of the completed returns, 23 per cent were current lingual users; 69 per cent were not and 8 per cent were previous users but have stopped using the appliance. The majority (90 per cent) of the current lingual users were males. The highest percentage of users (35 per cent) was in New South Wales while the smallest percentage was in Tasmania (2 per cent). Around 40 per cent of respondents attended lingual courses as part of their specialist training programme, while 73 per cent had attended lingual courses since graduation and 82 per cent would consider attending a lingual course in the future. Of the 60 per cent current users who did not have a lingual component in their specialist training programme, almost nine‐tenths had attended lingual courses since graduation. Of the non‐lingual users, 14 per cent attended lingual courses as part of their specialist training programme, 28 per cent attended lingual courses since graduation and 38 per cent would consider attending a lingual course in the future. The main reason cited for being a non‐lingual user was that lingual orthodontics could not be an integral part of the practice.

Conclusions: Most of the orthodontists who graduated more than 16 years ago from their postgraduate training were non‐users of the lingual appliance. It seems that around one in four orthodontists currently use the lingual technique, of which NSW orthodontists make up the largest group. Only one‐fifth of users had some lingual component in their formal orthodontic training and about half of them have attended lingual courses after graduation. Almost half of orthodontists in Australia would consider attending a lingual course in the future. This survey provides a sound basis for course co‐ordinators to plan for continuing lingual orthodontics in the future.
Clinical and pharmacological variables as a risk factor for nifedipine‐induced gingival overgrowth
Authors: Guncu GN , Caglayan F. , Dinçel A. , Bozkurt A. , Ozmen F. , Karabulut E.
Published: March 2008

Background: Gingival enlargement is usually noted within one to two months after the initiation of nifedipine therapy. The aetiology of nifedipine‐induced gingival overgrowth is uncertain. The aim of this study was to determine the relationship between plasma and gingival crevice fluid (GCF) nifedipine concentrations and the degree of gingival overgrowth in patients treated with nifedipine, and also to assess the correlations between clinical and pharmacological variables.

Methods: Eighteen patients taking nifedipine in regular doses for at least six months participated in the study. Gingival enlargement was evaluated with two indices to score vertical and horizontal overgrowth. Gingival index (GI), plaque index (PI), gingival bleeding time index (GBTI), probing depth (PD) and clinical attachment level (CAL) were also evaluated. GCF and plasma nifedipine concentrations were determined by using high performance liquid chromatography.

Results: There was no significant difference between responders and non‐responders for PI, GI and GBTI. The mean concentration of nifedipine in GCF was significantly greater than concentration in plasma. No significant difference was observed for GCF and plasma nifedipine concentration between responders and non‐responders.

Conclusions: The present study showed that neither GCF nor plasma nifedipine levels appeared to be a risk factor for nifedipine‐induced gingival overgrowth. Improving the oral hygiene in patients using nifedipine may help control the degree of drug‐induced gingival enlargement.
The differential diagnosis of toothache from other orofacial pains in clinical practice
Authors: Linn J. , Trantor I. , Teo N. , Thanigaivel R. , Goss AN
Published: March 2008

Background: Teeth are a common and obvious source of orofacial pain. There is a risk that endodontic treatment may be initiated in patients that do not have pulp or periapical pathosis.

Methods: A retrospective survey of a sample of patients referred for endodontic treatment was analysed to determine the accuracy of the diagnosis and to identify non‐dental cases. A separate prospective study of complex non‐dental orofacial pain cases was performed to determine which cases had previously received dental treatment.

Results: Seventy‐seven (88 per cent) of 88 patients referred for endodontic treatment had been correctly diagnosed with solely endodontic problems. Eight (9 per cent) had endodontic plus other orofacial pain problems and three (3 per cent) had no endodontic problems but other orofacial pain problems. Forty‐four (44 per cent) of 100 non‐dental orofacial pain patients had previously received either extractions or endodontics.

