Tunable assembly of host-guest colloidal crystals

Entropy compartmentalization provides new self-assembly routes to colloidal host-guest (HG) structures. Leveraging host particle shape to drive the assembly of HG structures has only recently been proposed and demonstrated. However, the extent to which the guest particles can dictate the structure of the porous network of host particles has not been explored. In this work, by modifying only the guest shape, we show athermal, binary mixtures of star-shaped host particles and convex polygon-shaped guest particles assemble as many as five distinct crystal structures, including rotator and discrete rotator guest crystals, two homoporous host crystals, and one heteroporous host crystal. Edge-to-edge alignment of neighboring stars results in the formation of three distinct pore motifs, whose preferential formation is controlled by the size and shape of the guest particles. Finally, we confirm, via free volume calculations, that assembly is driven by entropy compartmentalization, where the hosts and guests contribute differently to the free energy of the system; free volume calculations also explain differences in assembly based on guest shape. These results provide guest design rules for assembling colloidal HG structures, especially on surfaces and interfaces.

Molecular characterization of adenocarcinomas arising in the urinary bladder following augmentation cystoplasty: a multi-institutional study

Development of malignancy is a rare complication following augmentation cystoplasty, and the majority of tumors observed in this setting are adenocarcinomas. Here, we sought to genetically profile these tumors by targeted DNA sequencing of a multi-institutional cohort of adenocarcinomas that developed in the urinary bladder following augmentation cystoplasty. Carcinomas arising in the urinary bladder of patients with history of augmentation cystoplasty were obtained from 4 major academic institutions, with cases diagnosed as urothelial carcinoma excluded from the study. The cases were analyzed using a DNA sequencing panel that includes 529 genes and genome-wide copy number assessment. The most frequently altered genes included TP53, KRAS, and MYC, and the vast majority of cases demonstrated mutational profiles consistent with gastrointestinal adenocarcinomas. One case demonstrated an EML4::ALK fusion together with an MSH3 frameshift mutation and hypermutated phenotype, characteristic of a rare but aggressive subtype of colorectal adenocarcinoma that may benefit from targeted ALK inhibition therapy. Importantly, six other tumors in the cohort also had potentially targetable molecular alterations, involving ATM (2 cases), BRCA1 (2 cases), EGFR (1 case), and ERBB2 (1 case). To our knowledge, this study represents the most comprehensive molecular characterization to date of adenocarcinomas arising in the urinary bladder following augmentation cystoplasty. Despite the unique environment of the augmented tissue, the resulting tumors demonstrate a spectrum of driver mutations similar to that of primary gastrointestinal adenocarcinomas. Importantly, molecular alterations potentially amenable to targeted therapy were identified in the majority of cases.

Newtonian Event-Chain Monte Carlo and Collision Prediction with Polyhedral Particles

Polyhedral nanocrystals are building blocks for nanostructured materials that find applications in catalysis and plasmonics. Synthesis efforts and self-assembly experiments have been assisted by computer simulations that predict phase equilibria. Most current simulations employ Monte Carlo methods, which generate stochastic dynamics. Collective and correlated configuration updates are alternatives that promise higher computational efficiency and generate trajectories with realistic dynamics. One such alternative involves event-chain updates and has recently been proposed for spherical particles. In this contribution, we develop and apply event-chain Monte Carlo for hard convex polyhedra. Our simulation makes use of an improved computational geometry algorithm XenoSweep, which predicts sweep collision in a particularly simple way. We implement Newtonian event chains in the open-source general-purpose particle simulation toolkit HOOMD-blue for serial and parallel simulation. The speedup over state-of-the-art Monte Carlo is between a factor of 10 for nearly spherical polyhedra and a factor of 2 for highly aspherical polyhedra. Finally, we validate the Newtonian event-chain algorithm by applying it to a current research problem, the multistep nucleation of two classes of hard polyhedra.

Shape-driven entropic self-assembly of an open, reconfigurable, binary host-guest colloidal crystal

Entropically driven self-assembly of hard anisotropic particles, where particle shape gives rise to emergent valencies, provides a useful perspective for the design of nanoparticle and colloidal systems. Hard particles self-assemble into a rich variety of crystal structures, ranging in complexity from simple close-packed structures to structures with 432 particles in the unit cell. Entropic crystallization of open structures, however, is missing from this landscape. Here, we report the self-assembly of a two-dimensional binary mixture of hard particles into an open host-guest structure, where nonconvex, triangular host particles form a honeycomb lattice that encapsulates smaller guest particles. Notably, this open structure forms in the absence of enthalpic interactions by effectively splitting the structure into low- and high-entropy sublattices. This is the first such structure to be reported in a two-dimensional athermal system. We discuss the observed compartmentalization of entropy in this system, and show that the effect of the size of the guest particle on the stability of the structure gives rise to a reentrant phase behavior. This reentrance suggests the possibility for a reconfigurable colloidal material, and we provide a proof-of-concept by showing the assembly behavior while changing the size of the guest particles in situ. Our findings provide a strategy for designing open colloidal crystals, as well as binary systems that exhibit co-crystallization, which have been elusive thus far.

Adult Plant Leaf Rust Resistance in AC Taber Wheat Maps to Chromosomes 2BS and 3BS

AC Taber is a hard red spring wheat cultivar that has had long-lasting resistance to the leaf rust fungus Puccinia triticina. The objective of this study was to determine the chromosome location of the leaf rust resistance genes in AC Taber. The leaf rust-susceptible cultivar Thatcher was crossed with AC Taber to develop an F₆ recombinant inbred line (RIL) population. The RILs and parents were evaluated for segregation of leaf rust resistance in five field plot tests and in two seedling tests to race BBBDB of P. triticina. A genetic map of the RIL population was developed using 90,000 single nucleotide polymorphism markers with the Illumina Infinium iSelect 90K wheat bead array. Quantitative trait loci (QTLs) with significant effects for lower leaf rust severity in the field plot tests were found on chromosomes 2BS and 3BS. The same QTLs also had significant effects for lower infection type in seedlings to leaf rust race BBBDB. The gene on 2BS was the adult plant resistance gene Lr13, and the gene on 3BS mapped to the same region as the adult plant resistance gene Lr74 and other QTLs for leaf rust resistance. Kompetitive allele-specific PCR assay markers linked to the 2BS and 3BS regions were developed and should be useful for marker-based selection of these genes.

