338 research outputs found
Chromosomal anchoring of linkage groups and identification of wing size QTL using markers and FISH probes derived from microdissected chromosomes in Nasonia(Pteromalidae : Hymenoptera)
Nasonia vitripennis is a small parasitic hymenopteran with a 50-year history of genetic work including linkage mapping with mutant and molecular markers. For the first time we are now able to anchor linkage groups to specific chromosomes. Two linkage maps based on a hybrid cross (N. vitripennis x N. longicornis) were constructed using STS, RAPID and microsatellite markers, where 17 of the linked STS markers were developed from single microdissected banded chromosomes. Based on these microdissections we anchored all linkage groups to the five chromosomes of N. vitripennis. We also verified the chromosomal specificity of the microdissection through in situ hybridization and linkage analyses. This information and technique will allow us in the future to locate genes or QTL detected in different mapping populations efficiently and fast on homologous chromosomes or even chromosomal regions. To test this approach we asked whether QTL responsible for the wing size in two different hybrid crosses (N. vitripennis x N. longicornis and N. vitripennis x N. giraulti) map to the same location. One QTL with a major effect was found to map to the centromere region of chromosome 3 in both crosses. This could indicate that indeed the same gene/s is involved in the reduction of wing in N. vitripennis and N. longicornis. Copyright (C) 2003 S. Karger AG, Basel
Concrete Pavement Joint Deterioration
Concrete pavements are an important part of our national infrastructure. In recent years the relatively small number of reported joints deteriorating prematurely in concrete pavements around Indiana has increased. Changes over the past 45 years in INDOT specification, pavement materials, designs and construction practices, and current de-icing materials were examined and related to the durability of concrete at the joints of existing pavements. A survey of concrete pavements across the state revealed that no pavements from the two southern districts less than 40 years old showed this distress except in more recently placed patches.
Cores were retrieved from the joints and mid-panel of 11 pavement sections that represented different materials, ages, construction, deicer exposure, and different levels of deterioration, from non-deteriorated concrete to concrete with severe deterioration at the joints. The pavement base drained well at the mid-panel of most pavements but was reduced at the joints for over half the pavements with the most severe joint deterioration associated with the slowest drainage. None of the concrete had an air void system that met all the criteria recommended for FT durable concrete but was better at the mid-panel than at the joints. Infilling and lining of the entrained air voids with ettringite and some Friedel’s salt was more common near the joints and could account for the reduced air void system. The FT testing did not correlate directly with the air void parameters but generally mid-panel samples did test as more durable than joints. Evidence from the presence of unhydrated cement grains suggested that the concrete at the joint face was not fully cured. One pavement section that did not have fly ash had worse deterioration than the panels nearby that had fly ash and calcium hydrate was more noticeable in the concrete from joints with severe deterioration.
Several variables were identified that influence the durability of the concrete at the joints and there may be other variables that were beyond the scope or capacity of this study. In summary this study identified the following variables likely influenced the durability of the concrete at the joints: the drainability of the base at the joints, original air void system, reduced air void parameters due to lining and infilling of the air voids with secondary minerals, poor hydration of the concrete at the joint face and increased moisture at the joint
Cascading ecological effects from local extirpation of an ecosystem engineer in the Arava desert
The extinction of a single species from a local community may carry little cost in terms of species diversity, yet its loss eliminates its biotic and abiotic interactions. We describe such a scenario in the Arava desert, where different cultural and law enforcement practices exclude Dorcas gazelles (Gazella dorcas (Linnaeus, 1758)) from the Jordanian side of the border while protecting their populations on the Israeli side. We found that gazelles break the soil crust, formed in desert systems after annual flooding, thereby creating patches of loose and cooler sand that are used by pit-building antlions (Neuroptera: Myrmeleontidae). When we artificially broke the soil crust on both sides of the border, we found a significant increase in antlion density in these patches, but only on the Israeli side. On the Jordanian side, where no gazelles have been observed since the early 1980s, no antlions colonized either control or manipulated plots. Additional choice/no-choice feeding experiments, in which we offered antlions to lizards and birds, revealed that the effect of humans on gazelles cascades farther, as antlions serve as a palatable food source for both groups. Thus, the human-mediated loss of nontrophic interactions between gazelles and antlions cascades to the loss of trophic interactions between antlions and their predators
The Center for Centering Dome
The Center for Centering seeks to create a large-scale healing center, conducive to individual centering of the mind and body. This mobile installation provides a relaxing, enclosed space while still maintaining a connection to the outdoors. The clients liked the idea of having a pop-up installation that could be easily set up as a touring display. With a deadline for installation looming in June 2022, a team of students had five months to design and manufacture the structure.