Conclusion: Dentists need to carefully evaluate all toothache patients to ensure that the diagnosis is correct prior to the initiation of irreversible treatment.
A clinical classification of the status of the pulp and the root canal system
Authors: Abbott PV , Yu C.
Published: March 2008

Many different classification systems have been advocated for pulp diseases. However, most of them are based on histopathological findings rather than clinical findings which leads to confusion since there is little correlation between them. Most classifications mix clinical and histological terms resulting in misleading terminology and diagnoses. This in turn leads to further confusion and uncertainty in clinical practice when a rational treatment plan needs to be established in order to manage a specific pathological entity. A simple, yet practical classification of pulp diseases which uses terminology related to clinical findings is proposed. This classification will help clinicians understand the progressive nature of the pulp disease processes and direct them to the most appropriate and conservative treatment strategy for each condition. With a comprehensive knowledge of the pathophysiology of pain and inflammation in the pulp tissues, clinicians may accomplish this task with confidence.
The use of calcium hydroxide, antibiotics and biocides as antimicrobial medicaments in endodontics
Authors: Athanassiadis B. , Abbott PV , Walsh LJ
Published: March 2008

Bacteria have been implicated in the pathogenesis and progression of pulp and periapical diseases. The primary aim of endodontic treatment is to remove as many bacteria as possible from the root canal system and then to create an environment in which any remaining organisms cannot survive. This can only be achieved through the use of a combination of aseptic treatment techniques, chemomechanical preparation of the root canal, antimicrobial irrigating solutions and intracanal medicaments. The choice of which intracanal medicament to use is dependent on having an accurate diagnosis of the condition being treated, as well as a thorough knowledge of the type of organisms likely to be involved and their mechanisms of growth and survival. Since the disease is likely to have been caused by the presence of bacteria within the root canal, the use of an antimicrobial agent is essential. Many medicaments have been used in an attempt to achieve the above aims but no single preparation has been found to be completely predictable or effective. Commonly used medicaments include calcium hydroxide, antibiotics, non‐phenolic biocides, phenolic biocides and iodine compounds. Each has advantages and disadvantages, and further research is required to determine which is best suited for root canal infections.
Frost protection of buried PVC water mains in western Canada
Authors: Sepehr K. , Goodrich L.E.
Published: March 2008

Although desirable for many reasons, controlled low-strength material – controlled density fill (nonshrinkable fill) has the potential to promote rapid frost penetration within the trench when used as a backfill material in waterworks construction and repair projects. This paper describes results of a two-dimensional finite-element heat-transfer model study carried out to investigate the effectiveness of various insulation systems for frost and frost-heave protection of buried waterlines. Combinations of nonshrinkable fill with horizontal insulation boards, cylindrical pipe insulation, and inverted U-shaped insulations were investigated. It was shown that, while moderate thicknesses of insulation could be found to protect the pipe from freezing, thermal-bridging effects make the location of the maximum frost penetration depth sensitive to details of the insulation geometry. The use of different combinations of insulating backfills was also investigated, and it was shown that a backfill layer of moderate insulating value placed high in the trench may be most advantageous. Key words : frost, frost protection, insulation, waterlines, nonshrinkable fill, numerical analysis.
Behaviour of flexible piles in layered sands under eccentric and inclined loads
Authors: Sastry V.V.R.N. , Meyerhof G.G.
Published: March 2008

The lateral soil pressures, bending moments, pile displacements at ground surface, and bearing capacity of instrumented vertical single flexible model piles in layered sands consisting of loose sand overlying compact sand under vertical eccentric and central inclined loads have been investigated. The results of these load tests are compared with theoretical estimates based on the concept of an effective embedment depth of equivalent rigid piles. Reasonable agreement has been found between the observed and predicted behaviour of flexible piles. The analyses are also compared with the results of some field case records. Key words : bearing capacity, instrumentation, model test, layered soil, pile, sand.
Field observations on the load–strain–time behaviour of geogrid reinforcement
Authors: Fannin R.J.
Published: March 2008

Field data are reported that describe the load–strain–time relationship of geogrid reinforcement in a reinforced soil structure. The data are for a period exceeding 5 years and reveal a continued strain in the reinforcement, which occurs at nearly constant load. The response to loading is attributed to creep of the polymeric material. A comparison of the field data with laboratory isochronous load–strain curves, from rapid loading creep tests performed at a temperature similar to the mean annual temperature in the backfill soil, shows the curves describe very well the magnitude of creep strains observed in the field. Implications of the load–strain–time performance data are assessed with reference to the use in design of a tensile strength established from the rapid-loading creep test and wide-width strip test. The need to clarify, in design of polymeric reinforced soil structures, between a safe and allowable tensile strength is emphasized. Key words : reinforced soil, geogrid, creep, tensile strength, strain.
Centrifuge techniques for testing clay liner samples
Authors: Mitchell R.J.
Published: March 2008