Invasive poorly differentiated adenocarcinoma of the bladder following augmentation cystoplasty: a multi-institutional clinicopathological study

Augmentation cystoplasty is a surgical procedure used in the management of patients with neurogenic bladder. This procedure involves anastomosis of the bladder with gastrointestinal grafts, including portions of ileum, colon, or stomach. A rare but important complication of augmentation cystoplasty is the development of malignancy. The majority of malignancies arising in this setting have been described in case reports. A search for cases of non-urothelial carcinoma following augmentation cystoplasty was conducted through the urological pathology files of four major academic institutions. Ten cases were identified, including six cystoprostatectomy/cystectomy, two partial cystectomy, and two transurethral resection of bladder tumour specimens. The mean patient age at diagnosis was 47 years (range 27-87 years). The male:female ratio was 4:6. The tumours tended to present at an advanced stage; four cystoprostatectomy/cystectomy cases were categorised as pT3a, one was categorised as pT3b, and one was categorised as pT4a. Lymph node metastases were present in all cases which had lymph node excision (range 1-16 positive nodes per case). The majority of cases (90%) were predominantly characterised by a poorly differentiated adenocarcinoma with signet ring cell features. Other morphological features included mucinous features (30%), plasmacytoid features (20%), enteric/villous architecture (10%), and large cell undifferentiated morphology (10%). This is the largest study to date on the clinicopathological features of invasive non-urothelial carcinoma of the bladder following augmentation cystoplasty. The tumours are typically poorly differentiated adenocarcinoma, with diffuse signet ring cell features, aggressive, and present at high stage. Further molecular characterisation may provide additional insights into the pathogenesis of this entity.

Thatcher wheat line RL6149 carries Lr64 and a second leaf rust resistance gene on chromosome 1DS

The leaf rust resistance gene Lr64 in the Thatcher wheat RL6149 was mapped to chromosome 6AL with SNP and KASP markers and a second leaf rust resistance gene was mapped to chromosome 1DS. RL6149, a near-isogenic line of Thatcher wheat, carries leaf rust resistance gene Lr64 on chromosome arm 6AL. The objective of this study was to develop molecular markers that can be easily used to select wheat lines with Lr64. RL6149 was crossed with Thatcher and F₂ plants derived from a single F₁ plant were advanced to F₆ lines by single seed descent. The 100 F₇ recombinant inbred lines (RIL) were inoculated with two races of P.triticina that differed widely for virulence in order to identify resistant and susceptible RIL. Thirty RIL that differed for resistance and the parental lines were genotyped with the 90 K Infinium iSelect single nucleotide polymorphism (SNP) array to find closely linked markers with Lr64. Seven linked SNPs on chromosome arm 6AL were converted into Kompetitive Allele Specific PCR (KASP) markers that were genotyped on the 100 RIL. A genetic linkage map for the seven KASP markers spanned 19.1 cM on chromosome arm 6AL. KASP marker K-IWB59855 was tightly linked to Lr64. A second unexpected gene for leaf rust resistance also segregated in the F₇ lines. Four KASP markers that spanned 18.6 cM located the gene on chromosome 1DS. The KASP marker K-IWB38437 was tightly linked to the second leaf rust resistance gene.

Symmetries in hard polygon systems determine plastic colloidal crystal mesophases in two dimensions

Orientational ordering is a necessary step in the crystallization of molecules and anisotropic colloids. Plastic crystals, which are possible mesophases between the fluid and fully ordered crystal, are translationally ordered but exhibit no long range orientational order. Here, we study the two-dimensional phase behavior of hard regular polygons with edge number n = 3-12. This family of particles provides a model system to isolate the effect of shape and symmetry on the existence of plastic crystal phases. We show that the symmetry group of the particle, G, and the symmetry group of the local environment in the crystal, H, together determine plastic colloidal crystal phase behavior in two dimensions. If G contains completely the symmetry elements of H, then a plastic crystal phase is absent. If G and H share some but not all nontrivial symmetry elements, then a plastic crystal phase exists with preferred particle orientations that recover the absent symmetry elements of the crystal; we call this phase the discrete plastic crystal phase. If G and H share no nontrivial symmetry elements, then a plastic crystal phase exists without preferred orientations, which we call an indiscrete plastic crystal.

Views from the clinic: Healthcare provider perspectives on whole genome sequencing in paediatrics

Whole genome sequencing (WGS) is a transformative technology which promises improved diagnostic rates compared to conventional genetic testing strategies and tailored approaches to patient care. Due to the practical and ethical complexities associated with using WGS, particularly in the paediatric context, input from a broad spectrum of healthcare providers can guide implementation strategies. We recruited healthcare providers from the largest paediatric academic health science centre in Canada and conducted semi-structured qualitative interviews, exploring experiences with and perceptions of the opportunities and challenges associated with WGS. Interview transcripts were coded and analyzed thematically. Interviews were completed with 14 genetics professionals (geneticists and genetic counsellors) and 15 non-genetics professionals (physician sub-specialists and nurses). Genetics professionals ordered genetic tests more often and reported greater confidence on pre- and post-test genetic counselling compared to non-genetics professionals. Most healthcare providers endorsed WGS when a more specific test was either not available or not likely to yield a diagnosis. While genetics professionals raised concerns regarding the time demands associated with reviewing WGS variants, non-genetics professionals reflected concerns about knowledge and training. Providers' position on reporting secondary variants to parents drew upon but was not limited to the concept of best interests. Taken together, understanding practical and principled matters of WGS from healthcare providers' perspectives can guide ongoing efforts to implement WGS in paediatrics.

Parents perspectives on whole genome sequencing for their children: qualified enthusiasm?

OBJECTIVE

To better understand the consequences of returning whole genome sequencing (WGS) results in paediatrics and facilitate its evidence-based clinical implementation, we studied parents' experiences with WGS and their preferences for the return of adult-onset secondary variants (SVs)-medically actionable genomic variants unrelated to their child's current medical condition that predict adult-onset disease.

