Error-tolerant oblivious transfer in the noisy-storage model

The noisy-storage model of quantum cryptography allows for information-theoretically secure two-party computation based on the assumption that a cheating user has at most access to an imperfect, noisy quantum memory, whereas the honest users do not need a quantum memory at all. In general, the more noisy the quantum memory of the cheating user, the more secure the implementation of oblivious transfer, which is a primitive that allows universal secure two-party and multi-party computation. For experimental implementations of oblivious transfer, one has to consider that also the devices held by the honest users are lossy and noisy, and error correction needs to be applied to correct these trusted errors. The latter are expected to reduce the security of the protocol, since a cheating user may hide themselves in the trusted noise. Here we leverage entropic uncertainty relations to derive tight bounds on the security of oblivious transfer with a trusted and untrusted noise. In particular, we discuss noisy storage and bounded storage, with independent and correlated noise.Comment: v2: improved presentation, results added on bounded memory and correlated nois

Magnetic resonance relaxation at ultra low temperatures

The focus of this thesis is to produce highly polarised Nuclear Magnetic Resonance (NMR) samples for use in vivo applications. This work focuses on using the brute force method to polarise relevant molecules, for example, 13C labelled pyruvic acid and 13C labelled sodium acetate. The brute force method uses the Boltzmann distribution to polarise a sample by exposing it to large magnetic fields, 15 T, and ultra-low temperatures, ~20 mK. The disadvantage of using this method is the long polarisation time. To counteract the long relaxation times, two sets of relaxation agents were assessed: paramagnetic lanthanides and nanoparticles. Chelated gadolinium is routinely used as a spin-lattice, T1, contrast agent in clinical Magnetic Resonance Imaging (MRI). It is known that when the electron spin flip time is similar to the Larmor frequency, the T1¬ time of the nuclei is reduced. Each lanthanide has a different electron spin flip time, therefore, one lanthanide may be effective at low temperatures. Unfortunately the lanthanides do not prove to be efficient in the millikelvin regime, where the brute force method is at its most effective, so the lanthanides are of limited use. Metals are known to have short T1 times in the millikelvin regime due to the Korringa effect. The conduction electrons of the metal can contribute or absorb energy from nuclei, resulting in a reduction of the T1 of relevant molecules. By having a strong interaction between conduction electrons and the nuclei of interest, it could be possible to reduce the T1¬ of any nuclei of interest. To maximise the contact between the metals and the nuclei, metal nanoparticles were used. Copper and platinum nanoparticle samples are shown to enhance the relaxation rate of nearby protons, however, aluminium and silver nanoparticle samples, which are also expected to be effective, are not. This contradicts the idea that the Korringa effect is the only relaxation mechanism which relaxes the nuclei. The magnetic properties of nanoparticles can be different from their bulk counterpart, therefore, could be contributing to the relaxation of nearby nuclei. It would therefore be advantageous to study the nanoparticle’s magnetisation in a Superconducting Quantum Interference Device (SQUID). Unfortunately, the interpretation of the magnetisation becomes very complicated, as the nanoparticles can react with the solvents. These reactions can result in a 1000-fold increase in the magnetisation of the sample. With the limited magnetic data collected in this work, it is difficult to correlate the nanoparticles magnetic properties with their effectiveness as a T1 relaxation agent

Trends in gabapentinoid prescribing in patients with osteoarthritis: a United Kingdom national cohort study in primary care

