Dual Carriage Research Articles

Diverse temperate bacteriophage carriage in Clostridium difficile 027 strains.

BackgroundThe hypervirulent Clostridium difficile ribotype 027 can be classified into subtypes, but it unknown if these differ in terms of severity of C. difficile infection (CDI). Genomic studies of C. difficile 027 strains have established that they are rich in mobile genetic elements including prophages. This study combined physiological studies, electron microscopy analysis and molecular biology to determine the potential role of temperate bacteriophages in disease and diversity of C. difficile 027.Methodology/Principal FindingsWe induced prophages from 91 clinical C. difficile 027 isolates and used transmission electron microscopy and pulsed-field gel electrophoresis to characterise the bacteriophages present. We established a correlation between phage morphology and subtype. Morphologically distinct tailed bacteriophages belonging to Myoviridae and Siphoviridae were identified in 63 and three isolates, respectively. Dual phage carriage was observed in four isolates. In addition, there were inducible phage tail-like particles (PT-LPs) in all isolates. The capacity of two antibiotics mitomycin C and norfloxacin to induce prophages was compared and it was shown that they induced specific prophages from C. difficile isolates. A PCR assay targeting the capsid gene of the myoviruses was designed to examine molecular diversity of C. difficile myoviruses. Phylogenetic analysis of the capsid gene sequences from eight ribotypes showed that all sequences found in the ribotype 027 isolates were identical and distinct from other C. difficile ribotypes and other bacteria species.Conclusion/SignificanceA diverse set of temperate bacteriophages are associated with C. difficile 027. The observed correlation between phage carriage and the subtypes suggests that temperate bacteriophages contribute to the diversity of C. difficile 027 and may play a role in severity of disease associated with this ribotype. The capsid gene can be used as a tool to identify C. difficile myoviruses present within bacterial genomes.

RESILIENT BEHAVIOUR OF ASPHALT CONCRETE UNDER REPEATED LOADING & EFFECTS OF TEMPERATURE

In this paper resilient behavior of asphalt concrete mixes were studied by varying temperature & time of loading to understand the pavement behavior under Pakistani climatic conditions & to address the problem according to mode of distress. The common cause of pavement distress in Pakistan is rutting, which initiates due to uncontrolled axle load & large variation in temperature. Indirect Tensile and creep tests were carried out using Universal Testing Machine (UTM 5P) on the cores taken from Islamabad-Peshawar Motorway Section (M1), IJP Principal road dual carriage way (Links Islamabad to Grand Trunk Road) & mixes prepared in the laboratory. Both sections had been opened for traffic on 2 nd , November, 2004. Polymer Modified Bitumen (PMB) has been used on M1 and is a unique opportunity to compare the behavior of in situ Asphalt Concrete mixes with & without PMB under same temperature & loading conditions. The results of laboratory tests on asphalt concrete cores (from M1 & IJP road) under the influence of load, environmental and mix variables are presented in this paper.

Technical and dosimetric considerations in IMRT treatment planning for large target volumes

The maximum width of an intensity-modulated radiotherapy (IMRT) treatment field is usually smaller than the conventional maximum collimator opening because of design limitations inherent in some multileaf collimators (MLCs). To increase the effective field width, IMRT fluences can be split and delivered with multiple carriage positions. However, not all treatment-planning systems and MLCs support this technique, and if they do, the maximum field width in multiple carriage position delivery is still significantly less than the maximum collimator opening. For target volumes with dimensions exceeding the field size limit for multiple carriage position delivery, such as liver tumors or other malignancies in the abdominal cavity, IMRT treatment can be accomplished with multiple isocenters or with an extended treatment distance. To study dosimetric statistics of large field IMRT planning, an elliptical volume was chosen as a target within a cubic phantom centered at a depth of 7.5 cm. Multiple three-field plans (one AP and two oblique beams with 160° between them to avoid parallel opposed geometry) with constraints designed to give 100% dose to the elliptical target were developed. Plans were designed with a single anterior field with dual carriage positions, or with the anterior field split into two fields with separate isocenters 8 cm apart with the beams being forcibly matched at the isocenter or with a 1 cm, 2 cm, 3 cm, and 4 cm overlap. The oblique beams were planned with a single carriage position in all cases. All beams had a nominal energy of 6 MV. In the dual isocenter plans, jaws were manually fixed and dose constraints remained unaltered. Dosimetric statistics were studied for plans developed for treatment delivery using both dynamic leaf motion (sliding window) and multiple static segments (step and shoot) with the number of segments varying from 5 to 30. All plans were analyzed based on the dose homogeneity in the isocenter plane, 2 cm anterior and 2 cm posterior to it, along with their corresponding dose-volume histograms (DVHs). All the dual isocenter plans had slight underdosage anterior to the match point and slight overdosage posterior to it, while the dual carriage plan had a nice blending of the dose distribution without the accompanying hot or cold spots. Based on the dose statistics, it was noted that the dual isocenter plans can be clinically acceptable if they have at least a 3-cm overlap. In the case of step and shoot IMRT, the number of segments used in a dual carriage plan was found to affect the overall plan dosimetric indices. PACS number: 87.53.Tf

Technical and dosimetric considerations in IMRT treatment planning for large target volumes