METHODS

We conducted qualitative interviews with parents whose children were undergoing WGS as part of the SickKids Genome Clinic, a research project that studies the impact of clinical WGS on patients, families, and the healthcare system. Interviews probed parents' experience with and motivation for WGS as well as their preferences related to SVs. Interviews were analysed thematically.

RESULTS

Of 83 invited, 23 parents from 18 families participated. These parents supported WGS as a diagnostic test, perceiving clear intrinsic and instrumental value. However, many parents were ambivalent about receiving SVs, conveying a sense of self-imposed obligation to take on the 'weight' of knowing their child's SVs, however unpleasant. Some parents chose to learn about adult-onset SVs for their child but not for themselves.

CONCLUSIONS

Despite general enthusiasm for WGS as a diagnostic test, many parents felt a duty to learn adult-onset SVs. Analogous to 'inflicted insight', we call this phenomenon 'inflicted ought'. Importantly, not all parents of children undergoing WGS view the best interests of their child in relational terms, thereby challenging an underlying justification for current ACMG guidelines for reporting incidental secondary findings from whole exome and WGS.

Prediction of histological stage based on cystoscopic appearances of newly diagnosed bladder tumours

INTRODUCTION In the 75-80% of urothelial bladder cancers (UBC) presenting as non-muscle invasive bladder cancer (NMIBC), transurethral resection of bladder tumour (TURBT) is the key treatment and staging procedure. In the 20-25% of patients with muscle invasive bladder cancer (MIBC), further cross-sectional imaging is required to complete the staging process before considering radical treatment. Given the adverse effects of ionising radiation, clinicians identify patients believed to have MIBC, and so requiring further imaging pre-TURBT, at the tumour histology/stage based on the tumour's visual characteristics. There is minimal evidence describing the accuracy of such predictions in newly-diagnosed patients. METHODS Over a 6-year period, a database of patients undergoing resection of newly-diagnosed bladder lesions in a single UK centre was prospectively established. Predictions based on histology were simultaneously recorded, and the accuracy of these predictions of histology/stage subsequently assessed. RESULTS One hundred and twenty two (73.1%) patients with histologically confirmed NMIBC had predictions recorded versus 45 (26.9%) patients with MIBC. Visual assessment predictions of MIBC had a sensitivity of 88.9% (95% confidence interval [CI] 76.5%-95.2%) and a specificity of 91.0% (95% CI 84.6%-94.9%), giving a positive predictive value of 78.4% (95% CI 65.4%-87.5%) and a negative predictive value of 95.7% (95% CI 90.3%-98.1%). CONCLUSIONS We find that visual assessment is accurate in predicting the presence of MIBC. This supports the practice of stratifying patients at the time of initial cystoscopy for those requiring further radiological staging pre-TURBT.

Non-Pharmacological Factors in Drug Therapy—The Inter-Action of Doctor, Patient and Tablet Appearance in the Treatment of Anxiety/Depressive Syndromes

The degree to which placebo response is involved in an active treatment situation in normal clinical practice, and the factors comprising the placebo response, have been analyzed in a study on patients with anxiety/depressive syndromes. Four tablet preparations of different appearance but identical pharmacological activity were used over a three week period, and a comparison of therapeutic benefits between ‘treatments', doctors, and doctor—patient groupings was made, in addition to an analysis of the relationship of patients' self-assessments with their physicians' ratings.

The results showed that although direct pharmacological effect was paramount in determining therapeutic outcome, detailed differences were related to various placebo factors. The similarity between physicians' and patients' ratings tends to decrease during the course of treatment, and possible reasons for this are reviewed in the light of previous work.

Association mapping of North American spring wheat breeding germplasm reveals loci conferring resistance to Ug99 and other African stem rust races

BACKGROUND

The recently identified Puccinia graminis f. sp. tritici (Pgt) race TTKSK (Ug99) poses a severe threat to global wheat production because of its broad virulence on several widely deployed resistance genes. Additional virulences have been detected in the Ug99 group of races, and the spread of this race group has been documented across wheat growing regions in Africa, the Middle East (Yemen), and West Asia (Iran). Other broadly virulent Pgt races, such as TRTTF and TKTTF, present further difficulties in maintaining abundant genetic resistance for their effective use in wheat breeding against this destructive fungal disease of wheat. In an effort to identify loci conferring resistance to these races, a genome-wide association study was carried out on a panel of 250 spring wheat breeding lines from the International Maize and Wheat Improvement Center (CIMMYT), six wheat breeding programs in the United States and three wheat breeding programs in Canada.

RESULTS

The lines included in this study were grouped into two major clusters, based on the results of principal component analysis using 23,976 SNP markers. Upon screening for adult plant resistance (APR) to Ug99 during 2013 and 2014 in artificial stem rust screening nurseries at Njoro, Kenya and at Debre Zeit, Ethiopia, several wheat lines were found to exhibit APR. The lines were also screened for resistance at the seedling stage against races TTKSK, TRTTF, and TKTTF at USDA-ARS Cereal Disease Laboratory in St. Paul, Minnesota; and only 9 of the 250 lines displayed seedling resistance to all the races. Using a mixed linear model, 27 SNP markers associated with APR against Ug99 were detected, including markers linked with the known APR gene Sr2. Using the same model, 23, 86, and 111 SNP markers associated with seedling resistance against races TTKSK, TRTTF, and TKTTF were identified, respectively. These included markers linked to the genes Sr8a and Sr11 providing seedling resistance to races TRTTF and TKTTF, respectively. We also identified putatively novel Sr resistance genes on chromosomes 3B, 4D, 5A, 5B, 6A, 7A, and 7B.

CONCLUSION

Our results demonstrate that the North American wheat breeding lines have several resistance loci that provide APR and seedling resistance to highly virulent Pgt races. Using the resistant lines and the SNP markers identified in this study, marker-assisted resistance breeding can assist in development of varieties with elevated levels of resistance to virulent stem rust races including TTKSK.