In winter 2022, the students developed custom geometry to minimize the number of individual parts and built a ¼ scale model of the design. In spring 2022, the students digitally modeled each part and manufactured the designs in the woodshop, culminating in the construction of the pavilion. What made this project remarkable was the students\u27 opportunity to work with real clients, meet real deadlines, and learn how their design impacted construction while manufacturing the structure all by themselves. From creating countless digital models to troubleshooting tolerances and manufacturing mishaps, this project was the epitome of Cal Poly’s “Learn by Doing” motto
Using Recycled Concrete as Aggregate in Concrete Pavements to Reduce Materials Cost
The main objective of this project was to evaluate the effects of using aggregate produced from crushed concrete pavement as a replacement for natural (virgin) coarse aggregate in pavement mixtures. A total of ten different concrete mixtures containing recycled concrete aggregate (RCA) were designed to meet the requirements of Indiana Department of Transportation (INDOT) specifications. These included three different RCA replacement levels (30%, 50% and 100% by weight of the natural coarse aggregate) and two different cementitious systems (plain system – Type I portland cement only and fly ash system – 80% of Type I portland cement and 20% of ASTM C 618 Class C fly ash). The scope of the project included the evaluation and comparison of several properties of RCA and natural aggregates, evaluation and analysis of the effects of RCA on concrete properties, and modification of aggregate gradations and mixture composition in an attempt to improve the properties of RCA concrete.
All ten mixtures were first produced in the laboratory (trial batches) and were subsequently reproduced in the commercial ready-mixed concrete plant. Each mixture produced in the ready-mixed plant was used to prepare several types of specimens for laboratory testing. The tests performed on fresh concrete included determination of slump and entrained air content. The mechanical properties of the hardened concrete were assessed by conducting compressive strength, flexural strength, modulus of elasticity and Poisson’s ratio tests.
Concrete durability was assessed using a wide array of measurements, including: rapid chloride permeability (RCP), rapid chloride migration (RCM), electrical impedance spectroscopy (EIS), surface resistivity, free shrinkage, water absorption test, freeze-thaw resistance and scaling resistance.
The test results indicated that the properties of plain (no fly ash) concrete mixtures with 30% RCA as coarse aggregate were very comparable to (in some cases even better than) those of the control concrete (0% RCA). Although mixtures with 50% RCA showed a reduction in durability and mechanical properties of up to 36%, the test results still met INDOT’s specifications requirements. The mechanical properties of plain concretes made with 100% RCA were measurably lower (16%-25%) than those of the control concrete. It should be pointed out, however, that these properties were still above the minimums required by INDOT’s specifications except for one mixture in which the w/c was increased to 0.47 to achieve workability. The use of fly ash improved the strength and durability of RCA concrete, especially at later ages. In particular, the properties of concrete with 50% RCA coarse aggregate were similar to the properties of control concrete. Similarly, the mechanical and durability properties of the mixture with 100% RCA coarse aggregate and 20% fly ash were better than those of a similar mixture prepared without fly ash. Even though, when compared to the fly ash concrete with 100% virgin aggregate the mechanical and durability properties of the 100% RCA concrete were up to 19% and 35% lower, it still met minimum requirements imposed by INDOT’s specifications.
