Effect of nanorope waviness on the effective moduli of nanotube sheets

Using a micromechanics approach, we recently investigated the theoretical limits on achievable moduli in nanotube mats by stiffening of bonds. However, the waviness intrinsic to many manufacturing processes also clearly plays an important role in stiffness of these materials. To study the effect of waviness on mechanical properties, we modeled fiber segments as sinusoids, generated networks comprised of these fibers, and performed simulations of deformations of the networks. In contradiction of classical work by Kallmes and Corte [Tappi J. 43, 737 (1960)], we found the number of fiber crossings in these networks to be independent of fiber waviness, leading to identification of the number of fiber crossings as a necessary and sufficient parameter to specify network geometry, for either wavy or straight fibers. Our mechanical modeling results suggest that reducing the waviness of nanotube ropes would significantly improve Young’s moduli in these materials. However, reduction of waviness would not produce the improvements achievable with higher bond density; for random sheets, assuring connections among all intersecting ropes appears to be the most direct route toward improving the overall sheet properties. There remains a persistent discrepancy between statistically predicted bond densities and physical bond densities, based on moduli of these materials. © 2004 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71274/2/JAPIAU-95-9-5027-1.pd

Statistical geometry of random fibrous networks, revisited: Waviness, dimensionality, and percolation

Waviness alters both geometric and mechanical properties of stochastic fibrous networks and significantly affects overall mechanical response, but few results are available in the literature on the subject. In this work, we explore the importance of the dimension of constituent fibers (1D vs 2D) in determination of percolation thresholds, and other fundamental statistical properties of fibers having geometric waviness, in adaptation of classical theories on random lattices to practical applications, including analysis of nanotube ropes and collagen bundles. Although the so-called “curl ratio” clearly affects the statistical properties, as evaluated by Kallmes and Corte a few decades ago, we have found some results in this classic work to be inaccurate for systems containing fibers of moderate waviness. Our main findings include the independence of the mean number of crossings with regard to waviness, as well as the nonlinear dependence of probability of intersection on waviness. Our investigation of percolation in wavy fiber networks reveals that the percolation threshold is significantly increased, with increasing curl ratio. In addition, several nontrivial results related to network properties of infinite straight lines are also described, some of which are believed to have wide applications in practice. © 2004 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69927/2/JAPIAU-96-3-1318-1.pd

IL-2 Regulates Expression of C-MAF in Human CD4 T Cells

Blockade of IL-2R with humanized anti-CD25 Abs, such as daclizumab, inhibits Th2 responses in human T cells. Recent murine studies have shown that IL-2 also plays a significant role in regulating Th2 cell differentiation by activated STAT5. To explore the role of activated STAT5 in the Th2 differentiation of primary human T cells, we studied the mechanisms underlying IL-2 regulation of C-MAF expression. Chromatin immunoprecipitation studies revealed that IL-2 induced STAT5 binding to specific sites in the C-MAF promoter. These sites corresponded to regions enriched for markers of chromatin architectural features in both resting CD4 and differentiated Th2 cells. Unlike IL-6, IL-2 induced C-MAF expression in CD4 T cells with or without prior TCR stimulation. TCR-induced C-MAF expression was significantly inhibited by treatment with daclizumab or a JAK3 inhibitor, R333. Furthermore, IL-2 and IL-6 synergistically induced C-MAF expression in TCR-activated T cells, suggesting functional cooperation between these cytokines. Finally, both TCR-induced early IL4 mRNA expression and IL-4 cytokine expression in differentiated Th2 cells were significantly inhibited by IL-2R blockade. Thus, our findings demonstrate the importance of IL-2 in Th2 differentiation in human T cells and support the notion that IL-2R–directed therapies may have utility in the treatment of allergic disorders

Mechanical properties of nanotube sheets: Alterations in joint morphology and achievable moduli in manufacturable materials

Nanotube sheets, or “bucky papers,” have been proposed for use in actuating, structural and electrochemical systems, based in part on their potential mechanical properties. Here, we present results of detailed simulations of networks of nanotubes/ropes, with special emphasis on the effect of joint morphology. We perform detailed simulations of three-dimensional joint deformation, and use the results to inform simulations of two-dimensional (2D) networks with intertube connections represented by torsion springs. Upper bounds are established on moduli of nanotube sheets, using the 2D Euler beam-network simulations. Comparisons of experimental and simulated response for HiPco-nanotube and laser-ablated nanotube sheets, indicate that ∼2–30-fold increases in moduli may be achievable in these materials. Increasing the numbers of interrope connections appears to be the best target for improving nanotube sheet stiffnesses in materials containing straight segments. © 2004 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70283/2/JAPIAU-95-8-4335-1.pd

Castor bean organelle genome sequencing and worldwide genetic diversity analysis

Castor bean is an important oil-producing plant in the Euphorbiaceae family. Its high-quality oil contains up to 90% of the unusual fatty acid ricinoleate, which has many industrial and medical applications. Castor bean seeds also contain ricin, a highly toxic Type 2 ribosome-inactivating protein, which has gained relevance in recent years due to biosafety concerns. In order to gain knowledge on global genetic diversity in castor bean and to ultimately help the development of breeding and forensic tools, we carried out an extensive chloroplast sequence diversity analysis. Taking advantage of the recently published genome sequence of castor bean, we assembled the chloroplast and mitochondrion genomes extracting selected reads from the available whole genome shotgun reads. Using the chloroplast reference genome we used the methylation filtration technique to readily obtain draft genome sequences of 7 geographically and genetically diverse castor bean accessions. These sequence data were used to identify single nucleotide polymorphism markers and phylogenetic analysis resulted in the identification of two major clades that were not apparent in previous population genetic studies using genetic markers derived from nuclear DNA. Two distinct sub-clades could be defined within each major clade and large-scale genotyping of castor bean populations worldwide confirmed previously observed low levels of genetic diversity and showed a broad geographic distribution of each sub-clade