Shape allophiles improve entropic assembly

We investigate a class of "shape allophiles" that fit together like puzzle pieces as a method to access and stabilize desired structures by controlling directional entropic forces. Squares are cut into rectangular halves, which are shaped in an allophilic manner with the goal of re-assembling the squares while self-assembling the square lattice. We examine the assembly characteristics of this system via the potential of mean force and torque, and the fraction of particles that entropically bind. We generalize our findings and apply them to self-assemble triangles into a square lattice via allophilic shaping. Through these studies we show how shape allophiles can be useful for assembling and stabilizing desired phases with appropriate allophilic design.

Infection and Colonization of Several Bermudagrasses by Ophiosphaerella korrae

Bermudagrass (Cynodon spp.) is the most commonly used turfgrass in the southern United States where it is severely affected by spring dead spot (SDS) caused by Ophiosphaerella herpotricha, O. korrae, and O. narmari. In this study, infection of bermudagrass roots and stolons by O. korrae was characterized using a transformant that expressed the red fluorescent protein tdTomato. Roots of interspecific hybrid cultivars Midlawn and Tifway 419, C. transvaalensis accessions Uganda and 3200, and C. dactylon cultivar U3 were inoculated and observed from 2 to 14 days postinoculation (DPI) while stolons were observed from 2 to 22 DPI. For all five cultivars tested, a similar level of root colonization was observed; however, differences were observed in the rate of necrosis development. Necrosis of Tifway 419 and Midlawn tissues was evident at 2 DPI, in Uganda and 3200 at 8 DPI, and in U3 necrosis was often absent as late as 14 DPI. The fungus rapidly penetrated the root epidermis and colonized the cortex of all cultivars by 4 DPI. Colonization of stele tissues by O. korrae was rare in hybrid cultivars but common in C. transvaalensis and C. dactylon accessions. On intact stolons, the fungus did not penetrate the epidermis 22 DPI though epidermal necrosis was evident on the surface of only the hybrid bermudagrasses. Wounded stolons became necrotic in all cultivars. Infection and colonization of various bermudagrasses by O. korrae was found to be similar to that by O. herpotricha, suggesting that host genetic resistance may be used for effective management of SDS caused by both species.

Predictive genetic testing for adult-onset disorders in minors: a critical analysis of the arguments for and against the 2013 ACMG guidelines

The publication of the ACMG recommendations has reignited the debate over predictive testing for adult-onset disorders in minors. Response has been polarized. With this in mind, we review and critically analyze this debate. First, we identify long-standing inconsistencies between consensus guidelines and clinical practice regarding risk assessment for adult-onset genetic disorders in children using family history and molecular analysis. Second, we discuss the disparate assumptions regarding the nature of whole genome and exome sequencing underlying arguments of both supporters and critics, and the role these assumptions play in the arguments for and against reporting. Third, we suggest that implicit differences regarding the definition of best interests of the child underlie disparate conclusions as to the best interests of children in this context. We conclude by calling for clarity and consensus concerning the central foci of this debate.

Phase behavior and complex crystal structures of self-assembled tethered nanoparticle telechelics

Motivated by growing interest in the self-assembly of nanoparticles for applications such as photonics, organic photovoltaics, and DNA-assisted designer crystals, we explore the phase behavior of tethered spherical nanoparticles. Here, a polymer tether is used to geometrically constrain a pair of nanoparticles creating a tethered nanoparticle "telechelic". Using simulation, we examine how varying architectural features, such as the size ratio of the two end-group nanospheres and the length of the flexible tether, affects the self-assembled morphologies. We demonstrate not only that this hybrid building block maintains the same phase diversity as linear triblock copolymers, allowing for a variety of nanoparticle materials to replace polymer blocks, but also that new structures not previously reported are accessible. Our findings imply a robust underlying ordering mechanism is common among these systems, thus allowing flexibility in synthesis approaches to achieve a target morphology.

Fluoroscopic sentinel events in neuroendovascular procedures: how to screen, prevent, and address occurrence

Radiation-induced skin injury during fluoroscopic procedures has been recently addressed by The Joint Commission, which defined prolonged fluoroscopy resulting in a cumulative peak skin dose of ≥15 Gy to a single field as a sentinel event (FSE). Neuroendovascular procedures can be associated with a high radiation skin dose and present risks such as potential FSEs. Managing these risks is the responsibility of the interventional neuroradiologist. In this review, we discuss hospital policies needed for screening and preventing FSEs, methods for minimizing radiation-induced skin injury, and actions necessary to address potential FSEs once they have occurred.

Hard-disk equation of state: first-order liquid-hexatic transition in two dimensions with three simulation methods

We report large-scale computer simulations of the hard-disk system at high densities in the region of the melting transition. Our simulations reproduce the equation of state, previously obtained using the event-chain Monte Carlo algorithm, with a massively parallel implementation of the local Monte Carlo method and with event-driven molecular dynamics. We analyze the relative performance of these simulation methods to sample configuration space and approach equilibrium. Our results confirm the first-order nature of the melting phase transition in hard disks. Phase coexistence is visualized for individual configurations via the orientational order parameter field. The analysis of positional order confirms the existence of the hexatic phase.

Interspecific nuclear-cytoplasmic compatibility controlled by genes on group 1 chromosomes in durum wheat

Triticum longissimum cytoplasm is incompatible with the T. turgidum nuclear genome. Two nuclear genes, scs and Vi, derived from the nuclear genome of T. timopheevii and by a spontaneous mutation, respectively, restore nuclear-cytoplasmic compatibility, normal plant vigor, and male fertility in these alloplasmic genotypes. The objectives of this study were (i) to determine the chromosomal locations of scs and Vi; (ii) to identify DNA markers for scs and Vi; and (iii) to determine the interactions involving the dosage of scs and Vi. Two populations segregating for scs and Vi were produced and scored for seedling vigor (indicating presence of scs) and degree of self-fertility (indicating presence of Vi). Four RFLP markers were mapped near scs. Aneuploid analysis revealed that these markers, and hence the scs gene, are located on the long arm of chromosome 1A. Four RFLP markers were mapped near Vi on 1BS. Results indicated that other factors may be inhibiting the expression of Vi. We determined the dosage of scs and Vi in both populations with the aid of the linked RFLP markers. Individuals with two versus one dose of scs had reduced self-fertility, while individuals with two versus one dose of Vi had similar self-fertility.