Summary Objective To investigate trends in gabapentinoid prescribing in patients with osteoarthritis (OA). Methods Patients aged 40 years and over with a new OA diagnosis recorded between 1995 and 2015 were identified in the Clinical Practice Research Datalink and followed to first prescription of gabapentin or pregabalin, or other censoring event. We estimated the crude and age-standardised annual incidence rates of gabapentinoid prescribing, stratified by patient age, sex, geographical region, and time since OA diagnosis, and the proportion of prescriptions attributable to OA, or to other conditions representing licensed and unlicensed indications for a gabapentinoid prescription. Results Of 383,680 newly diagnosed OA cases, 35,031 were prescribed at least one gabapentinoid. Irrespective of indication, the annual age-standardised incidence rate of first gabapentinoid prescriptions rose from 1.6 (95% CI: 1.3, 2.0) per 1,000 person-years in 2000, to 27.6 (26.7, 28.4) in 2015, a trend seen across all ages and not explained by length of follow-up. Rates were higher among women, younger patients, and in Northern Ireland, Scotland and the North of England. Approximately 9% of first prescriptions could be attributed to OA, a further 13% to comorbid licensed or unlicensed indications. Conclusion Gabapentinoid prescribing in patients with OA increased dramatically between 1995 and 2015. In most cases, diagnostic codes for licensed or unlicensed indications were absent. Gabapentinoid prescribing may be attributable to OA in a significant proportion but evidence for their effectiveness in OA is lacking. Further research to investigate clinical decision making around prescribing these expensive and potentially harmful medicines is recommended

Magnetic resonance relaxation at ultra low temperatures

The focus of this thesis is to produce highly polarised Nuclear Magnetic Resonance (NMR) samples for use in vivo applications. This work focuses on using the brute force method to polarise relevant molecules, for example, 13C labelled pyruvic acid and 13C labelled sodium acetate. The brute force method uses the Boltzmann distribution to polarise a sample by exposing it to large magnetic fields, 15 T, and ultra-low temperatures, ~20 mK. The disadvantage of using this method is the long polarisation time. To counteract the long relaxation times, two sets of relaxation agents were assessed: paramagnetic lanthanides and nanoparticles. Chelated gadolinium is routinely used as a spin-lattice, T1, contrast agent in clinical Magnetic Resonance Imaging (MRI). It is known that when the electron spin flip time is similar to the Larmor frequency, the T1¬ time of the nuclei is reduced. Each lanthanide has a different electron spin flip time, therefore, one lanthanide may be effective at low temperatures. Unfortunately the lanthanides do not prove to be efficient in the millikelvin regime, where the brute force method is at its most effective, so the lanthanides are of limited use. Metals are known to have short T1 times in the millikelvin regime due to the Korringa effect. The conduction electrons of the metal can contribute or absorb energy from nuclei, resulting in a reduction of the T1 of relevant molecules. By having a strong interaction between conduction electrons and the nuclei of interest, it could be possible to reduce the T1¬ of any nuclei of interest. To maximise the contact between the metals and the nuclei, metal nanoparticles were used. Copper and platinum nanoparticle samples are shown to enhance the relaxation rate of nearby protons, however, aluminium and silver nanoparticle samples, which are also expected to be effective, are not. This contradicts the idea that the Korringa effect is the only relaxation mechanism which relaxes the nuclei. The magnetic properties of nanoparticles can be different from their bulk counterpart, therefore, could be contributing to the relaxation of nearby nuclei. It would therefore be advantageous to study the nanoparticle’s magnetisation in a Superconducting Quantum Interference Device (SQUID). Unfortunately, the interpretation of the magnetisation becomes very complicated, as the nanoparticles can react with the solvents. These reactions can result in a 1000-fold increase in the magnetisation of the sample. With the limited magnetic data collected in this work, it is difficult to correlate the nanoparticles magnetic properties with their effectiveness as a T1 relaxation agent

Clinical recognition of symptomatic midfoot osteoarthritis: findings from the clinical assessment study of the foot

