Showing papers by "Nova Southeastern University published in 2006"

Effects of staining and bleaching on color change of dental composite resins

Abstract: Statement of problem Discoloration of resin-based composites by colored solutions is a common problem. The use of bleaching agents for discolored natural teeth is becoming increasingly popular. It is not clear if bleaching agents can remove the stain from composite resins. Purpose The purpose of this study was to investigate the effects of 2 staining solutions and 3 bleaching systems on the color changes of 2 dental composite resins. Material and methods Forty-five disk-shaped specimens (9 × 2.5 mm) of each of 2 composite resins, Filtek Supreme (FS) and Esthet X (EX), were prepared. The specimens were then divided into 3 groups of 15 specimens each and immersed in 2 staining solutions (coffee or red wine) or distilled water (control) for 3 hours daily over a 40-day test period. The 3 groups were then divided into 3 subgroups (n=5), and 3 bleaching agents (Crest Night Effects, Colgate Simply White Night, or Opalescence Quick) were applied to the surface of the specimens over a 14-day period. Color of the specimens was measured with a spectrophotometer using CIELAB color space relative to CIE standard illuminant D55 at baseline, after staining, and after bleaching. The color differences (ΔE ab ∗ ) between the 3 measurements were calculated. The value ΔE ab ∗ =3.3 was used as an acceptable value in subjective visual evaluations. Analysis of variance and nonparametric analysis (Kruskal-Wallis test and Mann-Whitney test) were used to analyze the data. Results After staining, FS had more color change than EX and was more affected by the wine solution. After bleaching, the color of both EX and FS specimens returned to the baseline. The color differences between bleaching and baseline were less than value ΔE ab ∗ =3.3 for all groups. Conclusion The nanocomposite (FS) changed color more than the microhybrid composite (EX) as a result of staining in coffee or red wine solutions. After bleaching, discoloration was removed completely from the composite resins tested.

Bisphosphonate-associated osteonecrosis: a long-term complication of bisphosphonate treatment

Abstract: We present current knowledge of bisphosphonate-associated osteonecrosis, a new oral complication in oncology. It was first described in 2003, and hundreds of cases have been reported worldwide. The disorder affects patients with cancer on bisphosphonate treatment for multiple myeloma or bone metastasis from breast, prostate, or lung cancer. Bisphosphonate-associated osteonecrosis is characterised by the unexpected appearance of necrotic bone in the oral cavity. Osteonecrosis can develop spontaneously or after an invasive surgical procedure such as dental extraction. Patients might have severe pain or be asymptomatic. Symptoms can mimic routine dental problems such as decay or periodontal disease. Intravenous use of pamidronate and zoledronic acid is associated with most cases. Other risk factors include duration of bisphosphonate treatment (ie, 36 months and longer), old age in patients with multiple myeloma, and a history of recent dental extraction. We also discuss pathobiology, clinical features, management, and future directions for the disorder.

Battered woman syndrome: empirical findings.

Abstract: The construct of Battered Woman Syndrome (BWS) has been conceptualized as a subcategory of posttraumatic stress disorder (PTSD). It is composed of the following symptoms: (a) re-experiencing the battering as if it were reoccurring even when it is not, (b) attempts to avoid the psychological impact of battering by avoiding activities, people, and emotions, (c) hyperarousal or hypervigilance, (d) disrupted interpersonal relationships, (e) body image distortion or other somatic concerns, and (f) sexuality and intimacy issues. This article presents empirical data derived from administering the Battered Woman Syndrome Questionnaire (BWSQ) to women of four countries--United States, Spain, Greece, and Russia. The data support a theory of BWS.

Clinical and demographic predictors of long-term disability in patients with relapsing-remitting multiple sclerosis: a systematic review.