SU-E-I-10: Putting Teeth into Your CT Dosimetry Program: Approaches to Cone- Beam Dental/Maxillofacial CT Dosimetry

PURPOSE

To review and compare different approaches to the problem of dosimetry for limited field-of-view (FOV) cone beam CT devices for dental and maxillofacial applications.

METHODS

The determination of patient doses from specialized, cone-beam CT devices for dental and maxillofacial work requires medical physicists to re-evaluate their dosimetry methods. These devices work in cone-beam geometry, with an axial field dimension on the order of the lengths of the standard head CTDI phantom and pencil ionization chamber. They may also utilize less than 360 degree scans, resulting in asymmetrical radiation distributions. This operating regime is far from that for which conventional CT dosimetry was designed, and alternative approaches must be considered. The alternatives include extensions of conventional CT dosimetry currently used for large axial FOV scanners (e.g. the extended CTDI parameter (CTDIe) for the Toshiba Aquillion One with 160 mm axial FOV) and the new method based on point dosimetry measurements recently formalized in AAPM Report TG-111. Conventional, modified-conventional, and TG-111 dosimetry measurements are used in two CT dose phantoms (adult head and pediatric head) to obtain dose indices for the Planmeca ProMax 3D Max dental CT scanner. Surface dose maps are generated using radiochromic film for correlation with the chamber dosimetry.

RESULTS

Results for the three dosimetry approaches are compared for the specific case of the ProMax 3D Max scanner. Strengths and weaknesses of the three measurement paradigms for this type of application are compared.

CONCLUSIONS

The increasing availability of specialized scanners operating in full cone-beam mode will require the clinical medical physicist to be conversant with extensions to the CT dose index methodology suitable for this equipment.

Optimal filling of shapes

We present filling as a type of spatial subdivision problem similar to covering and packing. Filling addresses the optimal placement of overlapping objects lying entirely inside an arbitrary shape so as to cover the most interior volume. In n-dimensional space, if the objects are polydisperse n-balls, we show that solutions correspond to sets of maximal n-balls. For polygons, we provide a heuristic for finding solutions of maximal disks. We consider the properties of ideal distributions of N disks as N→∞. We note an analogy with energy landscapes.

First Detection in North America of Virulence in Wheat Leaf Rust (Puccinia triticina) to Seedling Plants of Wheat with Lr21

Leaf rust resistance gene Lr21 is present in hard red spring wheat (Triticum aestivum) cultivars grown in Minnesota, North Dakota, South Dakota, Manitoba, and Saskatchewan. Isolates of Puccinia triticina, the causal organism of wheat leaf rust, with virulence to this gene have not been previously detected in annual virulence surveys in the United States. (2). In 2010, hard red spring wheat cvs. Faller, RB07 (1), and Glenn, all with Lr21, had 0 to 5% levels of leaf rust severity, which was higher than in previous years in research plots in North Dakota and Minnesota. Leaf rust collections from wheat cultivars and germplasm lines with Lr21 at three locations in Minnesota and North Dakota were increased on plants of the leaf rust susceptible wheat Thatcher and the Thatcher line with Lr21. Single uredinia from the collections were isolated and increased on seedlings of Thatcher. The single uredinial isolates were inoculated to 7- to 8-day-old seedling plants of the set of 19 differential lines that are currently used in the leaf rust virulence surveys (2). Thatcher lines with Lr3bg, Lr14b, Lr20, and Lr23 were also tested. The isolates were also inoculated to seedling plants of hard red spring wheat cultivars with Lr21: Glenn, Steele-ND, Faller, RB07, Amidon, AC Cora, and McKenzie (3). Previous standardized methods for growing seedling plants, increase of rust isolates, inoculation, incubation, and evaluation of infection types (IT) were used (2). All tests with the Thatcher differential lines and the cultivars with Lr21 were repeated at least twice. Virulence phenotypes were described based on virulence to the 19 differentials in the P. triticina virulence nomenclature system used in the United States. (2). Two virulence phenotypes, TFBJQ and TFBGQ, with virulence to Lr21 were found at the three locations. TFBJQ is virulent (IT 3 to 4) to genes Lr1, 2a, 2c, 3, 10, 14a, 14b, 20, 21, 24, 26, 28, and avirulent (IT 0 to 2⁺) to genes Lr3ka, Lr3bg, Lr9, Lr11, Lr17, Lr18, Lr30, LrB, and Lr39/41. TFBGQ was avirulent to Lr14a and Lr20, but identical to TFBJQ for virulence and avirulence to the other resistance genes. Isolates of both phenotypes were virulent on seedlings of Faller, Glenn, RB07 (1), Steele-ND, AC Cora, and Amidon. McKenzie had IT of 2⁺ due to the additional presence of Lr16 (3). Both TFBJQ and TFBGQ have intermediate IT of 2⁺ to Lr16; IT 2⁺3 to Lr23, and are completely virulent to Lr1, Lr2a, and Lr10 that are present in hard red spring wheat cultivars. Both phenotypes have high IT to Lr24 and Lr26 that are present in soft red winter wheat and hard red winter wheat cultivars. The Lr21 virulent phenotypes likely arose by mutation from the group of P. triticina genotypes in the simple sequence repeat group NA-5 (4) that have intermediate IT of ;2^- to ;2⁺ to the Thatcher line with Lr21. P. triticina isolates with virulence to Lr21 are a new threat to wheat production since in 2010 more than 50% of the hard red spring wheat acreage in Minnesota and North Dakota relied on Lr21 for effective resistance to leaf rust. References: (1) J. A. Anderson et al. J. Plant Regist. 3:175, 2009. (2) J. A. Kolmer et al. Plant Dis. 94:775, 2010. (3) B. McCallum and P. Seto-Goh. Can. J. Plant Pathol. 32:387, 2010. (4) M. E. Ordoñez and J. A. Kolmer. Phytopathology 99:750, 2009.