The evaluation of clay liner – permeant compatibility is an area of current research interest because of concerns for environmental protection. It is also an area of some concern with regard to test methodology, due to adverse effects of using either a rigid-walled or a flexible-walled test cell. This, paper describes the development and use of a "flexible, no lateral strain" centrifuge test cell, designed to evaluate clay liner-permeant compatibility under prototype effective-stress conditions. Some preliminary test results are presented. Key words : clay liners, permeability, leachate compatibility, no lateral strain.
Dynamic response of single piles and soilpile interaction
Authors: Dou Huaren , Byrne Peter M
Published: March 2008

Pile reponse to earthquake loading and soilpile interaction behaviour were investigated experimentally using the hydraulic gradient similitude technique. The unique feature of this method is the application of a very high hydraulic gradient to increase the effective stresses in the model, simulating full-scale stress conditions in the field. The dynamic loading was applied to model piles using a conventional shake table. Tests on model piles embedded in dense sands are described herein. Both free vibration and forced vibration simulating earthquake loading were carried out. Pile bending moment, deflection, and acceleration were measured during testing. Dynamic py curves were derived from the measurements and were found to be highly nonlinear and hysteretic at shallow depths under strong shaking. The py curves for low-level shaking showed essentially linear elastic behaviour. The experimental py curves were compared with the backbone py curves for sand recommended by the American Petroleum Institute, and the agreement was reasonable except at shallow depths.

Key words: pile, hydraulic gradient, modelling, vibration, shaking, py curve.
In situ tests in Brasília porous clay
Authors: Ortigao J A.R , Cunha R P , Alves L S
Published: March 2008

An in situ testing programme was carried out in 1992 aimed at obtaining design parameters for the construction of the Brasília Underground line, Brazil. The top layer of soil consisted of an unsaturated and collapsible soft porous clay layer 530 m thick followed by residual soils from slate and interlayered metasiltsones and quartzites. A series of Marchetti dilatometer (DMT) logging tests results were comapred with Ménard pressuremeter (PMT) and horizontal plate loading (PLH) tests, as well as laboratory tests on block samples. In situ stresses, strength, and deformation parameters were obtained for the porous clay. The DMT yielded very good results: excellent repeatability, low cost, and results that agree with other in situ tests and laboratory data.

Key words: porous clay, in situ testing, dilatometer, pressuremeter.
CONSTRAINTS ON LARGE-SCALE MAGNETIC FIELDS FROM THE AUGER RESULTS
Authors: DE ANGELIS ALESSANDRO , PERSIC MASSIMO , RONCADELLI MARCO
Published: March 2008

A recent article from the Pierre Auger Collaboration links the direction of charged cosmic rays to possible extragalactic sites of emission. The correlation of the direction of such particles with the direction of the emitter allows constraining the value of large-scale magnetic fields B. Assuming for B a coherence length λ in the range between 1 Mpc and 10 Mpc, we find values of B between 0.3 and 0.9 nG.
THE FLUCTUATION SPECTRA AROUND A GAUSSIAN CLASSICAL SOLUTION OF A TENSOR MODEL AND THE GENERAL RELATIVITY
Authors: SASAKURA NAOKI
Published: March 2008

Tensor models can be interpreted as theory of dynamical fuzzy spaces. In this paper, I study numerically the fluctuation spectra around a Gaussian classical solution of a tensor model, which represents a fuzzy flat space in arbitrary dimensions. It is found that the momentum distribution of the low-lying low-momentum spectra is in agreement with that of the metric tensor modulo the general coordinate transformation in the general relativity at least in the dimensions studied numerically, i.e. one to four dimensions. This result suggests that the effective field theory around the solution is described in a similar manner as the general relativity.
NUMERICAL SIMULATION OF FLOW FEATURES AND ENERGY EXCHANGE PHYSICS IN NEAR-WALL REGION WITH FLUID-STRUCTURE INTERACTION
Authors: ZHANG LIXIANG , WANG WENQUAN , GUO YAKUN
Published: March 2008