Abstract: Objective To identify clinical and demographic factors associated with long-term disability in patients with relapsing-remitting multiple sclerosis. Data sources We searched the MEDLINE (1966-May 2005), EMBASE, CINAHL, Cochrane, and PsycINFO computerized databases, and reviewed reference lists of retrieved articles. Study selection We included studies that examined predictors of long-term disability in patients with relapsing-remitting multiple sclerosis. We excluded studies that did not distinguish relapsing-remitting multiple sclerosis from primary progressive multiple sclerosis, enrolled fewer than 40 subjects, observed subjects for less than 5 years, or collected follow-up information in less than 80% of the inception cohort. Data extraction Two reviewers assessed study quality in 4 domains: cohort assembly, definitions and assessments of prognostic factors and outcomes, and statistical methods. One reviewer extracted data on the direction, magnitude, precision, and statistical significance of the effect of each predictor on prognosis. Data synthesis Heterogeneity of study designs precluded us from pooling the results of 27 eligible studies. Study quality was limited by cross-sectional design, enrollment of prevalent cases from referral centers, and lack of multivariate adjustment. Sphincter symptoms at onset (hazard ratio, 1.1-3.1), incomplete recovery from the first attack (hazard ratio, 1.3-3.3), and a short interval between the first and second attack (hazard ratio, 1.6-1.9) were most strongly and consistently associated with poor prognosis. Other factors widely believed to be of prognostic importance, including sex and age at onset, demonstrated inconsistent or weak effects on prognosis. Conclusions The most robust predictors of long-term physical disability in relapsing-remitting multiple sclerosis are sphincter symptoms at onset and early disease course outcomes. These factors can be used to guide treatment decisions for drugs with significant toxicities.

On Similarity Indices and Correction for Chance Agreement

Abstract: Similarity indices can be used to compare partitions (clusterings) of a data set. Many such indices were introduced in the literature over the years. We are showing that out of 28 indices we were able to track, there are 22 different ones. Even though their values differ for the same clusterings compared, after correcting for agreement attributed to chance only, their values become similar and some of them even become equivalent. Consequently, the problem of choice of the index to be used for comparing different clusterings becomes less important.

An overview of the higher level classification of Pucciniomycotina based on combined analyses of nuclear large and small subunit rDNA sequences

Abstract: In this study we provide a phylogenetically based introduction to the classes and orders of Pucciniomycotina (5Urediniomycetes), one of three subphyla of Basidiomycota. More than 8000 species of Pucciniomycotina have been described including putative saprotrophs and parasites of plants, animals and fungi. The overwhelming majority of these (,90%) belong to a single order of obligate plant pathogens, the Pucciniales (5Uredinales), or rust fungi. We have assembled a dataset of previously published and newly generated sequence data from two nuclear rDNA genes (large subunit and small subunit) including exemplars from all known major groups in order to test hypotheses about evolutionary relationships among the Pucciniomycotina. The utility of combining nuc-lsu sequences spanning the entire D1-D3 region with complete nuc-ssu sequences for resolution and support of nodes is discussed. Our study confirms Pucciniomycotina as a monophyletic group of Basidiomycota. In total our results support eight major clades ranked as classes (Agaricostilbo- mycetes, Atractiellomycetes, Classiculomycetes, Cryp- tomycocolacomycetes, Cystobasidiomycetes, Microbo- tryomycetes, Mixiomycetes and Pucciniomycetes) and 18 orders.

Movement patterns of young Caribbean reef sharks, Carcharhinus perezi, at Fernando de Noronha Archipelago, Brazil: the potential of marine protected areas for conservation of a nursery ground

Abstract: The movement patterns and long-term site-fidelity of primarily juvenile Caribbean reef sharks, Carcharhinus perezi, were investigated using tag-recapture and automated telemetry at an insular nursery area, the Fernando de Noronha Archipelago, Brazil. Of the 143 externally tagged juvenile sharks (<110 cm), 22 (15.3%) were recaptured between 0 and 5 km from the site of tagging after 5–800 days at liberty, suggesting some site-fidelity in young individuals of this species. Site-fidelity and movement patterns of ten juvenile sharks ranging from 78 to 110 cm total length (TL) and one opportunistically captured adult female (224 cm TL) were also investigated for periods of up to 2 years with an array of automated telemetry receivers. Tagging and telemetry data from both inside and outside a marine protected area (MPA) show that shark abundance and activity is greatest along the part of the archipelago’s coastline least disturbed by human activity. Telemetry tracking also showed that juvenile reef sharks demonstrated a high degree of site-fidelity and occupied specific locations along the coast throughout the year, with some evidence of an increase in activity space with ontogeny. Sharks appeared to range more widely at night and there were no seasonal variations in habitat use. Our results suggest that MPAs may be a useful conservation tool to protect young C. perezi and potentially other reef-dwelling carcharhinid sharks during their early life history.