Mapping QTL in the porcine MHC region affecting fatness and growth traits in a Meishan/Large White composite population

A number of studies have mapped QTL regulating porcine fatness and growth traits to the region of the major histocompatibility complex (MHC) on porcine chromosome 7 using various experimental crosses. The QTL results from crosses using the Chinese Meishan (MS) (slow growing and fat) are particularly interesting because the MS alleles have been found to be associated with increased growth rate and reduced backfat depth. We investigated these QTL further in a composite population derived previously over eight generations by intercrossing Meishan and the European Large White breeds. Genotype information from 32 markers in a 15cM target region was used in linkage and association analyses. A two-step variance component analysis identified QTL for three growth-related traits, explaining 19 ∼ 24% of the phenotypic variance with a confidence interval of 4 cM in the target region. SNP association analyses found that ss181128966 and ss181128924 within the QTL interval were strongly associated with the growth traits. Only weak signals for an effect on backfat depth were found in the association and linkage analyses, possibly because of past directional selection in the composite population.

Design of polymer nanocomposites in solution by polymer functionalization

Polymer nanocomposites, materials combining polymers and inorganic components such as nanosized crystallites or nanoparticles have attracted significant attention in recent years. A successful strategy for designing polymer nanocomposites is polymer functionalization via attaching functional groups with specific affinity for the inorganic component. In this paper, a systematic investigation by molecular dynamics of polymer functionalization for design of composites combining nanosize crystallites with multiblock polymers in solution is presented. It is shown that functionalization is an example of active self-assembly, where the resulting polymer nanocomposite exhibits a different type of order than the original pure polymer system (without inorganic components). Optimal polymer architectures and concentrations are identified appropriate for different applications, alongside an in-depth analysis on the origin and stability of the resulting phases as well as its experimental implications.

Upregulation of the apelin-APJ pathway promotes neointima formation in the carotid ligation model in mouse

AIMS

To investigate apelin-APJ (angiotensin receptor-like 1) signalling in vascular remodelling, we have examined the pathophysiological response to carotid ligation in apelin knockout mice.

METHODS AND RESULTS

Apelin null animals compared with wild-type mice had significantly decreased neointimal lesion area (1.17 +/- 0.17 vs. 3.33 +/- 1.04 x 10(4) microm(2), P < 0.05) and intima/media ratio (0.81 +/- 0.23 vs. 1.49 +/- 0.44, P < 0.05), averaged over four sites 0.5-2 mm from the ligation. Exogenous apelin infusion rescued the apelin-KO phenotype, promoting neointima formation in the null animals. Apelin null animals showed decreased smooth muscle positive area in the neointima (82.3 +/- 2.4 vs. 63.9 +/- 8.4, P < 0.05), and a smaller percentage BrdU positive cells in the neointima and media (11.06 +/- 1.00 vs. 6.53 +/- 0.86, P < 0.05). Apelin mRNA expression increased initially (5.2-fold, P < 0.01) followed by increased apelin receptor expression (10.1-fold, P < 0.05) in the ligated artery. Cytochemistry studies localized apelin expression to luminal endothelial cells and apelin receptor upregulation to smooth muscle cells (SMC) in the media and neointima. In vitro experiments with cultured rat aortic SMC revealed that apelin stimulation increased migration. In contrast to the increased expression of apelin and apelin receptor in carotid remodelling, expression was not upregulated in the apoE high fat model, and correlated with the known disease-inhibitory effect in this model.

CONCLUSION

These data suggest that increased apelin receptor expression by SMC provides a paracrine pathway in injured vessels that allows endothelial-derived apelin to stimulate their division and migration into the neointima.

Pneumonia risk in COPD patients receiving inhaled corticosteroids alone or in combination: TORCH study results

Inhaled corticosteroids (ICS) are important in reducing exacerbation frequency associated with chronic obstructive pulmonary disease (COPD). However, little is known about the risk of associated infections. In a post hoc analysis of the TOwards a Revolution in COPD Health (TORCH) study, we analysed and identified potential risk factors for adverse event reports of pneumonia in this randomised, double-blind trial comparing twice-daily inhaled salmeterol (SAL) 50 microg, fluticasone propionate (FP) 500 microg, and the combination (SFC) with placebo in 6,184 patients with moderate-to-severe COPD over 3 yrs. Despite a higher withdrawal rate in the placebo arm, after adjusting for time on treatment, a greater rate of pneumonia was reported in the FP and SFC treatment arms (84 and 88 per 1,000 treatment-yrs, respectively) compared with SAL and placebo (52 and 52 per 1,000 treatment-yrs, respectively). Risk factors for pneumonia were age > or =55 yrs, forced expiratory volume in 1 s <50% predicted, COPD exacerbations in the year prior to the study, worse Medical Research Council dyspnoea scores and body mass index <25 kg.m(-2). No increase in pneumonia deaths with SFC was observed; this could not be concluded for FP. Despite the benefits of ICS-containing regimens in COPD management, healthcare providers should remain vigilant regarding the possible development of pneumonia as a complication in COPD patients receiving such therapies.

Adherence to inhaled therapy, mortality and hospital admission in COPD

BACKGROUND

Little is known about adherence to inhaled medication in chronic obstructive pulmonary disease (COPD) and the impact on mortality and morbidity.

METHODS

Data on drug adherence from a randomised double-blind trial comparing inhaled salmeterol 50 microg + fluticasone propionate 500 microg twice daily with placebo and each drug individually in 6112 patients with moderate to severe COPD over 3 years in the TORCH study were used. All-cause mortality and exacerbations leading to hospital admission were primary and secondary end points. The study of adherence was not specified a priori as an ancillary study.

RESULTS

Of the 4880 patients (79.8%) with good adherence defined as >80% use of study medication, 11.3% died compared with 26.4% of the 1232 patients (20.2%) with poor adherence. The annual rates of hospital admission for exacerbations were 0.15 and 0.27, respectively. The association between adherence and mortality remained unchanged and statistically significant after adjusting for other factors related to prognosis (hazard ratio 0.40 (95% CI 0.35 to 0.46), p<0.001). The association was even stronger when analysing on-treatment deaths only. Similarly, the association between adherence and hospital admission remained unchanged and significant in a multivariate analysis (rate ratio 0.58 (95% CI 0.44 to 0.73, p<0.001). The association between increased adherence and improved mortality and reduction in hospital admission was independent of study treatment. The effect of treatment was more pronounced in patients with good adherence than in those with poor adherence.

