Recursive n-gram hashing is pairwise independent, at best

Many applications use sequences of n consecutive symbols (n-grams). Hashing these n-grams can be a performance bottleneck. For more speed, recursive hash families compute hash values by updating previous values. We prove that recursive hash families cannot be more than pairwise independent. While hashing by irreducible polynomials is pairwise independent, our implementations either run in time O(n) or use an exponential amount of memory. As a more scalable alternative, we make hashing by cyclic polynomials pairwise independent by ignoring n-1 bits. Experimentally, we show that hashing by cyclic polynomials is is twice as fast as hashing by irreducible polynomials. We also show that randomized Karp-Rabin hash families are not pairwise independent.Comment: See software at https://github.com/lemire/rollinghashcp

RASCAL: DARPA’s Solution to Responsive, Affordable, Micro-Satellite Space Access

RASCAL is a revolutionaryspace access program initiated by the Defense Advanced Research Projects Agency (DARPA). RASCAL will demonstrate the capability to launch microsatellites into low earth orbit routinelyand onshort notice using an air-launch systemarchitecture. A propulsion enhancement – Mass Injection Pre-Compressor Cooling (MIPCC) - allows the air vehicle toobtain high-energyflight conditions and provides the capability for exo-atmospheric staging ofan expendable rocket with satellite payload attached. This architecture effectively reduces recurring launch costs, which are targetedto be $750,000 per launch

An independent audit of the Australian food industry\u27s voluntary front-of-pack nutrition labelling scheme for energy-dense nutrition-poor foods

Background/Objective: Since 2006, the Australian food industry has promoted its front-of-pack (FOP) food labelling system-the Daily Intake Guide (DIG)-as a success story of industry self-regulation. With over 4000 products already voluntary featuring the DIG, the industry argues that government regulation of FOP nutrition labelling is simply unnecessary. However, no independent audit of the industry\u27s self-regulation has ever been undertaken and we present the first such Australian data. Subjects/Methods: Energy-dense nutrient-poor (EDNP) snacks were audited at nine Australian supermarkets, including biscuits, candy, ice creams, chocolates, crisps, sports drinks, energy drinks, flavoured milks, sweetened juices and soft drinks. In these categories nutrition labels were recorded for 728 EDNP products in various packaging sizes. Results: The DIG was displayed on 66% of audited EDNP products but most of these (75%) did not report saturated fat and sugar content. Only generic supermarket EDNP products were likely to display saturated fat and sugar content, compared with very few branded products (48% vs 4%, P\u3c0.001). Branded products not displaying fat and sugar content contained on average 10-times more saturated fat than those displaying such (10% vs 1% DI, P\u3c0.001) and nearly twice as much sugar (21 vs 13% DI, P\u3c0.05). Conclusions: Most Australian manufacturers of EDNP products have adopted the DIG; consistent with industry claims of widespread adoption, but almost all still avoid displaying the high saturated fat and sugar content of their products by opting for the \u27energy alone\u27 option, violating the industry\u27s own voluntarily guidelines and highlighting serious weaknesses with the industry\u27s self-regulation