Purpose: Osteoarthritis (OA) is a common yet poorly understood cause of disabling foot pain. In the absence of radiographic confirmation of OA, clinical diagnosis in primary care is inhibited by lack of evidence informing clinical examination. This study aimed to determine whether the presence of symptomatic midfoot OA (SMOA) can be clinically identified in older adults with midfoot pain presenting to primary care.Methods: A diagnostic model using brief clinical assessments was developed using cross-sectional data from 274 adults aged ≥50 years who had self-reported midfoot pain in the last month and attended a research assessment clinic between 2010-2011. All clinical assessment data were collected by trained physiotherapy or podiatry assessors adhering to a standardised, quality-controlled protocol. Presence of radiographic midfoot OA in at least one of four scored joints (1st and 2nd cuneo-metatarsal joint, navicular-first cuneiform joint, and talo-navicular joint) was ascertained by a single reader using a validated atlas and scoring system, and who was blinded to the clinical assessment data. Radiographic OA was defined as a score of ≥2 for osteophytes or joint space narrowing on either weight-bearing dorso-plantar or lateral views. SMOA was defined as co-occuring radiographic OA and midfoot pain. One foot per participant was entered into the analysis. The selection of predictor variables was based on known associations with OA or mechanically-driven putative links to SMOA. Significant predictor variables (p<0.25 from likelihood ratio tests) from univariable analyses were simultaneously entered into a multivariable logistic regression model and backward elimination (p=0.05) was performed. The Hosmer-Lemeshow statistic assessed the calibration of the refitted model and the area under the curve (AUC) evaluated discrimination. Histograms visually summarised discrimination. Internal validation of the model was performed using 1000 bias-corrected bootstrap samples with replacement.Results: 274 participants without inflammatory disease comprised 125 men and 149 women (mean age 65 yrs, SD 9). Of these 155 had midfoot pain and 119 had SMOA. 16 univariable analyses identified 9 significant predictors and no collinearity was observed. In addition to force-entered variables (age, gender, body mass index (BMI)), only two independent predictors of SMOA were retained in the multivariable analysis: (i) reduced ankle dorsiflexion with the knee flexed and (ii) absence of a midfoot exostosis. Based on the strength of univariable association, the Foot Posture Index, subtalar inversion and ankle dorsiflexion with the knee extended appeared too weak to contribute to the final model, whereas the removal of the Arch Index and foot length-corrected navicular height was due to the stronger influence of age explaining these relationships. The final fitted model was well calibrated (p=0.79) but discrimination was poor (AUC, 0.69; 95%CI: 0.62, 0.75). Bootstrapping revealed a small degree of overfitting. The use of categorical predictor variables in continuous form did not identify any other predictors, nor did it improve model performance.Conclusions: Brief clinical assessments offer only marginal improvement to age, gender and BMI for identifying SMOA. Milder severity in a population sample, random and systematic error in the clinical assessment, and variable expression of SMOA disease manifestation may have contributed to poor diagnostic accuracy. A clinically defined SMOA phenotype based on modifiable joint loading characteristics may offer an alternative approach to facilitating the development of more targeted biomechanical interventions

Sexual behaviour, sexually transmitted infections and attitudes to chlamydia testing among a unique national sample of young Australians: Baseline data from a randomised controlled trial

Background: Chlamydia infection is the most common notifiable sexually transmitted infection (STI) in Australia and mostly affects young people (15 - 25 years). This paper presents baseline data from a randomised controlled trial that aimed to increase chlamydia testing among sexually active young people. The objectives were to identify associations between sexual behaviour, substance use and STI history and explore attitudes to chlamydia testing. Methods: This study was conducted in cyberspace. Study recruitment, allocation, delivery of interventions and baseline and follow up data collection all took place online. Participants were 16 - 25 years old and resided in Australia. Substance use correlates of sexual activity; predictors of history of STIs; barriers to and facilitators of chlamydia testing were analysed. Results: Of 856 participants (79.1% female), 704 had experienced penetrative intercourse. Sexually active participants were more likely to smoke regularly or daily, to drink alcohol, or to have binge drunk or used marijuana or other illicit substances recently. Risk factors for having a history of any STI were 3 or more sexual partners ever, 6 or more partners in the past 12 months, condom non-use and being 20 years or older. Almost all sexually active participants said that they would have a chlamydia test if their doctor recommended it. Conclusions: Sexually active young people are at risk of STIs and may engage in substance use risk behaviours. Where one health risk behaviour is identified, it is important to seek information about others. Chlamydia testing can be facilitated by doctors and nurses recommending it. Primary care providers have a useful role in chlamydia control. © 2014 Kang et al.; licensee BioMed Central Ltd