CONCLUSION

Adherence to inhaled medication is significantly associated with reduced risk of death and admission to hospital due to exacerbations in COPD. Further research is needed to understand these strong associations.

Mutations in LAMB2 causing a severe form of synaptic congenital myasthenic syndrome

Background:

We describe a severe form of congenital myasthenic syndrome (CMS) associated with congenital nephrosis and ocular malformations caused by two truncating mutations in the gene encoding the laminin β2 subunit (LAMB2).

Methods and results:

Mutational analysis in the affected patient, who has a history of a serious untoward reaction to treatment with acetylcholinesterase inhibition, revealed two frame-shifting heteroallelic mutations, a maternally inherited 1478delG and a paternally inherited 4804delC. An anconeus muscle biopsy demonstrated a profound distortion of the architecture and function of the neuromuscular junction, which was strikingly similar to that seen in mice lacking laminin β2 subunit. The findings included: pronounced reduction of the axon terminal size with encasement of the nerve endings by Schwann cells, severe widening of the primary synaptic cleft and invasion of the synaptic space by the processes of Schwann cells, and moderate simplification of postsynaptic folds and intact expression of the endplate acetylcholinesterase. The endplate potential quantal content was notably reduced, while the frequencies and amplitudes of miniature endplate potentials were only moderately diminished and the decay phases of miniature endplate potentials were normal. Western blot analysis of muscle and kidney tissue and immunohistochemistry of kidney tissue showed no laminin β2 expression.

Conclusion:

This case, which represents a new type of synaptic CMS, exemplifies the wide variability of phenotypes associated with LAMB2 mutations and underscores the fundamental role that laminin β2 plays in the development of the human neuromuscular junction.

Micellar crystals in solution from molecular dynamics simulations

Polymers with both soluble and insoluble blocks typically self-assemble into micelles, which are aggregates of a finite number of polymers where the soluble blocks shield the insoluble ones from contact with the solvent. Upon increasing concentration, these micelles often form gels that exhibit crystalline order in many systems. In this paper, we present a study of both the dynamics and the equilibrium properties of micellar crystals of triblock polymers using molecular dynamics simulations. Our results show that equilibration of single micelle degrees of freedom and crystal formation occur by polymer transfer between micelles, a process that is described by transition state theory. Near the disordered (or melting) transition, bcc lattices are favored for all triblocks studied. Lattices with fcc ordering are also found but only at lower kinetic temperatures and for triblocks with short hydrophilic blocks. Our results lead to a number of theoretical considerations and suggest a range of implications to experimental systems with a particular emphasis on Pluronic polymers.

Genetics of Leaf Rust Resistance in Brambling Wheat

The CIMMYT-developed spring wheat 'Brambling' has a high level of adult-plant resistance (APR) to leaf rust caused by Puccinia triticina. Our objectives were to determine the genetic basis of resistance in seedlings and adult plants and the magnitude of genotype × environment effects on the expression of APR. Brambling was crossed with spring wheat 'Jupateco 73S' that is highly susceptible to current predominant P. triticina races in Mexico and the United States. The F₁, F_2:3, F_4:5, F_4:6, and F_5:7 recombinant inbred lines (RILs) were evaluated under artificial field epidemics in Mexico and St. Paul, MN. The RILs also were tested with five races of P. triticina in greenhouse seedling experiments. A DNA marker was used to postulate the presence of slow-rusting gene Lr34 in the RILs. F₁ data suggested strong dominant effect of the APR genes in Brambling. The proportion of homozygous susceptible lines in each generation indicated the presence of three effective resistance genes in adult plants of Brambling in tests in Mexico and three or four genes in tests in St. Paul. The RILs segregated for seedling genes Lr14a and Lr23 and adult-plant slow-rusting gene Lr34 derived from Brambling and Lr17a from Jupateco 73S. Gene Lr23 conditioned APR to P. triticina races present in the St. Paul nursery and accounted for the additional effective gene at this location. Expression of APR was influenced by the environment in the RILs, even though Brambling displayed a consistent response, indicating that stability of APR can be achieved by combinations of slow-rusting resistance genes.

Nanoparticle ordering via functionalized block copolymers in solution

We consider nanoparticles and functionalized copolymers, block copolymers with attached end groups possessing a specific affinity for nanoparticles, in solution. Using molecular dynamics, we show that nanoparticles are able to direct the self-assembly of the polymer/nanoparticle composite. We perform a detailed study for a wide range of nanoparticle sizes and concentrations. We show that the nanoparticles order in a number of distinct phases: simple cubic, layered hexagonal, hexagonal columnar, gyroid, and a novel square columnar. Our results show that nanoparticles ordered with functionalized block copolymers can provide a simple and efficient tool for assembling novel materials with nanometer scale resolution.

Reaction of Elite Wheat Genotypes from the Northern Great Plains of North America to Septoria Diseases

Stagonospora nodorum blotch (SNB), caused by Phaeosphaeria nodorum, and Septoria tritici blotch (STB), caused by Mycosphaerella graminicola, are the main pathogens of the Septoria disease complex of wheat (Triticum aestivum) in North America. This study was conducted to determine the disease reaction of 126 elite hard red spring, white, and durum wheat cultivars and advanced breeding lines collected from the northern Great Plains of the United States and Canada to SNB and STB. Seedlings of the 126 wheat genotypes were evaluated for resistance to SNB and STB under controlled environmental conditions. Moreover, these 126 wheat genotypes also were infiltrated with culture filtrate of P. nodorum isolate Sn2000. Based on disease reactions, three cultivars (McNeal, Dapps, and Oklee) and 12 advanced breeding lines (CA-901-580W, 97SO254-8-1, MN03291, MN03308, WA007925, MT0245, ND756, ND801, ND803, ND808, ND809, and ND811) adapted to the northern Great Plains were found to be resistant to both Septoria diseases and insensitive to the culture filtrate. Additionally, eight genetically diverse lines and cultivars, including two tetraploid wheat genotypes, were identified to be resistant to both Septoria diseases. These results suggest that the wheat genotypes contain a broad genetic base for resistance to the Septoria diseases in the northern Great Plains of the United States and Canada, and the resistant sources identified in this study may be utilized in wheat-breeding programs.