Large eddy simulation is used to explore flow features and energy exchange physics between turbulent flow and structure vibration in the near-wall region with fluid–structure interaction (FSI). The statistical turbulence characteristics in the near-wall region of a vibrating wall, such as the skin frictional coefficient, velocity, pressure, vortices, and the coherent structures have been studied for an aerofoil blade passage of a true three-dimensional hydroturbine. The results show that (i) FSI greatly strengthens the turbulence in the inner region of y+ < 25; and (ii) the energy exchange mechanism between the flow and the vibration depends strongly on the vibration-induced vorticity in the inner region. The structural vibration provokes a frequent action between the low- and high-speed streaks to balance the energy deficit caused by the vibration. The velocity profile in the inner layer near the vibrating wall has a significant distinctness, and the viscosity effect of the fluid in the inner region decreases due to the vibration. The flow features in the inner layer are altered by a suitable wall vibration.
VERTEX FUNCTIONS FOR THE DESCRIPTION OF HETEROPHASE STATES IN THE LANDAU THEORY OF PHASE TRANSITIONS IN POLYDISPERSE COPOLYMERS
Authors: KUCHANOV S. I. , ALIEV M. A.
Published: March 2008

The diagram technique suggested earlier to find vertex functions for the description of homophase states in the framework of the Landau theory of phase transitions in polydisperse copolymers is extended to the description of heterophase states.
DYNAMICS OF PERTURBATIONS IN GURZADYAN–XUE COSMOLOGICAL MODELS
Authors: VERESHCHAGIN G. V. , YEGORIAN G.
Published: March 2008

Perturbation theory within Newtonian approximation is presented for cosmological models with time-varying physical constants. Analytical solutions for perturbations dynamics are obtained for each Gurzadyan–Xue model with pressureless matter and radiation. It is found that perturbations grow during the entire expansion within GX models, including the curvature- and vacuum-dominated stage when they cease to grow in the standard cosmological model.
FRIEDMANN EQUATION FOR BRANS–DICKE COSMOLOGY
Authors: ARIK M. , ÇALIK M. , SHEFTEL M. B.
Published: March 2008

In the context of the Brans–Dicke scalar tensor theory of gravitation, the cosmological Friedmann equation which relates the expansion rate H of the universe to the various fractions of energy density is analyzed rigorously. It is shown that the Brans–Dicke scalar tensor theory of gravitation brings a negligible correction to the matter density component of the Friedmann equation. Besides, in addition to ΩΛ and ΩM in the standard Einstein cosmology, another density parameter, ΩΔ, is expected by the theory inevitably. Some cosmological consequences of such nonfamiliar cases are examined as far as recent observational results are concerned. Theory implies that if ΩΔ is found to be nonzero, data can favor this model and hence this theory turns out to be the most powerful candidate in place of the standard Einstein cosmological model with cosmological constant. Such a replacement will enable more accurate predictions for the rate of change of the Newtonian gravitational constant in the future.
EXACT SOLUTIONS OF EMBEDDING THE 4D UNIVERSE IN A 5D EINSTEIN MANIFOLD
Authors: MENG XIN-HE , REN JIE , ZHANG HONG-GUANG
Published: March 2008

One of the simplest ways to extend 4D cosmological models is to add another spatial dimension to make them 5D. In particular, it has been shown that the simplest of such 5D models, i.e. one in which the right-hand side of the Einstein equation is empty, induces a 4D nonempty universe. Accordingly, the origin of matter in a real 4D universe might be mathematically attributed to the existence of one (fictitious) extra spatial dimension. Here we consider the case of an empty 5D universe possessing a cosmological constant Λ and obtain exact solutions for both positive and negative values of the Λ. It is seen that such a model can naturally reduce to a power law ΛCDM model for the real universe. Further, it can be seen that the arbitrary constants and functions appearing in this model are endowed with definite physical meanings.
ACCELERATION OF THE UNIVERSE DRIVEN BY THE CASIMIR FORCE
Authors: SZYDŁOWSKI MAREK , GODŁOWSKI WŁODZIMIERZ
Published: March 2008

