The granular Blasius problem

We consider the steady flow of a granular current over a uniformly sloped surface that is smooth upstream (allowing slip for x<0) but rough downstream (imposing a no-slip condition on x>0), with a sharp transition at $x=0$. This problem is similar to the classical Blasius problem, which considers the growth of a boundary layer over a flat plate in a Newtonian fluid that is subject to a similar step change in boundary conditions. Our discrete particle model simulations show that a comparable boundary-layer phenomenon occurs for the granular problem: the effects of basal roughness are initially localised at the base but gradually spread throughout the depth of the current. A rheological model can be used to investigate the changing internal velocity profile. The boundary layer is a region of high shear rate and therefore high inertial number $I$; its dynamics is governed by the asymptotic behaviour of the granular rheology for high values of the inertial number. The \unicode[STIX]{x1D707}(I) rheology (Jop et al., Nature, vol. 441 (7094), 2006, pp. 727–730) asserts that \text{d}\unicode[STIX]{x1D707}/\text{d}I=O(1/I^{2}) as $I\rightarrow \infty$, but current experimental evidence is insufficient to confirm this. We show that this rheology does not admit a self-similar boundary layer, but that there exist generalisations of the \unicode[STIX]{x1D707}(I) rheology, with different dependencies of \unicode[STIX]{x1D707}(I) on $I$, for which such self-similar solutions do exist. These solutions show good quantitative agreement with the results of our discrete particle model simulations.J.M.F.T. is funded by an EPSRC Studentship (EP/M508007/1) N.M.V. is a Royal Society Dorothy Hodgkin Research Fellow (DH120121)

Coccidioidomycosis Incidence in Arizona Predicted by Seasonal Precipitation

The environmental mechanisms that determine the inter-annual and seasonal variability in incidence of coccidioidomycosis are unclear. In this study, we use Arizona coccidioidomycosis case data for 1995–2006 to generate a timeseries of monthly estimates of exposure rates in Maricopa County, AZ and Pima County, AZ. We reveal a seasonal autocorrelation structure for exposure rates in both Maricopa County and Pima County which indicates that exposure rates are strongly related from the fall to the spring. An abrupt end to this autocorrelation relationship occurs near the the onset of the summer precipitation season and increasing exposure rates related to the subsequent season. The identification of the autocorrelation structure enabled us to construct a “primary” exposure season that spans August-March and a “secondary” season that spans April–June which are then used in subsequent analyses. We show that October–December precipitation is positively associated with rates of exposure for the primary exposure season in both Maricopa County (R = 0.72, p = 0.012) and Pima County (R = 0.69, p = 0.019). In addition, exposure rates during the primary exposure seasons are negatively associated with concurrent precipitation in Maricopa (R = −0.79, p = 0.004) and Pima (R = −0.64, p = 0.019), possibly due to reduced spore dispersion. These associations enabled the generation of models to estimate exposure rates for the primary exposure season. The models explain 69% (p = 0.009) and 54% (p = 0.045) of the variance in the study period for Maricopa and Pima counties, respectively. We did not find any significant predictors for exposure rates during the secondary season. This study builds on previous studies examining the causes of temporal fluctuations in coccidioidomycosis, and corroborates the “grow and blow” hypothesis

Kinetics of the hydrogen abstraction ·C2H5 + alkane → C2H6 + alkyl reaction class: an application of the reaction class transition state theory

This paper presents an application of the reaction class transition state theory (RC-TST) to predict thermal rate constants for hydrogen abstraction reactions at alkane by the C2H5 radical on-the-fly. The linear energy relationship (LER), developed for acyclic alkanes, was also proven to hold for cyclic alkanes. We have derived all RCTST parameters from rate constants of 19 representative reactions, coupling with LER and the barrier height grouping (BHG) approach. Both the RC-TST/LER, where only reaction energy is needed, and the RC-TST/BHG, where no other information is needed, can predict rate constants for any reaction in this reaction class with satisfactory accuracy for combustion modeling. Our analysis indicates that less than 50% systematic errors on the average exist in the predicted rate constants using either the RC-TST/LER or RC-TST/BHG method, while in comparison with explicit rate calculations, the differences are within a factor of 2 on the average. The results also show that the RC-TST method is not sensitive to the choice of density functional theory used

Robust message routing for mobile (wireless) ad hoc networks.