The maximum width of an intensity‐modulated radiotherapy (IMRT) treatment field is usually smaller than the conventional maximum collimator opening because of design limitations inherent in some multileaf collimators (MLCs). To increase the effective field width, IMRT fluences can be split and delivered with multiple carriage positions. However, not all treatment‐planning systems and MLCs support this technique, and if they do, the maximum field width in multiple carriage position delivery is still significantly less than the maximum collimator opening. For target volumes with dimensions exceeding the field size limit for multiple carriage position delivery, such as liver tumors or other malignancies in the abdominal cavity, IMRT treatment can be accomplished with multiple isocenters or with an extended treatment distance. To study dosimetric statistics of large field IMRT planning, an elliptical volume was chosen as a target within a cubic phantom centered at a depth of 7.5 cm. Multiple three‐field plans (one AP and two oblique beams with 160° between them to avoid parallel opposed geometry) with constraints designed to give 100% dose to the elliptical target were developed. Plans were designed with a single anterior field with dual carriage positions, or with the anterior field split into two fields with separate isocenters 8 cm apart with the beams being forcibly matched at the isocenter or with a 1 cm, 2 cm, 3 cm, and 4 cm overlap. The oblique beams were planned with a single carriage position in all cases. All beams had a nominal energy of 6 MV. In the dual isocenter plans, jaws were manually fixed and dose constraints remained unaltered. Dosimetric statistics were studied for plans developed for treatment delivery using both dynamic leaf motion (sliding window) and multiple static segments (step and shoot) with the number of segments varying from 5 to 30. All plans were analyzed based on the dose homogeneity in the isocenter plane, 2 cm anterior and 2 cm posterior to it, along with their corresponding dose‐volume histograms (DVHs). All the dual isocenter plans had slight underdosage anterior to the match point and slight overdosage posterior to it, while the dual carriage plan had a nice blending of the dose distribution without the accompanying hot or cold spots. Based on the dose statistics, it was noted that the dual isocenter plans can be clinically acceptable if they have at least a 3‐cm overlap. In the case of step and shoot IMRT, the number of segments used in a dual carriage plan was found to affect the overall plan dosimetric indices.PACS number: 87.53.Tf

Economic feasibility of the proposed Second Forth Road Bridge using Public Private Partnership procurement

The existing Forth Road Bridge near Edinburgh in Scotland at present carries 24 million vehicles annually, which is twice its design capacity. The need for a second Forth Road Bridge is discussed in this paper. There is currently a proposal for design and construction of the second Forth Road Bridge crossing. Some organisations are in favour of the project and yet others are against it. If the project were sanctioned, it would be private sector funded under the government’s PFI/PPP programme. This paper provides an economic evaluation of the proposed second Forth Road Bridge crossing. Firstly, a review of studies carried out on the traffic characteristics across the Forth is provided. Secondly, a critical analysis of the economic tools and techniques available for cost‐benefit analysis is given. The concept of cost of capital for government projects is also discussed and distinguished from cost of borrowing. The paper then provides present values of expected revenues from toll charges supported by extensive sensitivity studies for various assumptions regarding changes in toll levels, concession periods, future traffic growth levels and cost of capital. The main conclusions of the study are that the scheme is economically viable subject to the following limitations. If only Northbound traffic is tolled, this would require quadrupling of the current toll levels for the expected revenues to be adequate to fund design, construction and maintenance costs of a second standard bridge crossing and approach roads over a 30‐year concession period. If both Northbound and Southbound traffic were tolled, the present toll levels would need to be doubled on award of the concession contract and increased annually by the Retail Price Index (RPI) for the scheme to be economically viable. If the new crossing is to include the possibility of a heavy rail link under the dual carriage way, the expected present values of toll revenues provided they are increased as suggested above would be adequate only to fund design and construction costs of the new crossing and maintenance of both bridges. The project as whole would only be economically viable if the public sector funded the design, construction and maintenance costs of the required tunnels and approach roads.

Association between carriage of Streptococcus pneumoniae and Staphylococcus aureus in Children.

Widespread pneumococcal conjugate vaccination may bring about epidemiologic changes in upper respiratory tract flora of children. Of particular significance may be an interaction between Streptococcus pneumoniae and Staphylococcus aureus, in view of the recent emergence of community-acquired methicillin-resistant S aureus. To examine the prevalence and risk factors of carriage of S pneumoniae and S aureus in the prevaccination era in young children. Cross-sectional surveillance study of nasopharyngeal carriage of S pneumoniae and nasal carriage of S aureus by 790 children aged 40 months or younger seen at primary care clinics in central Israel during February 2002. Carriage rates of S pneumoniae (by serotype) and S aureus; risk factors associated with carriage of each pathogen. Among 790 children screened, 43% carried S pneumoniae and 10% carried S aureus. Staphylococcus aureus carriage among S pneumoniae carriers was 6.5% vs 12.9% in S pneumoniae noncarriers. Streptococcus pneumoniae carriage among S aureus carriers was 27.5% vs 44.8% in S aureus noncarriers. Only 2.8% carried both pathogens concomitantly vs 4.3% expected dual carriage (P =.03). Risk factors for S pneumoniae carriage (attending day care, having young siblings, and age older than 3 months) were negatively associated with S aureus carriage. Streptococcus pneumoniae carriage, specifically of vaccine-type strains, is negatively associated with S aureus carriage in children. The implications of these findings in the pneumococcal vaccine era require further investigation.

Broadcast, Cable And Digital Must Carry: The Other Digital Divide

As television broadcasters make the transition from analog to digital broadcasting, questions arise as to how must-carry law, which generally requires cable operators to carry the signals of all full-power, local television broadcasters, should apply to broadcasters' digital signals. There are three components to the digital must-carry issue: dual carriage, total carriage and the carriage of program-related content. This article examines the arguments for and against revisions of the law to require any of these three. It concludes that neither dual carriage nor total carriage should be required by law, but that the FCC should develop a flexible definition of program-related content entitled to mandatory carriage to allow the meaning of what constitutes a single channel of programming to evolve with technology.