We investigate an evolutional scenario of the FRW universe with the Casimir energy scaling like (-)(1 + z)4. The Casimir effect is used to explain the vacuum energy differences (its value measured in astrophysics is very small compared to the value obtained from quantum-field-theory calculations). The dynamics of the FRW model is represented in terms of a two-dimensional dynamical system to show all evolutional paths of this model in the phase space for all admissible initial conditions. We find also an exact solution for nonflat evolutional paths of the Universe driven by the Casimir effect. The main difference between the FRW model with the Casimir force and the ΛCDM model is that their generic solutions are a set of evolutional paths with a bounce solution and an initial singularity, respectively. The evolutional scenario is tested by using the SNIa data, FRIIb radiogalaxies, baryon oscillation peak and CMB observation. We compare the power of explanation of the model considered and the ΛCDM model using the Bayesian information criterion and the Bayesian factor. Our investigation of the information criteria of model selection showed preference for the ΛCDM model over other models considered. However, the presence of the negative-like radiation term can remove a tension between the theoretical and the observed primordial4He and D abundance.
COMPLEXITY OF A DELAYED PREDATOR–PREY MODEL WITH IMPULSIVE HARVEST AND HOLLING TYPE II FUNCTIONAL RESPONSE
Authors: ZENG GUANGZHAO , WANG FENGYAN , NIETO JUAN J.
Published: March 2008

We study an impulsive delay differential predator–prey model with Holling type II functional response. The stability of the trivial equilibrium is analyzed by means of impulsive Floquet theory providing a sufficient condition for extinction. Using coincidence degree theory we show the existence of positive periodic solutions. The system is then analyzed numerically, revealing that the presence of delays and impulses may lead to chaotic solutions, quasi-periodic solutions, or multiple periodic solutions. Several simulations and examples are presented.
MiniMesh
Authors: Chin Kwan-Wu , Lowe Darryn
Published: March 2008

This paper proposes MiniMesh, an opportunistic transmission mechanism for the IEEE 802.15.3 medium access control (MAC) protocol; a key technology to realizing wireless personal area networks (WPANs). MiniMesh exploits the varying channel conditions to devices in a WPAN, thereby enabling the sender and receiver of a flow to transmit at high data rates when the channel condition is favorable. In addition, MiniMesh addresses the coverage problem that limits peer-to-peer communications and is backward compatible with the IEEE 802.15.3 specification. We have implemented MiniMesh and the DS-UWB physical layer that offers data rates ranging from 28 Mbps to 1 Gbps in the
ns-2
simulator. Our results show devices obtain at least a three fold increase in throughput when only the piconet controller is serving as a relay; further increases are possible with additional relays. Moreover, a flow experiences faster recovery from packet loss and is able to maintain a high throughput even when channel conditions worsen.
SIGMOBILE FY'07 annual report
Authors: Johnson David B.
Published: March 2008

This article reproduces SIGMOBILE's Annual Report to ACM for the period July 1, 2006, through June 30, 2007. Corresponding to ACM's fiscal year cycle, each SIG Chair is required to submit an annual report to ACM's SIG Governing Board that summarizes the highlights of the SIG's activities over the previous year. This has been another great year for SIGMOBILE; we hope you were able to share it with us and hope you will join us for many more in the years to come.
Guest editors' introduction
Authors: Stojanovic Milica , Fall Kevin
Published: March 2008

Wireless information transmission underwater is one of the enabling technologies for the development of future ocean-observation systems, whose applications include gathering of scientific data, pollution control, climate monitoring, detection of objects on the ocean floor, and transmission of images from remote sites. Implicitly, wireless signal transmission is crucial for control of autonomous underwater vehicles (AUVs) which will serve as mobile nodes in the future information networks of distributed underwater sensors. Wireless communication provides advantages of collecting data without the need to retrieve instruments, and maneuvering underwater vehicles and robots without the burden of cables. It is most often accomplished using acoustic transmission, although other approaches including optics and electromagnetic fields are also being investigated for short-range high-bandwidth links.
On the relationship between capacity and distance in an underwater acoustic communication channel
Authors: Stojanovic Milica
Published: March 2008

