A Mathematical Formalization of Hierarchical Temporal Memory's Spatial Pooler

Hierarchical temporal memory (HTM) is an emerging machine learning algorithm, with the potential to provide a means to perform predictions on spatiotemporal data. The algorithm, inspired by the neocortex, currently does not have a comprehensive mathematical framework. This work brings together all aspects of the spatial pooler (SP), a critical learning component in HTM, under a single unifying framework. The primary learning mechanism is explored, where a maximum likelihood estimator for determining the degree of permanence update is proposed. The boosting mechanisms are studied and found to be only relevant during the initial few iterations of the network. Observations are made relating HTM to well-known algorithms such as competitive learning and attribute bagging. Methods are provided for using the SP for classification as well as dimensionality reduction. Empirical evidence verifies that given the proper parameterizations, the SP may be used for feature learning.Comment: This work was submitted for publication and is currently under review. For associated code, see https://github.com/tehtechguy/mHT

A Mathematical Formalization of Hierarchical Temporal Memory\u27s Spatial Pooler for use in Machine Learning

Hierarchical temporal memory (HTM) is an emerging machine learning algorithm, with the potential to provide a means to perform predictions on spatiotemporal data. The algorithm, inspired by the neocortex, consists of two primary components, namely the spatial pooler (SP) and the temporal memory (TM). The SP is utilized to map similar inputs into generalized sparse distributed representations (SDRs). Those SDRs are then utilized by the TM, which performs sequence learning and prediction. One challenge with HTM is ensuring that proper SDRs are generated from the SP. If the SDRs are not generalizable, the TM will not be able to make proper predictions. This work focuses on the SP and its corresponding output SDRs. A single unifying mathematical framework was created for the SP. The primary learning mechanism was explored, where a maximum likelihood estimator for determining the degree of permanence update was proposed. The boosting mechanisms were studied and found to only be relevant during the initial few iterations of the network. Observations were made relating HTM to well-known algorithms such as competitive learning and attribute bagging. Methods were provided for using the SP for classification as well as dimensionality reduction. Empirical evidence verified that given the proper parameterizations, the SP may be used for feature learning. Similarity metrics were created for scoring the SDRs produced by the SP. The overlap metric proved that the SP is extremely robust to noise. The SP was able to produce similar outputs for a given input, provided the noise did not cause the input to change classes. This overlap metric was further utilized to create a classifier for novelty detection. The SP proved to be able to withstand more noise than the well-known support vector machine (SVM)

The Healthcare Conflict Scale: development, validation and reliability testing of a tool for use across clinical settings

Despite the widespread incidence of conflict and its detrimental impact across a range of health-care settings, there is no validated tool with which to measure it. This paper describes the international innovation of a tool to measure staff-family conflict in pediatrics, intensive care, emergency, palliative care, and nursing homes. Sixty-two health-care workers contributed to focus group discussions to refine a draft tool developed from the literature. Subsequently, 101 health-care workers applied the tool to fictionalized vignettes. The psychometric properties (construct validity, internal consistency, repeatability, and reliability) were explored using principal component analysis, Cronbach’s alpha, and intra-class correlation (ICC) tests. The initial 17-item tool was reduced to seven items within three factors that explained 70.2% of the total variance in overarching construct. The internal consistency of the final overall scale was good (Cronbach’s alpha: 0.750); test–retest reliability of each item was excellent with ICCs ≥0.9. This new tool can be used to identify and score conflict, making it a key reference point in healthcare conflict work across clinical specialties. It's development and testing across specialities and across countries means it can be used in a variety of contexts. The tool provides health-care professionals with a new way to identify and measure conflict, and consequently has the potential to transform health-care relationships across disciplines and settings

Ciprofloxacin resistance in community- and hospital-acquired Escherichia coli urinary tract infections: a systematic review and meta-analysis of observational studies

