2,399 research outputs found
The hidden subgroup problem and quantum computation using group representations
The hidden subgroup problem is the foundation of many quantum algorithms. An efficient solution is known for the problem over abelian groups, employed by both Simon's algorithm and Shor's factoring and discrete log algorithms. The nonabelian case, however, remains open; an efficient solution would give rise to an efficient quantum algorithm for graph isomorphism. We fully analyze a natural generalization of the algorithm for the abelian case to the nonabelian case and show that the algorithm determines the normal core of a hidden subgroup: in particular, normal subgroups can be determined. We show, however, that this immediate generalization of the abelian algorithm does not efficiently solve graph isomorphism
One-sample aggregate data meta-analysis of medians
An aggregate data meta-analysis is a statistical method that pools the
summary statistics of several selected studies to estimate the outcome of
interest. When considering a continuous outcome, typically each study must
report the same measure of the outcome variable and its spread (e.g., the
sample mean and its standard error). However, some studies may instead report
the median along with various measures of spread. Recently, the task of
incorporating medians in meta-analysis has been achieved by estimating the
sample mean and its standard error from each study that reports a median in
order to meta-analyze the means. In this paper, we propose two alternative
approaches to meta-analyze data that instead rely on medians. We systematically
compare these approaches via simulation study to each other and to methods that
transform the study-specific medians and spread into sample means and their
standard errors. We demonstrate that the proposed median-based approaches
perform better than the transformation-based approaches, especially when
applied to skewed data and data with high inter-study variance. In addition,
when meta-analyzing data that consists of medians, we show that the
median-based approaches perform considerably better than or comparably to the
best-case scenario for a transformation approach: conducting a meta-analysis
using the actual sample mean and standard error of the mean of each study.
Finally, we illustrate these approaches in a meta-analysis of patient delay in
tuberculosis diagnosis
Forensic Considerations for the High Efficiency Image File Format (HEIF)
The High Efficiency File Format (HEIF) was adopted by Apple in 2017 as their
favoured means of capturing images from their camera application, with Android
devices such as the Galaxy S10 providing support more recently. The format is
positioned to replace JPEG as the de facto image compression file type, touting
many modern features and better compression ratios over the aging standard.
However, while millions of devices across the world are already able to produce
HEIF files, digital forensics research has not given the format much attention.
As HEIF is a complex container format, much different from traditional still
picture formats, this leaves forensics practitioners exposed to risks of
potentially mishandling evidence. This paper describes the forensically
relevant features of the HEIF format, including those which could be used to
hide data, or cause issues in an investigation, while also providing commentary
on the state of software support for the format. Finally, suggestions for
current best-practice are provided, before discussing the requirements of a
forensically robust HEIF analysis tool.Comment: 8 pages, conference paper pre-prin
Fast Filtering of Known PNG Files Using Early File Features
A common task in digital forensics investigations is to identify known contraband images. This is typically achieved by calculating a cryptographic digest, using hashing algorithms such as SHA256, for each image on a given media, comparing individual digests with a database of known contraband. However, the large capacities of modern storage media, and increased time pressure on forensics examiners, necessitates that more efficient processing mechanisms be developed. This work describes a technique for creating signatures for images of the PNG format which only requires a tiny fraction of the file to effectively distinguish between a large number of images. Highly distinct, and compact, such analysis lays the foundation for future work in fast forensics filtering using subsets of evidential data
Estimating the sample mean and standard deviation from commonly reported quantiles in meta-analysis
Researchers increasingly use meta-analysis to synthesize the results of
several studies in order to estimate a common effect. When the outcome variable
is continuous, standard meta-analytic approaches assume that the primary
studies report the sample mean and standard deviation of the outcome. However,
when the outcome is skewed, authors sometimes summarize the data by reporting
the sample median and one or both of (i) the minimum and maximum values and
(ii) the first and third quartiles, but do not report the mean or standard
deviation. To include these studies in meta-analysis, several methods have been
developed to estimate the sample mean and standard deviation from the reported
summary data. A major limitation of these widely used methods is that they
assume that the outcome distribution is normal, which is unlikely to be tenable
for studies reporting medians. We propose two novel approaches to estimate the
sample mean and standard deviation when data are suspected to be non-normal.
Our simulation results and empirical assessments show that the proposed methods
often perform better than the existing methods when applied to non-normal data
Paediatrics : how to manage scabies
This narrative review addresses scabies, a highly contagious, pruritic infestation of the skin caused by the mite Sarcoptes scabiei var hominis. Scabies is a common disorder that has a prevalence worldwide estimated to be between 200 and 300 million cases per year. Infestation is of greatest concern in children, the elderly, immunocompromised people and resource-poor endemic populations at risk of chronic complications. A diagnosis of scabies involves a clinical suspicion, a detailed targeted history, clinical examination and contact tracing. Dermoscopy and microscopy, where available, is confirmatory. Due to its infectivity and transmissibility, the management for scabies requires a multimodal approach: topical antiscabetic agents are the first line for most cases of childhood classic scabies and their contacts, which must also be identified and treated to prevent treatment failure and reacquisition. Environmental strategies to control fomite-related reinfestation are also recommended. Oral ivermectin, where available, is reserved for use in high-risk cases in children or in mass drug administration programmes in endemic communities. The prevention of downstream complications of scabies includes surveillance, early identification and prompt treatment for secondary bacterial infections, often superficial but can be serious and invasive with associated chronic morbidity and mortality. Postscabetic itch and psychosocial stigma are typical sequelae of the scabies mite infestation. The early identification of patients with scabies and treatment of their contacts reduces community transmission. Although time consuming and labour intensive for caregivers, the implementation of appropriate treatment strategies usually results in prompt cure for the child and their contacts. Here, we provide a summary of treatments and recommendations for the management of paediatric scabies
The importance of benchmarking habitat structure and composition for understanding the extent of fishing impacts in soft sediment ecosystems
Powder Interlayer Bonding of Nickel-Based Superalloys with Dissimilar Chemistries
Novel joining methods are crucial for the aerospace industry to repair components damaged in the high stress, high cycle environment of the jet turbine engine. Powder interlayer bonding (PIB) is a novel joining technique that is being explored for use in the aerospace industry. PIB involves the use of a powder interlayer between two faying surfaces alongside a localised temperature gradient and compressive force to produce one joined workpiece. The use of a localised temperature gradient not only reduces the heat affected zone (HAZ) but also reduces the energy requirements for the process as only a small area of the component needs to be elevated in temperature. Nickel-based superalloys are commonly used in the gas turbine engine due to their superior mechanical properties that are maintained even under the most elevated temperatures experienced in the jet turbine engine. It is therefore essential these alloys can be easily repaired. Conventional joining methods such as friction welding have proved difficult for new generation nickel-based superalloys; therefore, there is much interest in PIB as an alternative repair technology. This study shows the potential of PIB to join dissimilar nickel-based superalloys: bonds with very little porosity were observed after only a short processing time
Using a Smartphone App to Teach Students Practical Epidemiological Skills
Background:
Despite the evidence that shows the pedagogical benefits of experiential education, epidemiology instructors rarely utlize experiential activities to teach epidemiological concepts and skills.
Poster presented at 8th annual 2016 Thomas Jefferson University Faculty Days
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