Workshop on breeding for Striga resistance in cereals

The phanerogamous root parasite Striga hermonthica (Del.) Benth. causes major yield reductions in the principal cereal crops of semi-arid Africa. A workshop on breeding for Striga resistance in cereals was held at the International Institute of Tropical Agriculture (1 IT A) in I badan. Nigeria, from 18 to 20August 1999. The meeting was organized by the International Crops Research Institute for the Semi-A rid Tropics (ICRISAT}. I IT A, the University of Hohenheim. Eberhard-Karls University of Tubingen, and the Rockefeller Foundation. Funding was provided by the Bundesministerium fur wirtschaftliche Zusammenarbeit (BMZ), Germany, the Rockefeller Foundation, and the International Fund for Agricultural Development (IFAD). The 56 participants comprised 26 cereal breeders or weed specialists from national agricultural research systems (NARS) of 17 African countries, and 30 scientists or representatives from the International Maize and Wheat Improvement Center (CIMMYT), Centre de cooperation internationale en recherche agronomique pour le developpement (CIRAD), ICRISAT, IITA. John Innes Centre (JIC), the Natural Resources Institute (NRI). Pan African Striga Control Network (PASCON), ProAgro Seed Company, the Rockefeller Foundation, Cornell University, University of Hohenheim, Purdue University, University of Sheffield. University of Tubingen, West Africa Rice Development Association (WARDA), and the Weizmann Institute of Science

Performance of a Novel Low-Cost, Instrument-Free Plasma Separation Device for HIV Viral Load Quantification and Determination of Treatment Failure in People Living with HIV in Malaysia: a Diagnostic Accuracy Study

HIV viral load (VL) testing is the recommended method for monitoring the response of people living with HIV and receiving antiretroviral therapy (ART). The availability of standard plasma VL testing in low- and middle-income countries (LMICs), and access to this testing, are limited by the need to use fresh plasma. Good specimen collection methods for HIV VL testing that are applicable to resource-constrained settings are needed. We assessed the diagnostic performance of the filtered dried plasma spot (FDPS), created using the newly developed, instrument-free VLPlasma device, in identifying treatment failure at a VL threshold of 1,000 copies/ml in fresh plasma. Performance was compared with that of the conventional dried blood spot (DBS). Venous blood samples from 201 people living with HIV and attending an infectious disease clinic in Malaysia were collected, and HIV VL was quantified using fresh plasma (the reference standard), FDPS, and DBS specimens. VL testing was done using the Roche Cobas AmpliPrep/Cobas TaqMan v2.0 assay. At a threshold of 1,000 copies/ml, the diagnostic performance of the FDPS was superior (sensitivity, 100% [95% confidence interval {CI}, 89.1 to 100%]; specificity, 100% [95% CI, 97.8 to 100%]) to that of the DBS (sensitivity, 100% [95% CI, 89.4 to 100%]; specificity, 36.8% [95% CI, 29.4 to 44.7%]) (P 0.001). A stronger correlation was observed between the FDPS VL and the plasma VL (r 0.94; P 0.001) than between the DBS VL and the plasma VL (r 0.85; P 0.001). The mean difference in VL measures between the FDPS and plasma (plasma VL minus FDPS VL) was 0.127 log10 copies/ml (standard deviation [SD], 0.32), in contrast to – 0.95 log10 copies/ml (SD, 0.84) between the DBS and plasma. HIV VL measurement using the FDPS outperformed that with the DBS in identifying treatment failure at a threshold of 1,000 copies/ml and compared well with the quantification of VL in plasma. The FDPS can be an attractive alternative to fresh plasma for improving access to HIV VL monitoring among people living with HIV on ART in LMICs

Cumulative Risk, Age at Onset, and Sex-Specific Differences for Developing End-Stage Renal Disease in Young Patients With Type 1 Diabetes: A Nationwide Population-Based Cohort Study

OBJECTIVE This study aimed to estimate the current cumulative risk of end-stage renal disease (ESRD) due to diabetic nephropathy in a large, nationwide, population-based prospective type 1 diabetes cohort and specifically study the effects of sex and age at onset. RESEARCH DESIGN AND METHODS In Sweden, all incident cases of type 1 diabetes aged 0-14 years and 15-34 years are recorded in validated research registers since 1977 and 1983, respectively. These registers were linked to the Swedish Renal Registry, which, since 1991, collects data on patients who receive active uremia treatment. Patients with years duration of type 1 diabetes were included (n = 11,681). RESULTS During a median time of follow-up of 20 years, 127 patients had developed ESRD due to diabetic nephropathy. The cumulative incidence at 30 years of type 1 diabetes duration was low, with a male predominance (4.1% [95% CI 3.1-5.3] vs. 2.5% [1.7-3.5]). In both male and female subjects, onset of type I diabetes before 10 years of age was associated with the lowest risk of developing ESRD. The highest risk of ESRD was found in male subjects diagnosed at age 20-34 years (hazard ratio 3.0 [95% CI 1.5-5.7]). In female subjects with onset at age 20-34 years, the risk was similar to patients diagnosed before age 10 years. CONCLUSIONS The cumulative incidence of ESRD is exceptionally low in young type 1 diabetic patients in Sweden. There is a striking difference in risk for male compared with female patients. The different patterns of risk by age at onset and sex suggest a role for puberty and sex hormones