Novel Crystalline Framework Materials

This t.hesis describes the synthesis and characterisation of metal-organic framework matenals based on cobalt and nickel salts with rigid organic ligands. 'It also contains an account of synthetic and catalytic work towards the incorporation of rhodium into existing frameworks. Chapter 1 provides an introduction to the topic, covering background on the zeolites, an account of the development of frameworks and their applications in modern chemistry, and specific examples relating to the novel frameworks described in later chapters. Chapter 2 covers the synthetic and analytical techniques used to prepare and characterise these materials. ' Chapter 3 describes the detailed crystal structures of five entirely novel frameworks based upon nickel salts and bipyridylligands (4,4'-bipyridine (bipy) and 1,4bis( 4-pyridyl)benzene (3RB». Nickel (II) nitrate and 3RB combine under solvothermal conditions to produce a dense material formed of herringbone layers, [Nb(N03M3RBh] (BC160), with no extra-framework voids. The substitution of nickel nitrate for the equivalent sulphate, combined with room temperature diffusion techniques gives rise to an inclined interpenetrated phase of cross-linked dimer chains, [Nb(S04h(3RBh(H20)] • 2(CH30H) • 3(H20) (BC261). This material displays a 49% extra-framework volume, but suffers from an instability to guest loss. The use of bipy in place of 3RB under similar conditions generates a three-dimensional array of Ni-bipy square grids, pillared by sulphate anions, [Ni(S04)(bipYh] • 3(MeOH) • 3(H20) (BC402). The uniform channels running through the infinite lattice impart an extra-framework volume of 50%. However, given the presence of an irremovable impurity in the as-made crystalline phase, this material presents no opportunities to explore its porous applications. The use of microwave solvothermal techniques produces a new crystalline material, a possible precursor for BC402 above based on the same reactants, [{Ni(bipy)(S04h(H20h} {Ni(bipy)(H20)4} • Bipy] • 3(H20) (BC482). The dense crystal structure comprises two species of one-dimensional chain, which stack in alternating layers along with unbound intercalating bipy molecules. The material possesses no void spaces, and will not undergo phase transition to the BC402 structure. Finally, chiral aspartic acid (Asp) is combined with nickel nitrate and 3RB under solvothermal conditions to form an extended analogue of a bipy-based structure, Nb(L-Asph(3RB)· x(3RB) (BC533_3). Despite a 19% extra-framework volume, this material possesses unbound 3RB occupying its channels. Chapter 4 explores two routes toward catalytic heteronuclear rhodium frameworks. (1) Solvothermal doping of rhodium dimers into CU3(btch(H20h (H3btc = 1,3,5-benzenetricarboxylic acid). Catalytic activity toward the hydrogenation of 1-hexene is investigated, and turnover frequency in the doped frameworks reaches 0.15 molhexane/ mol-Rh/hr. (2) Synthesis of rhodium terephthalate paddlewheel units into existing metal carboxylate frameworks. Discrete paddlewheels are produced, and room temperature and solvothermal techniques toward new heteronuclear frameworks are explored. Chapter 5 covers the synthesis of a further five novel frameworks, based upon a (10,3)-a network topology. New materials are synthesized solvothermally from cobalt nitrate, btc, methyl-pyridines and 1,2-propanediol (1,2-pd) as analogues to existing nickel frameworks, producing four-fold and two-fold interpenetrating nets: C03(btch(4picolineM1,2- pd)6 (BC144) and COJ(btch(3-picoline)&(1,2-pdh (BC143) respectively. Further variations on BC143 are explored through the use of alternative pyridines (resulting in the successful synthesis of Nh(btch(3-ethylpyridine)6(1,2-pdh (BC198» and diols, producing C03(btch(3-picolineM1,2-pentanediolh (BC173) and C03(btch(3picoline) 6(1,2-hexanediolh (BC174). The final two frameworks possess channels functionalised by diol alkyl chains, with a subsequent reduction in void volume

Using eye tracking, time-to-action, heart-rate and perceived task difficulty to assess level of distraction and performance of entry-level paramedicine students in low- versus high-fidelity simulation

Introduction There is limited research investigating the usefulness of high-fidelity simulations (HFS) for early-stage students. Some argue the additional expense of HFS over low-fidelity simulation (LFS) is unnecessary as early-stage students are too easily distracted by non-relevant stimuli inhibiting student’s ability to focus on the core task. However, the extent to which this is true is yet to be empirically tested. Methods First-year paramedicine students were randomly assigned to complete either a LFS or HFS involving a collapsed patient with an obstructed airway. Level of distraction was measured via eye-tracking, arousal via heart-rate (HR), task difficulty via the NASA TLX, and clinical decision making via time-to-action. Student’s perceptions of HFS and LFS were also explored via in-depth interviews immediately following simulations. Results Proportion of time attending to non-relevant stimuli was greater for HFS than LFS students (8.1% vs. 0.9%, ppp=.001). More students from the HFS group revived the patient than the LFS group (58% vs. 30% respectively). Students from the HFS condition achieved time-to-action significantly quicker than those in the LFS condition (p=.010), a trend that remained constant when isolating those removing the obstruction (p\u3c.05). Conclusions Students in HFS suffered from greater distraction, perceived the task as being more difficult and were more aroused than students in LFS. However, HFS students outperformed LFS students with respect to clinical decision making and patient outcomes