Low worldwide genetic diversity in the basking shark (Cetorhinus maximus)

Abstract: The basking shark (Cetorhinus maximus) is found in temperate waters throughout the world's oceans, and has been subjected to extensive exploitation in some regions However, little is known about i

Communicating brand personality: Are the websites doing the talking for the top South African Business Schools?

Abstract: This study extends the conceptualisation and measurement of brand personality to the online environment. We contend that websites are an important element of corporate identity management in today's competitive environment. We investigated the websites of South African Business Schools in order to find out what brand personality each school features. Our multistage methodology revealed a measure of business school brand personality that to some extent portrays the dimensions Aaker postulated. This study illustrates a powerful, but simple and relatively inexpensive way business school managers can study communicated brand personality. The results also offer new ways for business schools (and other organisations) to strengthen their brand and market position in a competitive environment. It also is a relatively simple way to differentiate their school in the crowded MBA education marketplace.

The CASE adherence index: A novel method for measuring adherence to antiretroviral therapy

Abstract: The Center for Adherence Support Evaluation (CASE) Adherence Index, a simple composite measure of self-reported antiretroviral therapy (ART) adherence, was compared to a standard three-day self-reported adherence measure among participants in a longitudinal, prospective cross-site evaluation of 12 adherence programs throughout the United States. The CASE Adherence Index, consisting of three unique adherence questions developed for the cross-site study, along with a three-day adherence self-report were administered by interviews every three months over a one-year period. Data from the three cross-site adherence questions (individually and in combination) were compared to three -day self-report data and HIV RNA and CD4 outcomes in cross-sectional analyses. The CASE Adherence Index correlated strongly with the three-day self-reported adherence data (p 10 achieved a 98 cell mean increase in CD4 count over 12 months, compared to a 41 cell increase for those with scores < or =10 (p < 0.05). The CASE Adherence Index is an easy to administer instrument that provides an alternative method for assessing ART adherence in clinical settings.

The Link Between the Quality of the Supervisor–Employee Relationship and the Level of the Employee's Job Satisfaction

Abstract: This study explores Leader–Member Exchange Theory (LMX Theory), which theorizes when leaders and followers have good exchanges or high quality effective LMX relationships, they share mutual trust, feel better, accomplish more, and the overall unit performance within organization is enhanced. The specific focus of this study is on whether high-quality leader member exchange is positively related to job satisfaction, which can lead to positive outcomes for organizations and ultimately provide organizations the solution to remaining competitive in this new economy. The findings were discussed from the perspective of the advantages available to organizations relative to the many positive organizational outcomes that result from high-quality effective LMX and individual job satisfaction for employees.

Knowledge management and the competitive strategy of the firm

Abstract: Purpose – Knowledge management (KM) has emerged as a strategy to improve organizational competitiveness. Our purpose is to identify the relationship between KM and the firm's competitive advantage.Design/methodology/approach – We review the existing literature on KM and strategy formulation. We utilize the resource‐based view approach as a lens for fitting KM with strategic planning. The concept of strategy and KM integration is introduced.Findings – We relate KM strategies to business strategy through a thorough review of the literature.Research limitations/implications – Future research should investigate the circumstances under which KM can create a sustainable competitive advantage within the framework of the RBV. Another area involves the investigation of the degree of integration between the competitive strategy and KM strategy.Practical implications – A very useful source of information for practitioners to refine their thinking about KM and the firm strategic resources. It offers the practitioner ...