Background During the last decade the resistance rate of urinary Escherichia coli (E. coli) to fluoroquinolones such as ciprofloxacin has increased. Systematic reviews of studies investigating ciprofloxacin resistance in community- and hospital-acquired E. coli urinary tract infections (UTI) are absent. This study systematically reviewed the literature and where appropriate, meta-analysed studies investigating ciprofloxacin resistance in community- and hospital-acquired E. coli UTIs. Methods Observational studies published between 2004 and 2014 were identified through Medline, PubMed, Embase, Cochrane, Scopus and Cinahl searches. Overall and sub-group pooled estimates of ciprofloxacin resistance were evaluated using DerSimonian-Laird random-effects models. The I2 statistic was calculated to demonstrate the degree of heterogeneity. Risk of bias among included studies was also investigated. Results Of the identified 1134 papers, 53 were eligible for inclusion, providing 54 studies for analysis with one paper presenting both community and hospital studies. Compared to the community setting, resistance to ciprofloxacin was significantly higher in the hospital setting (pooled resistance 0.38, 95 % CI 0.36-0.41 versus 0.27, 95 % CI 0.24-0.31 in community-acquired UTIs, P \u3c 0.001). Resistance significantly varied by region and country with the highest resistance observed in developing countries. Similarly, a significant rise in resistance over time was seen in studies reporting on community-acquired E. coli UTI. Conclusions Ciprofloxacin resistance in E. coli UTI is increasing and the use of this antimicrobial agent as empirical therapy for UTI should be reconsidered. Policy restrictions on ciprofloxacin use should be enhanced especially in developing countries without current regulations

Acute Respiratory and Cardiovascular Outcomes Associated with Low Levels of Ambient Fine Particulate Matter (PM2.5) on the Island of Oahu

Scant literature exists regarding health effects of fine particulate matter (PM2.5) pollution at or below national standards. This study examined the relationship between PM2.5 and acute care use and costs in Honolulu where PM2.5 is low. Single and distributed lag over-dispersed Poisson models were used to examine hospitalizations/emergency department (ED) visits associated with cumulative PM2.5 exposure over the current day and seven previous days (lags 0-7) in 2011. A 10-µg/m3 increase in cumulative PM2.5 concentration was associated with a 32% increase in respiratory admissions (RR=1.32, p=0.001) costing $486,908 and a 24$117,856. Additional research is needed on health effects within pollution lower levels

Five-year antimicrobial resistance patterns of urinary escherichia coli at an Australian tertiary hospital: Time series analyses of prevalence data

This study describes the antimicrobial resistance temporal trends and seasonal variation of Escherichia coli (E. coli) urinary tract infections (UTIs) over five years, from 2009 to 2013, and compares prevalence of resistance in hospital- and community-acquired E. coli UTI. A cross sectional study of E. coli UTIs from patients attending a tertiary referral hospital in Canberra, Australia was undertaken. Time series analysis was performed to illustrate resistance trends. Only the first positive E. coli UTI per patient per year was included in the analysis. A total of 15,022 positive cultures from 8724 patients were identified. Results are based on 5333 first E. coli UTIs, from 4732 patients, of which 84.2% were community-acquired. Five-year hospital and community resistance rates were highest for ampicillin (41.9%) and trimethoprim (20.7%). Resistance was lowest for meropenem (0.0%), nitrofurantoin (2.7%), piperacillin-tazobactam (2.9%) and ciprofloxacin (6.5%). Resistance to amoxycillin-clavulanate, cefazolin, gentamicin and piperacillin-tazobactam were significantly higher in hospital- compared to community-acquired UTIs (9.3% versus 6.2%; 15.4% versus 9.7%; 5.2% versus 3.7% and 5.2% versus 2.5%, respectively). Trend analysis showed significant increases in resistance over five years for amoxycillin-clavulanate, trimethoprim, ciprofloxacin, nitrofurantoin, trimethoprim-sulphamethoxazole, cefazolin, ceftriaxone and gentamicin (P < 0.05, for all) with seasonal pattern observed for trimethoprim resistance (augmented Dickey-Fuller statistic = 4.136; P = 0.006). An association between ciprofloxacin resistance, cefazolin resistance and ceftriaxone resistance with older age was noted. Given the relatively high resistance rates for ampicillin and trimethoprim, these antimicrobials should be reconsidered for empirical treatment of UTIs in this patient population. Our findings have important implications for UTI treatment based on setting of acquisition

Sex differences in in-hospital mortality following a first acute myocardial infarction: Symptomatology, delayed presentation, and hospital setting