Path loss of an underwater acoustic communication channel depends not only on the transmission distance, but also on the signal frequency. As a result, the useful bandwidth depends on the transmission distance, a feature that distinguishes an underwater acoustic system from a terrestrial radio one. This fact influences the design of an acoustic network: a greater information throughput is available if messages are relayed over multiple short hops instead of being transmitted directly over one long hop. We asses the bandwidth dependency on the distance using an analytical method that takes into account physical models of acoustic propagation loss and ambient noise. A simple, single-path time-invariant model is considered as a first step. To assess the fundamental bandwidth limitation, we take an information-theoretic approach and define the bandwidth corresponding to optimal signal energy allocation -- one that maximizes the channel capacity subject to the constraint that the transmission power is finite. Numerical evaluation quantifies the bandwidth and the channel capacity, as well as the transmission power needed to achieve a pre-specified SNR threshold, as functions of distance. These results lead to closed-form approximations, which may become useful tools in the design and analysis of acoustic networks.
Meet the Virts
Authors: Killalea Tom
Published: March 2008

When you dig into the details of supposedly overnight success stories, you frequently discover that they’ve actually been years in the making. Virtualization has been around for more than 30 years since the days when some of you were feeding stacks of punch cards into very physical machines yet in 2007 it tipped. VMware was the IPO sensation of the year; in November 2007 no fewer than four major operating system vendors (Microsoft, Oracle, Red Hat, and Sun) announced significant new virtualization capabilities; and among fashionable technologists it seems virtual has become the new black.
The Cost of Virtualization
Authors: Drepper Ulrich
Published: March 2008

Virtualization can be implemented in many different ways. It can be done with and without hardware support. The virtualized operating system can be expected to be changed in preparation for virtualization, or it can be expected to work unchanged. Regardless, software developers must strive to meet the three goals of virtualization spelled out by Gerald Popek and Robert Goldberg: fidelity, performance, and safety.
How OSGi Changed My Life
Authors: Kriens Peter
Published: March 2008

In the early 1980s I discovered OOP (object-oriented programming) and fell in love with it, head over heels. As usual, this kind of love meant convincing management to invest in this new technology, and most important of all, send me to cool conferences. So I pitched the technology to my manager. I sketched him the rosy future, how one day we would create applications from ready-made classes. We would get those classes from a repository, put them together, and voila, a new application would be born. Today we take objects more or less for granted, but if I am honest, the pitch I gave to my manager in 1985 never really materialized. The reuse of objects never achieved the levels foreseen by people such as Brad Cox with his software-IC model, and many others, including myself. Still, this Lego hypothesis remains a grail worth pursuing.
All Things Being Equal?
Authors: Kelly-Bootle Stan
Published: March 2008

By the time these belles-lettres reach you, a brand new year will be upon us. Another Year! Another Mighty Blow! as Tennyson thundered. Or as Humphrey Lyttelton (q.g.) might say, "The odious odometer of Time has clicked up another ratchette of entropic torture." Less fancifully, as well as trying hard not to write 2007 on our checks, many of us will take the opportunity to reflect on all the daft things we did last year and resolve not to do them no more. Not to mention all the nice things we failed to do. I have in mind the times when I missed an essential semicolon, balanced by the occasions when inserting a spurious one was equally calamitous. Surely any half-decent computer language should know where my statements are meant to terminate, and then properly redistribute the punctuation provided? The smarter Lisps became good at DWIM (do what I mean), balancing those damned, spurious parentheses. But I digress, having planted a topic known to incite reader feedback.
Acute and chronic ethanol consumption differentially impact pathways limiting hepatic protein synthesis
Authors: Karinch Anne M. , Martin Jonathan H. , Vary Thomas C.
Published: March 2008