A Modeling Study of the Impact of Tropical Instability Waves on the Heat Budget of the Eastern Equatorial Pacific

Abstract: A numerical simulation is used to investigate the mixed layer heat balance of the tropical Pacific Ocean including the equatorial cold tongue and the region of vortices associated with tropical instability waves (TIWs). The study is motivated by a need to quantify the effects that TIWs have on the climatological heat budget of the cold tongue mixed layer; there has been some discrepancy between observations indicating very large equatorward heat transport by TIWs and models that disagree on the full three-dimensional budget. Validation of the model reveals that the TIW-induced circulation patterns are realistic but may have amplitudes about 15% weaker than those in the observations. The SST budget within tropical instabilities is first examined in a frame of reference moving with the associated tropical instability vortices (TIVs). Zonal advection of temperature anomalies and meridional advection of temperature by current anomalies dominate horizontal advection. These effects strongly heat the cold cusps and slightly cool the downwelling areas located at the leading edge of the vortices. Cooling by vertical mixing is structured at the vortex scale and almost compensates for horizontal advective heating in the cold cusps. In contrast to some previous studies, TIW-induced vertical advection is found to be negligible in the SST budget. Cooling by this term is only significant below the mixed layer. The effect of TIWs on the climatological heat budget is then investigated for the region bounded by 2°S–6°N, 160°–90°W, where instabilities are most active. TIWinduced horizontal advection leads to a warming of 0.84°C month 1 , which is of the same order as the 0.77°C month 1 warming effect of atmospheric fluxes, while the mean currents and vertical mixing cool the upper ocean by 0.59°C month 1 and 1.06°C month 1 , respectively. The cooling effect of TIW-induced vertical advection is also negligible in the long-term surface layer heat budget and only becomes significant below the mixed layer. The results above, and in particular the absence of cancellation between horizontal and vertical TIW-induced eddy advection, are robust in three other sensitivity experiments involving different mixing parameterizations and increased vertical resolution.

Form, function and feedbacks in a tidally dominated ooid shoal, Bahamas

Abstract: Although the general aspects of oolitic depositional systems are well documented, seascape-scale (� 10 3 –10 6 m 2 ) patterns of oolitic shoals and the details of processes acting on them are not well understood or quantified. To begin to fill this basic gap in understanding, this paper describes the morphology and hydrodynamics of Lily Bank, a Modern tidally dominated Bahamian ooid shoal. In this study, integrating remote sensing imagery with quantitative, geo-located bathymetrical, hydrological and granulometric data in a Geographic Information System documents geomorphic and sedimentological patterns and facilitates interpreting these patterns in the context of the processes operating in this system.The results of these analyses reveal that parabolic bars up to several kilometres in wavelength and several metres in height form a common morphologic motif, although there is considerable variation on that general theme. The seascape-scale configuration of bars and superimposed sedimentary structures is closely linked to spatial patterns of tidal movements, and includes the presence of mutually evasive flood and ebb channels. Sedimentologically, bars are neither homogenous nor random bodies; instead, granulometric parameters such as sorting and percentage mud vary systematically, as shaped by hydro-geomorphic controls. The best sorted, coarsest ooids are on bar crests, whereas the finest grains are found in the lower energy, deeper interior and flanking regions. In short, results clearly document hydrodynamic-bathymetrical influences on these ooid shoals and their granulometry, linkages akin to siliciclastic analogues. Sedimentological, hydrodynamic and geomorphic observations are consistent with a conceptual model for the formation of parabolic bars in which initial irregularities in nonparabolic bars are enhanced through their effect of focusing flow. Constricted flow leads to higher flow velocities, tidal flow velocity asymmetries, differential net sediment transport and growth of bathymetrical highs. This bathymetrical divergence creates separate paths for flood- and ebb-tides, facilitating emergence of better-developed parabolic forms. The resultant parabolic geometries and component bedforms appear to be either in dynamic equilibrium with both ebb- and flood-tide flows, or evolving toward that state.In exploring patterns and processes within carbonate shoals, this study illustrates some of the first documented insights on quantitative details of morphology and dynamics and in the links between geomorphic framework and grain-size and sorting in an oolitic carbonate system. Assuming a

The Normative Male Alexithymia Scale: Measurement of a Gender-Linked Syndrome

Abstract: This series of studies assessed the psychometric properties of the Normative Male Alexithymia Scale (NMAS), a brief scale designed to assess normative male alexithymia. Exploratory and confirmatory factor analyses using separate samples (n = 248 and 467, respectively) indicated that the NMAS consist