Tissue-specific expression of a human Polymorphic Epithelial mucin (MUCI) in transgenic mice

The human MUC1 gene codes for the core protein of a mucin which is expressed by glandular epithelia and the carcinomas which develop from these tissues. The core protein is aberrantly glycosylated in cancers, and some antibodies show specificity in their reactions with the cancer-associated mucin, which also contains epitopes recognized by T-cells from breast and pancreatic cancer patients. For evaluating the potential use of mucin-reactive antibodies and mucin-based immunogens in cancer patients, a mouse model, expressing the MUC1 gene product PEM (polymorphic epithelial mucin) as a self antigen, would be extremely useful. To this end, we have developed transgenic mouse strains expressing the human MUC1 gene product in a tissue-specific manner. The TG4 mouse strain was established using a 40-kilobase fragment containing 4.5 kilobases of 5\u27 and 27 kilobases of 3\u27 flanking sequence. The TG18 strain was developed using a 10.6-kilobase SacII fragment from the 40-kilobase fragment; this fragment contained 1.6 kilobases of 5\u27 sequence and 1.9 kilobases of 3\u27 flanking sequence. Both strains showed tissue specificity of expression of the MUC1 gene, which was very similar to the profile of expression seen in human tissues. The antibody SM-3 is directed to a core protein epitope, which is selectively exposed in breast cancers and which shows a more restricted distribution on normal human tissues. It was established that the distribution of the SM-3 epitope of PEM in the tissues of the transgenic mice is similar to that seen in humans. The transgenic mouse strains described here should form the basis for the development of a preclinical model for the evaluation of PEM-based antigens and of antibodies directed to PEM in cancer therapy

The structure of the hexameric atrazine chlorohydrolase AtzA

Atrazine chlorohydrolase (AtzA) was discovered and purified in the early 1990s from soil that had been exposed to the widely used herbicide atrazine. It was subsequently found that this enzyme catalyzes the first and necessary step in the breakdown of atrazine by the soil organism Pseudomonas sp. strain ADP. Although it has taken 20 years, a crystal structure of the full hexameric form of AtzA has now been obtained. AtzA is less well adapted to its physiological role (i.e. atrazine dechlorination) than the alternative metal-dependent atrazine chlorohydrolase (TrzN), with a substrate-binding pocket that is under considerable strain and for which the substrate is a poor fit

Rotation and activity of pre-main-sequence stars

We present a study of rotation (vsini) and chromospheric activity (Halpha EW) based on an extensive set of high-resolution optical spectra obtained with MIKE on the 6.5m Magellan Clay telescope. Our targets are 74 F-M dwarfs in the young stellar associations Eta Cha, TW Hydrae, Beta Pic, and Tuc-Hor, spanning ages from 6 to 30 Myr. While the Halpha EW for most F and G stars are consistent with pure photospheric absorption, most K and M stars show chromospheric emission. By comparing Halpha EW in our sample to results in the literature, we see a clear evolutionary sequence: Chromospheric activity declines steadily from the T Tauri phase to the main sequence. Using activity as an age indicator, we find a plausible age range for the Tuc-Hor association of 10-40 Myr. Between 5 and 30 Myr, we do not see evidence for rotational braking in the total sample, thus angular momentum is conserved, in contrast to younger stars. This difference indicates a change in the rotational regulation at 5-10 Myr, possibly because disk braking cannot operate longer than typical disk lifetimes, allowing the objects to spin up. The rotation-activity relation is flat in our sample; in contrast to main-sequence stars, there is no linear correlation for slow rotators. We argue that this is because young stars generate their magnetic fields in a fundamentally different way from main-sequence stars, and not just the result of a saturated solar-type dynamo. By comparing our rotational velocities with published rotation periods for a subset of stars, we determine ages of 13 (7-20) Myr and 9 (7-17} Myr for the Eta Cha and TWA associations, respectively, consistent with previous estimates. Thus we conclude that stellar radii from evolutionary models by Baraffe et al. (1998) are in agreement with the observed radii within +-15%. (abridged)Comment: 40 pages, 8 figures, ApJ, in pres