Background: Women generally wait longer than men prior to seeking treatment for acute myocardial infarction (AMI). They are more likely to present with atypical symptoms, and are less likely to be admitted to coronary or intensive care units (CCU or ICU) compared to similarly-aged males. Women are more likely to die during hospital admission. Sex differences in the associations of delayed arrival, admitting ward, and mortality have not been thoroughly investigated. Methods: Focusing on presenting symptoms and time of presentation since symptom onset, we evaluated sex differences in in-hospital mortality following a first AMI in 4859 men and women presenting to three emergency departments (ED) from December 2008 to February 2014. Sex-specific risk of mortality associated with admission to either CCU/ICU or medical wards was calculated after adjusting for age, socioeconomic status, triage-assigned urgency of presentation, blood pressure, heart rate, presenting symptoms, timing of presentation since symptom onset, and treatment in the ED. Sex-specific age-adjusted attributable risks were calculated.Results: Compared to males, females waited longer before seeking treatment, presented more often with atypical symptoms, and were less likely to be admitted to CCU or ICU. Age-adjusted mortality in CCU/ICU or medical wards was higher among females (3.1 and 4.9 % respectively in CCU/ICU and medical wards in females compared to 2.6 and 3.2 % in males). However, after adjusting for variation in presenting symptoms, delayed arrival and other risk factors, risk of death was similar between males and females if they were admitted to CCU or ICU. This was in contrast to those admitted to medical wards. Females admitted to medical wards were 89 % more likely to die than their male counterparts. Arriving in the ED within 60 min of onset of symptoms was not associated with in-hospital mortality. Among males, 2.2 % of in-hospital mortality was attributed to being admitted to medical wards rather than CCU or ICU, while for females this age-adjusted attributable risk was 4.1 %. Conclusions: Our study stresses the need to reappraise decision making in patient selection for admission to specialised care units, whilst raising awareness of possible sex-related bias in management of patients diagnosed with an AMI

Five-Year Antimicrobial Resistance Patterns of Urinary Escherichia Coli at an Australian Tertiary Hospital: Time Series Analyses of Prevalence Data

This study describes the antimicrobial resistance temporal trends and seasonal variation of Escherichia coli (E. coli) urinary tract infections (UTIs) over five years, from 2009 to 2013, and compares prevalence of resistance in hospital- and community-acquired E. coli UTI. A cross sectional study of E. coli UTIs from patients attending a tertiary referral hospital in Canberra, Australia was undertaken. Time series analysis was performed to illustrate resistance trends. Only the first positive E. coli UTI per patient per year was included in the analysis. A total of 15,022 positive cultures from 8724 patients were identified. Results are based on 5333 first E. coli UTIs, from 4732 patients, of which 84.2% were community acquired. Five-year hospital and community resistance rates were highest for ampicillin (41.9%) and trimethoprim (20.7%). Resistance was lowest for meropenem (0.0%), nitrofurantoin (2.7%), piperacillin-tazobactam (2.9%) and ciprofloxacin (6.5%). Resistance to amoxycillin-clavulanate, cefazolin, gentamicin and piperacillin-tazobactam were significantly higher in hospital- compared to community-acquired UTIs (9.3% versus 6.2%; 15.4% versus 9.7%; 5.2% versus 3.7% and 5.2% versus 2.5%, respectively). Trend analysis showed significant increases in resistance over five years for amoxycillin-clavulanate, trimethoprim, ciprofloxacin, nitrofurantoin, trimethoprim-sulphamethoxazole, cefazolin, ceftriaxone and gentamicin (

Differences in complete denture longevity and replacement in public and private dental services: A propensity score-matched analysis of subsidised dentures in adult Australians across 20 years

Objectives: To examine the differences in treatment outcomes for patients who received subsidized complete dentures in private dental clinics and in public dental clinics over 20 years in Victoria, Australia.Methods: Between 2000 and 2019, 187 227 complete dentures were provided to eligible public patients by the Victorian public dental system. Of these, approximately 52% were provided to public patients in private clinics through the voucher system. Of the 97 107 participants who received denture care in private clinics, 70 818 were matched 1:1 by propensity score (PS) quantiles with participants who received denture care in public clinics. The PS matching balanced the characteristics between these two groups. Subsequently, a conditional logistic regression model investigated the binary outcome of denture replacement whilst a conditional Poisson regression modelled the number of years to denture replacement. A frailty Cox regression after PS matching investigated denture survival over time.Results: Dentures provided in public clinics had a mean time to replacement of 5.5 years (SD: 34.0) and 25.9% were replaced during the observation period. In the first year of denture service, incidence rate per person year (IR) for complete denture replacement in public clinics was 0.04 (95% CI: 0.04-0.04). Dentures provided in private clinics had a mean time to replacement of 6.5 years (SD: 3.8) with 29.4% replaced during the observation period. In the first year of denture service, the IR for complete denture replacement in private clinics was 0.02 (95% CI: 0.02-0.02), which was less than half that of the public IR. Multivariate analyses found that although private dentures were more likely to be replaced during the observation period than those provided in the public sector (odds ratio [OR]: 1.31, 95% CI: 1.28-1.35, p Conclusions: Increased denture longevity, higher rates of denture replacement and lower rates of early denture replacement were associated with receiving denture care in private clinics as compared with dentures provided in the public sector.</p