A genetic algorithm using hyper-quadtrees for low-dimensional k-means clustering

Abstract: The k-means algorithm is widely used for clustering because of its computational efficiency. Given n points in d-dimensional space and the number of desired clusters k, k-means seeks a set of k-cluster centers so as to minimize the sum of the squared Euclidean distance between each point and its nearest cluster center. However, the algorithm is very sensitive to the initial selection of centers and is likely to converge to partitions that are significantly inferior to the global optimum. We present a genetic algorithm (GA) for evolving centers in the k-means algorithm that simultaneously identifies good partitions for a range of values around a specified k. The set of centers is represented using a hyper-quadtree constructed on the data. This representation is exploited in our GA to generate an initial population of good centers and to support a novel crossover operation that selectively passes good subsets of neighboring centers from parents to offspring by swapping subtrees. Experimental results indicate that our GA finds the global optimum for data sets with known optima and finds good solutions for large simulated data sets.

Increasing minority research participation through community organization outreach.

Abstract: Recruitment is one of the most significant challenges in conducting research with ethnic minority populations. Establishing relationships with organizations that serve ethnic minority communities can facilitate recruitment. To create a successful recruitment process, a strategic plan of action is necessary prior to implementing community outreach efforts. For this study population of women who were HIV+ and recovering from substance abuse disorder, the authors found that establishing trust with community organizations that serve these women allows for a productive referral relationship. Although the majority of women in this study are African American, the authors were particularly challenged in recruiting Hispanic women. This article presents a recruitment process model that has facilitated our recruitment efforts and has helped the authors to organize, document, and evaluate their community out-reach strategies. This model can be adopted and adapted by nurses and other health researchers to enhance engagement of minority populations.

Rickettsia sibirica Isolation from a Patient and Detection in Ticks, Portugal

Abstract: We report the first isolation of Rickettsia sibirica (strain mongolotimonae) from the blood of a patient and detection by polymerase chain reaction (PCR) of the rickettsia in a Rhipicephalus pusillus tick collected from a dead mongoose (Herpestes ichneumon) in the Alentejo region, Portugal. We describe also the first PCR detection of a new Rickettsia strain that is related to R. sibirica.

Clinical and microbiological effect of calcium hydroxide protection in indirect pulp capping in primary teeth.

Abstract: Purpose To evaluate clinically and microbiologically the effect of calcium hydroxide (CH) on carious dentin on primary teeth submitted to indirect pulp capping (IPC). Methods Twenty 4-7 year-old subjects with 42 treated teeth participated in the study. The treatment consisted of incomplete excavation of the demineralized dentin, application of a CH or gutta-percha (GP) layer and sealing with a resin-based composite for 4-7 months. After cavity preparation and sealing, the dentin was evaluated clinically (color and consistency) and microbiologically. Dentin samples were cultured on blood agar under aerobic and anaerobic conditions, in Mitis Salivarius agar and Rogosa SL agar. Results 39 teeth (20 in the CH Group and 19 in the GP Group) were reopened 4-7 months post-treatment for clinical and microbiological evaluation. In all teeth, the initial demineralized dentin was wet and soft or leathery. In the CH Group, 10% of the lesions were yellow, 80% light brown and 10% dark brown and in the GP Group, 94.7% were light brown and 5.3% dark brown. After treatment, the dentin was dry, 90% (Group CH) and 84.2% (Group GP) were dark brown. The final consistency was either leathery or hard. Three samples in the CH Group and five in Group GP changed from soft to leathery; only one sample (GP) remained leathery. 85% in the CH Group and 68.4% in GP Group turned hard after treatment. All bacterial counts decreased significantly by the end of treatment. In the CH Group, the bacterial (Log10 CFU + 1) anaerobic growth decreased from 4.84 +/- 1.31 to 1.35 +/- 1.54, aerobic from 4.09 +/- 1.04 to 0.92 +/- 1.30 and lactobacilli from 3.24 +/- 1.22 to 0.36 +/- 0.89, respectively; the mutans streptococci from 2.05 +/- 1.84 to 0.14 +/- 0.60. In GP Group, anaerobic growth decreased from 5.22 +/- 0.96 to 2.02 +/- 1.65 and aerobic from 4.23 +/- 1.37 to 1.08 +/- 1.29 and lactobacilli from 2.06 +/- 1.81 to 0.00 +/- 0.00, respectively; the mutans streptococci from 3.16 +/- 1.59 to 0.28 +/- 0.84.