Once the testing of the original ten types of concrete mixtures was completed, six additional concrete mixtures were developed and produced in the laboratory using aggregate with a modified gradation (with respect to the gradation of the aggregates used in the original mixtures). These mixtures were used to study whether the virgin and RCA aggregates can be used in different proportions to produce an “optimized blend” which will improve one (or more) of the concrete characteristics. The test results obtained from the six additional mixtures indicated that modifying the aggregate gradation did not have beneficial effects with respect to either compressive or flexural strength values. This failure to improve concrete strength with modified aggregate gradation may have been due, at least in part, to the quality of the source of aggregate that was used to modify the gradation.
Considering the limited scope of this study (only one source of RCA and two natural aggregate sources were used), it is recommended that the amount of RCA coarse aggregate be limited to 30% in plain concrete and to 50% in fly ash concrete to ensure the adequate quality of the pavement concrete
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Synthesis: Accelerating Implementation of Research Findings to Reduce Potential Concrete Pavement Joint Deterioration
Distress has recently been observed in the joints of some concrete pavements, primarily in the wet-freeze states. This distress often begins in longitudinal joints, followed by transverse joints and results in the significant loss of material from the joint area. Although it may only affect approximately 10% of the concrete pavements system-wide, it greatly reduces the service life and increases maintenance costs of the pavements it effects. Primary issues that emerged from studies on this phenomenon include the importance of the timing of joint sawing, the width of the joint opening, degree of concrete or joint sealing, drainage and degree of saturation of the concrete at the joint, quality of the air void system, role of deicing chemicals, quality of curing, and the degree of restraint at the joint. Although this broad collection of issues implies that we still lack complete understanding of all causes of joint deterioration, it also makes it pretty clear that the observed damage is a result of combination of several factors. This study synthesizes completed research related to concrete pavements joint deterioration and provides information to advance the knowledge and understanding of the variables involved in in this deterioration process and suggests the best practices that can lead to its reduction or mitigation
Automatic System for the D.C. High Voltage Qualification of the Superconducting Electrical Circuits of the LHC Machine
A d.c. high voltage test system has been developed to verify automatically the insulation resistance of the powering circuits of the LHC. In the most complex case, up to 72 circuits share the same volume inside cryogenic lines. Each circuit can have an insulation fault versus any other circuit or versus ground. The system is able to connect up to 80 circuits and apply a voltage up to 2 kV D.C. The leakage current flowing through each circuit is measured within a range of 1 nA to 1.6 mA. The matrix of measurements allows characterizing the paths taken by the currents and locating weak points of the insulation between circuits. The system is composed of a D.C. voltage source and a data acquisition card. The card is able to measure with precision currents and voltages and to drive up to 5 high voltage switching modules offering 16 channels each. A LabVIEW application controls the system for an automatic and safe operation. This paper describes the hardware and software design, the testing methodology and the results obtained during the qualification of the LHC superconducting circuits
Carbon supported CdSe nanocrystals
Insights to the mechanism of CdSe nanoparticle attachment to carbon nanotubes
following the hot injection method are discussed. It was observed that the
presence of water improves the nanotube coverage while Cl containing media are
responsible for the shape transformation of the nanoparticles and further
attachment to the carbon lattice. The experiments also show that the mechanism
taking place involves the right balance of several factors, namely, low
passivated nanoparticle surface, particles with well-defined crystallographic
facets, and interaction with an organics-free sp2 carbon lattice. Furthermore,
this procedure can be extended to cover graphene by quantum dots.Comment: 5 pages, 5 figure
Signatures of balancing selection in toll-like receptor (TLRs) genes – novel insights from a free-living rodent
Correction to: Scientific Reports https://doi.org/10.1038/s41598-018-26672-2, published online 30 May 2018 “The work was supported by grant no. DEC-2012/07/B/NZ8/00058 from the Polish National Science Centre to A.K. Field studies were funded by grant MNiI 2P04C09827 „Badania naturalnych źródeł zarażenia mikropasożytów patogennych dla człowieka” to AB. We are thankful to Dr. hab W. Babik who provided access to an Illumina MiSeq platform, and to K. Dudek who prepared the Nextera library. Special thanks to A. Biedrzycka for her valuable comments on the final version of the manuscript. We also would like to thank two anonymous reviewers for their valuable comments that helped to improve the manuscript.”Peer reviewedPublisher PD
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