A Gradient Descent Algorithm on the Grassman Manifold for Matrix Completion

We consider the problem of reconstructing a low-rank matrix from a small subset of its entries. In this paper, we describe the implementation of an efficient algorithm called OptSpace, based on singular value decomposition followed by local manifold optimization, for solving the low-rank matrix completion problem. It has been shown that if the number of revealed entries is large enough, the output of singular value decomposition gives a good estimate for the original matrix, so that local optimization reconstructs the correct matrix with high probability. We present numerical results which show that this algorithm can reconstruct the low rank matrix exactly from a very small subset of its entries. We further study the robustness of the algorithm with respect to noise, and its performance on actual collaborative filtering datasets.Comment: 26 pages, 15 figure

Obstructive Sleep Apnea and Ischemic Heart Disease

BACKGROUND: IHD is the leading cause of mortality and morbidity in the world. OSA has been established as one of the important modifiable risk factors for IHD. However, it is often undiagnosed and therefore, untreated. Though studies linking IHD and OSA have been published among western populations, there is a paucity of data from India about OSA and IHD. This study aims at identifying the relation between OSA and IHD among a cohort of patients diagnosed with IHD. OBJECTIVES: The main objective was to assess the prevalence of OSA in a population of angiography proven IHD. We also aimed to study the factors affecting severity of OSA. METHODOLOGY: This study was a prospective observational study conducted among 70 patients undergoing evaluation for IHD at the Department of Cardiology, CMC Vellore. Data was collected using a standardized proforma. Subsequently, screening for OSA was performed using a portable screening device, the Apnea Link device. RESULTS: The prevalence of OSA and OSAS among the study cohort was 75.7% and 18.6% respectively. Nearly 50% of patients with OSA had mild OSA. The prevalence of metabolic syndrome and syndrome Z was 77.1% and 58.6% respectively. There was a statistically significant association between severity of OSA and severity of IHD based on coronary angiography and also presence of apneic episodes. Presence of snoring and apneic episodes were found to be important risk factors for development of OSA. CONCLUSION: This study is the first study from South Asia that attempts to study the relation between OSA and IHD in a cohort of patients with IHD. It establishes that OSA is more prevalent among IHD patients as compared to the general population, with a majority of patients having mild OSA. This also reveals the importance of screening for OSA among IHD patients, especially those with a history of snoring and apneic episodes

Energy Efficiency and Alternative Energy Generation in Existing Buildings on a College Campus

Universities and colleges are looking for ways to be sustainable and save energy costs on their campuses. In terms of raw dollars, “America’s colleges and universities spend almost $7 billion a year in energy and utilities”. Campus buildings consume more than 80$20,200 annually. Additionally, these savings also contributed to saving over 281.1 tons of CO2 per year from being emitted into the atmosphere. Validation is an important step in the process to assess if the simulation results are accurate. The simulation results are validated using utility data provided by the Facilities and Services Department for the specific buildings

Physiological and functional characterisation of RafS, a ribosome associated factor of Mycobacteria

Tuberculosis (TB) is a leading cause of death from a single infectious agent and infects one third of the world’s population in a latent form. Latent TB is characterised by presence of TB antigens but a lack of symptoms of TB. Latent TB is associated with the persistent form of Mycobacterium tuberculosis, and is a reservoir from which symptomatic infection arises. Non-replicating persistence (NRP) is postulated to be a reversible state characterised by lack of replication, decreased metabolic activity and increased antimicrobial resistance. To achieve viable persistence, NRP cells have been postulated to require stabilisation of cellular structures needed for stress tolerance and for the transition from NRP to active replication. This study investigates the hypothesis that ribosome stabilisation assists in mycobacterial stress tolerance and persistence. RafS is a novel mycobacterial ribosome associated factor and putative ribosome stabilisation factor. The physiological roles and functional characteristics of RafS are investigated in this study. The role of RafS in M. smegmatis (Msm) and M. tuberculosis (Mtb) physiology were investigated. Competitive survival assays between wild type and ΔrafSMtb illustrated that RafSMtb confers a competitive advantage during survival under nutrient limitation. RafSMsm and RafHMtb were found to significantly inhibit in vitro translation. Furthermore, RafSMsm and RafHMtb inhibited in vitro translation of mRNA with and without Shine Dalgarno sequences. It was determined that RafSMsm is dispensable for growth and survival in several conditions and also for mature biofilm and pellicle formation. Also, RafSMsm is dispensable for tolerance of heat, acid and antibiotic stress. Ribosomal profiling indicated no significant effect of rafSMsm deletion on ribosomal subunit association in log phase and stationary phase rich media cultures. These findings are discussed in the context of mycobacterial growth, survival, stress tolerance and persistence mechanisms.Open Acces