Cytogenetic and molecular biomonitoring of a Portuguese population exposed to pesticides

Abstract: Widespread use of pesticides in agriculture represents a threat not only to the environment but also to human populations exposed to them Many of these compounds are capable of inducing mutations in DNA and lead to several diseases including cancer In the present study, cytogenetic damage in peripheral lymphocytes from 33 farmers of Oporto district (Portugal) exposed to pesticides was evaluated by means of micronuclei (MN), sister chromatid exchange (SCE) and chromosomal aberrations (CA) In addition, effect of polymorphic genes of xenobiotic metabolizing enzymes (GSTM1, GSTT1, GSTP1, CYP2E1 and EPHX1) was also evaluated A non-exposed group from the same area and with same demographic characteristics without exposure to genotoxic compounds was studied and data obtained from both groups was compared MN and SCE frequencies were significantly higher in the exposed group (P < 0005) In what concerns CA results, no significant differences were observed It was possible to relate a specific working environment (greenhouses) with higher levels of genetic damage Use of personal protective equipment revealed to be important to prevent exposure and diminish genetic damage inflicted by pesticides Allele frequencies of studied polymorphic genes obtained in this study are similar to the ones described by other authors for Caucasian populations Despite the low number of subjects, results suggest that low mEH (microsomal epoxide hydrolase) activity as well as GSTT1 positive genotype are associated with increased cytogenetic damage

The Value of Telephone Support Groups Among Ethnically Diverse Caregivers of Persons With Dementia

Abstract: Purpose: Dementia caregiving is a rapidly growing public health problem. Logistical problems prevent many caregivers from utilizing available interventions. This article provides a demonstration of the usefulness of technology for conducting telephone-based support groups in ethnically diverse dementia caregivers. Design and Methods: Participants were 41 White American and Cuban American dementia caregivers participating at the Miami site of the Resources for Enhancing Alzheimer's Caregiver Health (known as REACH) program. Support groups were conducted over the telephone in English and Spanish as appropriate. Results: Eighty-one percent of the participants found the group "valuable," largely because of the social and emotional support and useful information obtained from other group members. The majority of caregivers also reported that their participation had increased their knowledge and skills as caregivers. Implications: The findings demonstrate that telecommunications technology can overcome the often formidable logistical problems faced by both English- and Spanish-speaking caregivers, and it can provide benefits similar to those obtained in face-to-face support groups.

Eigenvalue Inequalities for Matrix Product

Abstract: We present a family of eigenvalue inequalities for the product of a Hermitian matrix and a positive-semidefinite matrix. Our theorem contains or extends some existing results on trace and eigenvalues

Medication compliance and disease exacerbation in patients with asthma: a retrospective study of managed care data.

Abstract: Background Compliance with asthma medications probably results in improved outcomes, but few studies have examined this relationship. Objective To examine the association between medication compliance and exacerbation in asthmatic patients. Methods Retrospective analysis of a managed care database. The 97,743 participants (aged 6-99 years; mean age, 32.8 years) had asthma and prescriptions for controller medications. Compliance with the index medication (the first controller medication prescribed) was measured using 2 methods: medication possession ratio (MPR), calculated for 365 days after the index date, and number of prescriptions for each index medication. Exacerbation was defined as 1 or more emergency department visits or hospitalizations within 1 year of the index date. Multivariate models were used to determine the odds of exacerbation based on relative compliance for each definition of compliance. Results Based on the median MPR, more-compliant patients were less likely to experience exacerbation than less-compliant patients (odds ratio, 0.94; 95% confidence interval, 0.91-0.97; P P Conclusion More-compliant asthmatic patients were significantly less likely to experience exacerbation than less-compliant asthmatic patients. These findings demonstrate the importance of improving medication compliance among asthmatic patients to impact outcomes.

Teaching Social Software with Social Software.