This review identifies the various pathways responsible for modulating hepatic protein synthesis following acute and chronic alcohol intoxication and describes the mechanism(s) responsible for these changes. Alcohol intoxication induces a defect in global protein synthetic rates that is localized to impaired translation of mRNA at the level of peptide-chain initiation. Translation initiation is regulated at two steps: formation of the 43S preinitiation complex [controlled by eukaryotic initiation factors 2 (eIF2) and 2B (eIF2B)] and the binding of mRNA to the 40S ribosome (controlled by the eIF4F complex). To date, alcohol-induced alterations in eIF2 and eIF2B content and activity are best investigated. Ethanol decreases eIF2B activity when ingested either acutely or chronically. The reduced eIF2B activity most likely is a consequence of twofold increased phosphorylation of the α-subunit of eIF2 on Ser51following acute intoxication. The increase in eIF2α phosphorylation after chronic alcohol consumption is the same as that induced by acute ethanol intoxication, and protein synthesis is not further reduced by long-term alcohol ingestion despite additional reduced expression of initiation factors and elongation factors. eIF2α phosphorylation alone appears sufficient to maximally inhibit hepatic protein synthesis. Indeed, pretreatment with Salubrinal, an inhibitor of eIF2α(P) phosphatase, before ethanol treatment does not further inhibit protein synthesis or increase eIF2α phosphorylation, suggesting that acute ethanol intoxication causes maximal eIF2α phosphorylation elevation and hepatic protein synthesis inhibition. Ethanol-induced inhibition of hepatic protein synthesis is not rapidly reversed by cessation of ethanol consumption. In conclusion, sustained eIF2α phosphorylation is a hallmark of excessive alcohol intake leading to inhibition of protein synthesis. Enhanced phosphorylation of eIF2α represents a unique response of liver to alcohol intoxication, because the ethanol-induced elevation of eIF2α(P) is not observed in skeletal muscle or heart.
Restraint increases afebrile body temperature but attenuates fever in Pekin ducks (Anas platyrhynchos)
Authors: Gray David A. , Maloney Shane K. , Kamerman Peter R.
Published: March 2008

In mammals, procedures such as handling, restraint, or exposure to open spaces induces an increase in body temperature (Tb). The increase in temperature shares some characteristics with pyrogen-induced fever and so is often called “stress fever.” Birds also respond to acute handling with a stress fever, which may confound thermoregulatory studies that involve animal restraint. We have measured the Tb responses of Pekin ducks on days when they were restrained and compared them to days when the birds remained unrestrained. Restraint induced a 0.5°C increase in Tb that was sustained for the entire 8 h of restraint. To determine whether the restraint-induced increase in Tb is mediated by prostaglandins (PGs) we compared the Tb responses during restraint after intraperitoneal injection with saline to the responses during restraint after injection with diclofenac sodium (15 mg/kg). There was no difference in response, suggesting that restraint affects Tb by a PG-independent mechanism. We also compared the Tb response to intramuscular injection of lipopolysaccharide (LPS; 100 μg/kg), a bacterial pyrogen, when the ducks were restrained or unrestrained. Despite Tb being higher at the time of LPS injection when the ducks were restrained, the maximum temperature reached after LPS injection was higher, and the period that Tb remained elevated was longer when the ducks were unrestrained. We conclude that restraint should be considered as a potential confounder in thermoregulatory studies in birds and presumably other species too.
Identification and subcellular localization of a new cystinosin isoform
Authors: Taranta Anna , Petrini Stefania , Palma Alessia , Mannucci Liliana , Wilmer Martijn J. , De Luca Veronica , Diomedi-Camassei Francesca , Corallini Serena , Bellomo Francesco , van den Heuvel Lambert P. , Levtchenko Elena N. , Emma Francesco
Published: March 2008

Nephropathic cystinosis is a lysosomal disorder caused by functional defects of cystinosin, which mediates cystine efflux into the cytosol. The protein sequence contains at least two signals that target the protein to the lysosomal compartment, one of which is located at the carboxy terminal tail (GYDQL). We have isolated from a human kidney cDNA library a cystinosin isoform, which is generated by an alternative splicing of exon 12 that removes the GYDQL motif. Based on its last three amino acids, we have termed this protein cystinosin-LKG. Contrary to the lysosomal cystinosin isoform, expression experiments performed by transient transfection of green fluorescent protein fusion plasmids in HK2 cells showed that cystinosin-LKG is expressed in the plasma membrane, in lysosomes, and in other cytosolic structures. This subcellular localization of the protein was confirmed by transmission electron microscopy. In addition, immunogold labeling was observed in the endoplasmic reticulum and in the Golgi apparatus. Expression of the protein in renal tubular structures was also directly demonstrated by immunostaining of normal human kidney sections. The plasma membrane localization of cystinosin-LKG was directly tested by [35S]cystine flux experiments in COS-1 cells. In the presence of a proton gradient, a marked enhancement of intracellular cystine transport was observed in cells overexpressing this isoform. These data indicate that the expression of the gene products encoded by the CTNS gene is not restricted to the lysosomal compartment. These finding may help elucidate the mechanisms of cell dysfunction in this disorder.
Spatiotemporally Graded NMDA Spike/Plateau Potentials in Basal Dendrites of Neocortical Pyramidal Neurons
Authors: Major Guy , Polsky Alon , Denk Winfried , Schiller Jackie , Tank David W.
Published: March 2008