Blood and cerebrospinal fluid biomarkers for Alzheimer’s disease: from clinical to preclinical cohorts

Dementia is a major contributor to global morbidity, mortality and costs associated with health and social care. Alzheimer’s disease (AD) is a common pathology culminating in dementia, but it has a preclinical phase of one to two decades, with early brain deposition of amyloid and tau, followed by synaptic and neuronal degeneration. Early detection during the preclinical phase of AD might enable disease-modifying therapies to be applied during a window of opportunity in which they would be more likely to work. Currently the main biomarkers of AD pathology are neuroimaging markers, which can be costly, or cerebrospinal fluid markers, which require invasive sampling. Blood biomarkers would be relatively less invasive and could be a more cost-effective means for risk stratification, early detection, monitoring progression and measuring response to treatment. The work described here used sensitive assay technology including the Simoa digital immunoassay platform, in large and well-characterised cohorts, to examine candidate blood biomarkers linked to the core AD pathologies of amyloid, tau and neurodegeneration, as specified by the National Institute on Aging and Alzheimer’s Association 2018 research framework. Firstly, experiments on samples from a cognitive clinic cohort established the stability of the blood biomarkers Aβ40, Aβ42, total tau and neurofilament light chain (NFL – a marker of neurodegeneration) to multiple freeze-thaw cycles, and the optimal blood fraction to use for quantifying each of these biomarkers in onward studies. Secondly, an unique large preclinical cohort with life course data (Insight 46, the neuroscience sub-study of 502 individuals from the MRC National Survey of Health and Development; the 1946 British birth cohort) was used to examine the cross-sectional relationships between these blood biomarkers, neuroimaging biomarkers (18F-florbetapir amyloid PET, whole brain and hippocampal volumes, white matter hyperintensity volume and cortical thickness in an AD signature region) and cognitive performance (PACC: preclinical Alzheimer’s composite and its constituents). Through a collaboration with the University of Gothenburg, a novel liquid chromatography-mass spectrometry (LC-MS) method for quantification of plasma amyloid-β species was compared with the commercial Simoa assays in Insight 46. This was the first direct method comparison study of plasma amyloid-β species for the detection of preclinical cerebral amyloid deposition. It showed that the LC-MS method, when combined with age, sex and APOE #-4 carrier status, was able to distinguish PET amyloid status with an optimal (Youden’s cut point) sensitivity of 85.7% and specificity of 72.7%. The Simoa biomarkers of plasma total tau and serum NFL were confirmed to be potentially useful prognostic markers, as lower AD signature cortical thickness was associated with higher plasma total tau and serum NFL, lower whole brain volume was associated with higher plasma total tau, and higher ventricular volume was associated with higher serum NFL. Lower PACC scores were associated with higher serum NFL and lower scores for a paired associative memory test in particular were associated with higher plasma total tau and serum NFL. Thirdly, through a collaboration with Harvard University and the University of California San Diego, a new N-terminal tau biomarker was developed in CSF and plasma that showed good accuracy in distinguishing individuals with symptomatic CSF-defined AD pathology from healthy controls. Taken together, this work has demonstrated the impact of pre-analytical factors on measurements of AD blood biomarkers, validated these biomarkers as indicators of the core pathologies of AD and helped to develop a new tau blood biomarker in AD

Synthesis and fungicidal studies of niobium(V) complexes with N-alkylphenothiazines

Department of Studies in Chemistry, University of Mysore, Mysore-570 006 Manuscript received 31 January 1996, revised 19 August 1996, accepted 18 November 1996 Synthesis and Fungicidal Studies of Niobium(V) Complexes with N-Alkylphenothiazines