Abstract: This article explores how the current wave of information and communication technologies (ICTs) known as social software can enable new forms of study and research, preparing students to participate in networks where knowledge is collectively constructed and shared. This approach to learning, which I call distributed research, might be attractive to educators because it exhibits three comparable advantages to those associated with problem-based learning (cf. Watson 2002; De Vry and Watson 2003). First, it engages students in learning to learn by having them assume some of the responsibility for integrating and maintaining the social software systems that allow learning to happen. Second, it promotes the benefits of working cooperatively with tools that facilitate the aggregation and organization of knowledge while at the same time demonstrating that the diversity of individual research interests enhances learning for all. And last, it helps students develop practical research skills that they need in a world where knowledge construction and dissemination make increasing use of online information networks. In short, social software allows students to participate in distributed research communities that extend spatially beyond their classroom and school, temporally beyond a particular class session or term, and technologically beyond the tools and resources that the school makes available to the students.

Uses and Potentials of Wikis in the Classroom

Abstract: As Prensky (2001) observes, "Our students have changed radically. Today's students are no longer the people our educational system was designed to teach" (1). Prensky sees today's students as digital natives while most of today's teachers remain digital immigrants. In particular, today's educators are acculturated to a print paradigm while students are increasingly products of a digitally-based secondary-oral paradigm. Happily for educators, electronic and cyber technologies can potentially combine the best aspects of both print and secondary-oral paradigms, allowing educators to move freely across the print-oral continuum. One cyber technology enabling this movement is the wiki, a unique interface where information is not fixed (as in a print model) but fluid and flexible to meet the needs of the community (as in the pre-literate age). In this article we describe how teaching and learning have changed across oral, print, and secondary-oral paradigms; in turn, after addressing some controversies over the use of wikis as scholarly and educational resources, we advocate the use of wikis as a teaching and learning tool.

The Mechanism of Plasmid Curing in Bacteria

Abstract: Bacterial plasmids have a major impact on metabolic function. Lactose fermentation of E. coli or hemolysin B transporter expressed by the plasmids that carry these respective genes could be readily obviated by heterocyclic compounds that readily bind to plasmid DNA. These compounds could also reverse the resistance to antibiotics of E. coli , Enterobacter, Proteus, Staphylococcus and Yersinia strains by eliminating plasmids. However, the frequency and extent of this effect was significantly less than might have been expected based on a complex interaction with plasmid DNA. The effects of heterocyclic compounds on the plasmids responsible for the virulence of Yersinia and A. tumefaciens, or on nodulation, nitrogen fixation of Rhizobia accounted for the elimination of 0.1 to 1.0 % of plasmids present in the populations studied. Bacterial plasmids can be eliminated from bacterial species grown as pure or mixed bacterial cultures in the presence of sub-inhibitory concentrations of non-mutagenic heterocyclic compounds. The antiplasmid action of the compounds depends on the chemical structure of amphiphillic compounds having a planar ring system with substitution in the L-molecular region. A symmetrical π-electron conjugation at the highest occupied molecular orbitals favours the antiplasmid effect. The antiplasmid effect of heterocyclic compounds is expressed differentially in accordance with the structural form of the DNA to which they bind. In this manner extrachromosomal plasmid DNA that exists in a superhelical state binds more compound than its linear or open-circular form; and least to the chromosomal DNA of the bacterium, that carries the plasmid. It can also be noted that these compounds are not mutagenic and their antiplasmid effects correlate with the energy of HOMO-orbitals. Plasmid elimination is considered also to take place in ecosystems containing numerous bacterial species. This opens up a new perspective in rational drug design against bacterial plasmids. The inhibition of conjugational transfer of antibiotic resistance plasmid can be exploited to reduce the spread of antibiotic resistance plasmid in the ecosystem. Inhibition of plasmid replication at various stages, as shown in the rolling circle model (replication, partition, conjugal transfer) may also be the theoretical basis for the elimination of bacterial virulence in the case of plasmid mediated pathogenicity and antibiotic resistance. The large number of compounds tested for antiplasmid effects provides opportunities for QSAR studies in order to find a correlation between the antiplasmid effect and the supramolecular chemistry of these plasmid curing compounds. Plasmid elimination in vitro provides a method of isolating plasmid free bacteria for biotechnology without any risk of inducing mutations.