Glutamatergic inputs clustered over ∼20–40 μm can elicit local N-methyl-d-aspartate (NMDA) spike/plateau potentials in terminal dendrites of cortical pyramidal neurons, inspiring the notion that a single terminal dendrite can function as a decision-making computational subunit. A typical terminal basal dendrite is ∼100–200 μm long: could it function as multiple decision-making subunits? We test this by sequential focal stimulation of multiple sites along terminal basal dendrites of layer 5 pyramidal neurons in rat somatosensory cortical brain slices, using iontophoresis or uncaging of brief glutamate pulses. There was an approximately sevenfold spatial gradient in average spike/plateau amplitude measured at the soma, from ∼3 mV for distal inputs to ∼23 mV for proximal inputs. Spike/plateaus were NMDA receptor (NMDAR) conductance-dominated at all locations. Large Ca2+ transients accompanied spike/plateaus over a ∼10- to 40-μm zone around the input site; smaller Ca2+ transients extended approximately uniformly to the dendritic tip. Spike/plateau duration grew with increasing glutamate and depolarization; high Ca2+ zone size grew with spike/plateau duration. The minimum high Ca2+ zone half-width (just above NMDA spike threshold) increased from distal (∼10 μm) to proximal locations (∼25 μm), as did the NMDA spike glutamate threshold. Depolarization reduced glutamate thresholds. Simulations exploring multi-site interactions based on this demonstrate that if appropriately timed and localized inputs occur in vivo, a single basal dendrite could correspond to a cascade of multiple co-operating dynamic decision-making subunits able to retain information for hundreds of milliseconds, with increasing influence on neural output from distal to proximal. Dendritic NMDA spike/plateaus are thus well-suited to support graded persistent firing.
Mitogen-Activated Protein Kinase Kinase 4/c-Jun NH2-Terminal Kinase Kinase 1 Protein Expression Is Subject to Translational Regulation in Prostate Cancer Cell Lines
Authors: Robinson Victoria L. , Shalhav Ore , Otto Kristen , Kawai Tomoko , Gorospe Myriam , Rinker-Schaeffer Carrie W.
Published: March 2008

Mitogen-activated protein kinase kinase 4/c-Jun NH2-terminal kinase kinase 1 (MKK4/JNKK1; hereafter referred to as MKK4) is a dual-specificity kinase with a critical role in regulating the activity of c-Jun NH2-terminal kinase and p38 kinases. We identified a novel biological function for MKK4 in the regulation of growth of ovarian and prostate cancer metastases. Clinical correlative studies showed that MKK4 protein levels were reduced in high-grade prostate cancer and prostate and ovarian cancer metastases compared with normal tissue, which prompted investigation into the mechanism(s) responsible for down-regulation of MKK4 in a panel of cancer cell lines. Initial studies found that low levels of MKK4 protein did not correlate with either exon deletion or decreased levels of MKK4 mRNA, suggesting that MKK4 protein levels were regulated posttranscriptionally by either reduced translation or reduced protein stability. Endogenous MKK4 was highly stable and not subject to altered proteolysis. Instead, MKK4 biosynthesis seemed to be regulated by altered translation. In support of this assertion, we found that cytosolic MKK4 mRNA was shifted toward active polysomes in cells with higher levels of MKK4 protein, suggesting that MKK4 mRNA was translated more efficiently in these cells. This study supports a novel mechanism for the regulation of MKK4 protein levels. Further, these findings have potential therapeutic implications for modulating the expression of a signaling kinase involved in the regulation of metastatic growth. (Mol Cancer Res 2008;6(3):501–8)