PTHrP increases transcriptional activity of the integrin subunit alpha5

Increasing evidence is emerging highlighting the role of parathyroid hormone-related protein (PTHrP) during metastasis by regulating cell adhesion. The current study demonstrated that modulation of PTHrP expression by PTHrP overexpression and small interfering RNA-induced silencing resulted in changes in cell adhesion and integrin expression. RNA interference of endogenous PTHrP caused a significant reduction in cell adhesion of a breast cancer cell line to collagen type I, fibronectin and laminin (P<0.05) and of a colon cancer cell to collagen type I and fibronectin (P<0.05). Overexpression of PTHrP induced a significant increase in cell adhesion of colon (P<0.0001) and breast (P<0.05) cancer cells to the same extracellular matrix proteins. These PTHrP-mediated effects were attributed to changes in integrin expression as the differences in adhesion profile correlated with the integrin expression profile. In an attempt to elucidate the mechanism whereby PTHrP regulates integrin expression, promoter activity of the integrin α₅ subunit was analysed and significant increases in transcriptional activity were observed in PTHrP overexpressing cells (P<0.0001), which was dependent on nuclear localisation. These results indicate that modulation of cell adhesion is a normal physiological action of PTHrP, mediated by increasing integrin gene transcription.

Bilateral total hip arthroplasty in siblings with Stickler Syndrome

Stickler Syndrome is an infrequent autosomal dominant connective tissue disorder. The most prevalent mutation affects type II collagen gene and results in abnormalities in cartilage, vitreous and nucleus pulposus. Orthopaedic manifestations include joint hyper- mobility and pain with early development of secondary osteoarthritis. The condition has a predilection for the femoral head and patients usually present in their third to fourth decade with secondary hip arthritis. We report on two siblings with Stickler Syndrome who presented with hip osteoarthritis in their third decade of life and underwent staged bilateral total hip arthroplasties (THA). The patients experienced pain relief and improved quality of life after surgery.

Use of a large-scale Triticeae expressed sequence tag resource to reveal gene expression profiles in hexaploid wheat (Triticum aestivum L.)

The US Wheat Genome Project, funded by the National Science Foundation, developed the first large public Triticeae expressed sequence tag (EST) resource. Altogether, 116,272 ESTs were produced, comprising 100,674 5' ESTs and 15 598 3' ESTs. These ESTs were derived from 42 cDNA libraries, which were created from hexaploid bread wheat (Triticum aestivum L.) and its close relatives, including diploid wheat (T. monococcum L. and Aegilops speltoides L.), tetraploid wheat (T. turgidum L.), and rye (Secale cereale L.), using tissues collected from various stages of plant growth and development and under diverse regimes of abiotic and biotic stress treatments. ESTs were assembled into 18,876 contigs and 23,034 singletons, or 41,910 wheat unigenes. Over 90% of the contigs contained fewer than 10 EST members, implying that the ESTs represented a diverse selection of genes and that genes expressed at low and moderate to high levels were well sampled. Statistical methods were used to study the correlation of gene expression patterns, based on the ESTs clustered in the 1536 contigs that contained at least 10 5' EST members and thus representing the most abundant genes expressed in wheat. Analysis further identified genes in wheat that were significantly upregulated (p < 0.05) in tissues under various abiotic stresses when compared with control tissues. Though the function annotation cannot be assigned for many of these genes, it is likely that they play a role associated with the stress response. This study predicted the possible functionality for 4% of total wheat unigenes, which leaves the remaining 96% with their functional roles and expression patterns largely unknown. Nonetheless, the EST data generated in this project provide a diverse and rich source for gene discovery in wheat.

Use of continuous positive airway pressure during spinal anaesthesia in a patient with severe chronic obstructive pulmonary disease

We report the case of a patient with severe chronic obstructive pulmonary disease who underwent local resection of a carcinoma of the rectum under spinal anaesthesia. Although the patient was keen to avoid general anaesthesia and to have the operation under a spinal anaesthetic, pre-operative assessment showed that he could not lie flat. As the surgical procedure required the patient to be in the lithotomy position, ideally with a head-down tilt, it was hoped that continuous positive airway pressure with a facemask during spinal anaesthesia might help him to tolerate the position comfortably. Continuous positive airway pressure at 7.5 cmH(2)O was successfully used to facilitate breathing during surgery under spinal anaesthesia. A combination of regional anaesthesia and continuous positive airway pressure via a facemask is easy to use and may be a useful option in the management of these challenging patients.

Evaluation of Elite Wheat Germ Plasm for Resistance to Tan Spot

Tan spot, caused by Pyrenophora tritici-repentis, is a serious foliar disease of wheat (Triticum aestivum) in North America. Control of tan spot through management practices and fungicide application is possible; however, the use of resistant varieties is the most effective and economical means of controlling tan spot. This study was conducted to determine the disease reaction of 126 elite hard red spring, white, and durum wheat varieties and advanced breeding lines collected from the northern Great Plains of the United States and Canada to individual races/toxins of P. tritici-repentis. Seedling evaluation of the 126 genotypes was done under controlled environmental conditions with virulent races 2, 3, and 5 of P. tritici-repentis and toxins Ptr ToxA and Ptr ToxB. Based on disease reactions, two resistant varieties and two advanced breeding lines adapted to the northern Great Plains were found to be resistant to all the races and insensitive to the toxins tested. Additionally, six genetically diverse lines/varieties were identified to be resistant to tan spot; however, these sources may not be well adapted to the northern Great Plains. These results suggest that the wheat germ plasm contains a broad genetic base for resistance to the most prevalent races of P. tritici-repentis in North America, and the resistant sources identified in this study may be utilized in wheat breeding programs to develop tan spot resistant varieties.