This report describes the results of research targeting improvements in the robustness of message transport in wireless ad hoc networks. The first section of the report provides an analysis of throughput and latency in the wireless medium access control (MAC) layer and relates the analysis to the commonly used 802.11 protocol. The second section describes enhancements made to several existing models of wireless MAC and ad hoc routing protocols; the models were used in support of the work described in the following section. The third section of the report presents a lightweight transport layer protocol that is superior to TCP for use in wireless networks. In addition, it introduces techniques that improve the performance of any ad hoc source routing protocol. The fourth section presents a novel, highly scalable ad hoc routing protocol that is based on geographic principles but requires no localization hardware

Phase I dose-escalation and pharmacokinetic study of temozolomide (SCH 52365) for refractory or relapsing malignancies

Temozolomide, an oral cytotoxic agent with approximately 100% bioavailability after one administration, has demonstrated schedule-dependent clinical activity against highly resistant cancers. Thirty patients with minimal prior chemotherapy were enrolled in this phase I trial to characterize the drug's safety, pharmacokinetics and anti-tumour activity, as well as to assess how food affects oral bioavailability. To determine dose-limiting toxicities (DLT) and the maximum tolerated dose (MTD), temozolomide 100–250 mg m−2 was administered once daily for 5 days every 28 days. The DLT was thrombocytopenia, and the MTD was 200 mg m−2 day−1. Subsequently, patients received the MTD to study how food affects the oral bioavailability of temozolomide. When given orally once daily for 5 days, temozolomide was well tolerated and produced a non-cumulative, transient myelosuppression. The most common non-haematological toxicities were mild to moderate nausea and vomiting. Clinical activity was observed against several advanced cancers, including malignant glioma and metastatic melanoma. Temozolomide demonstrated linear and reproducible pharmacokinetics and was rapidly absorbed (mean Tmax ~1 h) and eliminated (mean t1/2 = 1.8 h). Food produced a slight reduction (9%) in absorption of temozolomide. Temozolomide 200 mg m−2 day−1 for 5 days, every 28 days, is recommended for phase II studies. © 1999 Cancer Research Campaig

CHMP1A encodes an essential regulator of BMI1-INK4A in cerebellar development

Charged multivesicular body protein 1A (CHMP1A; also known as chromatin-modifying protein 1A) is a member of the ESCRT-III (endosomal sorting complex required for transport-III) complex but is also suggested to localize to the nuclear matrix and regulate chromatin structure. Here, we show that loss-of-function mutations in human CHMP1A cause reduced cerebellar size (pontocerebellar hypoplasia) and reduced cerebral cortical size (microcephaly). CHMP1A-mutant cells show impaired proliferation, with increased expression of INK4A, a negative regulator of stem cell proliferation. Chromatin immunoprecipitation suggests loss of the normal INK4A repression by BMI in these cells. Morpholino-based knockdown of zebrafish chmp1a resulted in brain defects resembling those seen after bmi1a and bmi1b knockdown, which were partially rescued by INK4A ortholog knockdown, further supporting links between CHMP1A and BMI1-mediated regulation of INK4A. Our results suggest that CHMP1A serves as a critical link between cytoplasmic signals and BMI1-mediated chromatin modifications that regulate proliferation of central nervous system progenitor cells

Epidemiological Characteristics of 2009 (H1N1) Pandemic Influenza Based on Paired Sera from a Longitudinal Community Cohort Study

Steven Riley and colleagues analyze a community cohort study from the 2009 (H1N1) influenza pandemic in Hong Kong, and found that more children than adults were infected with H1N1, but children were less likely to progress to severe disease than adults