Expression of KOC, S100P, mesothelin and MUC1 in pancreatico-biliary adenocarcinomas: development and utility of a potential diagnostic immunohistochemistry panel

<b>Background</b> Pancreatico-biliary adenocarcinomas (PBA) have a poor prognosis. Diagnosis is usually achieved by imaging and/or endoscopy with confirmatory cytology. Cytological interpretation can be difficult especially in the setting of chronic pancreatitis/cholangitis. Immunohistochemistry (IHC) biomarkers could act as an adjunct to cytology to improve the diagnosis. Thus, we performed a meta-analysis and selected KOC, S100P, mesothelin and MUC1 for further validation in PBA resection specimens.<p></p> <b>Methods</b> Tissue microarrays containing tumour and normal cores in a ratio of 3:2, from 99 surgically resected PBA patients, were used for IHC. IHC was performed on an automated platform using antibodies against KOC, S100P, mesothelin and MUC1. Tissue cores were scored for staining intensity and proportion of tissue stained using a Histoscore method (range, 0–300). Sensitivity and specificity for individual biomarkers, as well as biomarker panels, were determined with different cut-offs for positivity and compared by summary receiver operating characteristic (ROC) curve.<p></p> <b>Results</b> The expression of all four biomarkers was high in PBA versus normal ducts, with a mean Histoscore of 150 vs. 0.4 for KOC, 165 vs. 0.3 for S100P, 115 vs. 0.5 for mesothelin and 200 vs. 14 for MUC1 (p < .0001 for all comparisons). Five cut-offs were carefully chosen for sensitivity/specificity analysis. Four of these cut-offs, namely 5%, 10% or 20% positive cells and Histoscore 20 were identified using ROC curve analysis and the fifth cut-off was moderate-strong staining intensity. Using 20% positive cells as a cut-off achieved higher sensitivity/specificity values: KOC 84%/100%; S100P 83%/100%; mesothelin 88%/92%; and MUC1 89%/63%. Analysis of a panel of KOC, S100P and mesothelin achieved 100% sensitivity and 99% specificity if at least 2 biomarkers were positive for 10% cut-off; and 100% sensitivity and specificity for 20% cut-off.<p></p> <b>Conclusion</b> A biomarker panel of KOC, S100P and mesothelin with at least 2 biomarkers positive was found to be an optimum panel with both 10% and 20% cut-offs in resection specimens from patients with PBA.<p></p&gt

Quantification of opportunities for early-stage paramedicine students to practice clinical skills during clinical placements compared with an equal dose of simulation-based workshops

Introduction A reported advantage of simulation-based learning environments (SLE) over clinical placements (CPs) is that the former can provide a greater number and breadth of opportunities to practice level-appropriate clinical skills compared with the random patient presentations provided during the latter. Although logical and widely accepted as fact, we find no published evidence to demonstrate the magnitude, nor indeed veracity, of this assumption. We therefore sought to quantify the clinical skills practiced by entry-level paramedicine students attending a well-selected CP compared with an equal dosage of SLE. Methods N=37 first-year paramedicine students completed activity diaries during 3 days of CP and 3 days of SLE. Opportunities to practice clinical skills were quantified and coded as either: level-appropriate, beyond-level or of non-discipline relevance. Results During SLE, the average student was exposed 226 times to 11 level-appropriate clinical procedures. During CP the average student was exposed 48 times to 24 clinical procedures, the majority relevant to paramedicine (63%), but a minority level-appropriate (38%). Students’ opportunities for supervised, ‘hands on’ practice represented only 10% of exposures in either SLE or CP but in terms of raw numbers of level-appropriate opportunities, SLE provided more than CP (n=23 vs 2). Discussion Our results confirm that SLE provides substantially more opportunities than CP for students to practice level-appropriate skills and is therefore more appropriate for repetitive practice. However, CP is likely to remain useful to students for practicing interpersonal skills and contextualisation of knowledge within the broader health system. Educators should therefore carefully articulate learning objectives before choosing between SLE and CP

Clinical placement before or after simulated learning environments? A naturalistic study of clinical skills acquisition amongst early-stage paramedicine students

Background There is conflicting evidence surrounding the merit of clinical placements (CP) for early-stage health-profession students. Some contend early-stage CPs facilitate contextualisation of subsequently learned theory. Others argue attending CP before attaining skills competency is problematic and should only occur after training in simulated-learning environments (SLE). The evidentiary basis surrounding the extent to which either is true remains limited. Methods First-year paramedicine students (n=85) undertook three days of CP and SLEs as part of course requirements. Students undertook CP either before or after participation in SLEs creating two groups (Clin→Sim/Sim→Clin). Clinical skills acquisition was measured via objectively-structured clinical examinations (OSCE) conducted at four distinct time-points over the semester. Perceptions of difficulty of CP and the SLE were measured via the NASA-TLX. Results Students’ OSCE scores in both groups improved significantly from beginning to end of semester (+35%, pp=.021). Both groups found SLEs more demanding than CP (47.6% vs. 31.4%, pp=.003). Conclusions Differences in temporal demand suggest Clin→Sim students had fewer opportunities to practice clinical skills during CP than Sim→Clin students due to a more limited scope of practice. Sim→Clin students contextualised SLE within subsequent CP resulting in greater improvement in clinical competency by semester’s end in comparison to Clin→Sim students that were forced to contextualise skills retrospectively

X-raying Abell 2125 -- a Large-scale Hierarchical Complex of Galaxies and Hot Gas

We present an 82 ksec Chandra ACIS-I observation of a large-scale hierarchical complex, which consists of various clusters/groups of galaxies and low-surface brightness X-ray emission at z = 0.247. This high-resolution {\sl Chandra} observation allows us for the first time to separate unambiguously the X-ray contributions from discrete sources and large-scale diffuse hot gas. We detect 99 X-ray sources in a $17^\prime \times 17^\prime$ field. Ten of these sources are identified as members of the complex and are mostly radio-bright. Whereas unresolved X-ray sources tend to be associated with galaxies in intermediate density environments, extended X-ray emission peak at bright radio galaxies in the central cluster. In particular, a distinct X-ray trail appears on one side of the fast-moving galaxy C153, clearly due to ram-pressure stripping. The diffuse X-ray emission from the central cluster can be characterized by a thermal plasma with a characteristic temperature of $3.2_{-0.4}^{+0.5}$ keV and a heavy element abundance of $0.24_{-0.12}^{+0.15}$ solar (90% confidence uncertainties). In comparison, a patch of low-surface brightness X-ray emission apparently originates in relatively low density intergalactic gas with a characteristic temperature of $0.98_{-0.27}^{+0.22}$ keV and an abundance of $\lesssim 0.09$ solar. The Chandra observation, together with extensive multi-wavelength data, indicates that the complex represents a projection of several galaxy sub-structures, which may be undergoing major mergers. We discuss the dynamic states of the complex and its sub-structures as well as properties of X-ray-emitting galaxies and the relationship to their environments.Comment: 18 pages plus figures, to be published in ApJ. A complete high resolution version can be found at http://www.astro.umass.edu/~wqd/papers/a2125