Fire Hazards of Refrigerants in Air Conditioning Control System

Air conditioning control systems are commonly installed in restaurants, commercial buildings, office buildings and institutional buildings in Hong Kong. The systems invariably involve the use of fans for moving the air, filters for cleansing, ducts for air distribution, a control system for regulating the amount of heating or cooling automatically and a refrigerating plant connected to the heat exchange surface. The ducts in turn present the possibility of spreading fire and smoke throughout the building or areas served. According to the local Code of Practice for Minimum Fire Service Installations and Equipment [1], when a ventilation or air conditioning control system to a building is provided, it shall stop mechanically induced air movement within a designated fire compartment. In order to fulfil such requirement, the architects and building services engineers will design to install associated equipment of air conditioning control systems to satisfy the relevant fire safety requirements of the local authority, which includes the provision of fire resisting ducting, fire dampers, smoke detectors and fire resisting cables, etc. However, lessons learned from past experience reveal that owners or property management staff of the buildings or covered areas and maintenance contractors will mainly concern the efficiency and energy saving of the systems without paying much attention to the fire hazards arising from the use of refrigerants. It is also noted that fire or explosion incidents [2] involving air conditioning control systems are often attributed to improper maintenance work conducted by maintenance contractors, such as refilling the refrigerating plant with poor quality refrigerants, recharging refrigerants incompatible with the metal parts of the system, refilling refrigerants at high pressure resulting in bursting of piping and joints, valves contaminated by grease, presence of an ignition source in close proximity of the refrigerating plant, etc. In general, refrigerants present two basic hazards [3], namely toxicity and flammability. Refrigerants mix readily with air and if flammable, may reach flammable concentrations ready to be ignited by an ignition source. As diffusion may not take place rapidly enough to avoid the hazards in the event of leakage, fire or explosion may occur. With reference to a recent fire with explosion incident involving air conditioning control system in a restaurant in Hong Kong, this paper will outline and discuss the fire hazards of refrigerants in air conditioning control systems

Telling stories in the use of portfolio assessment in higher education: some implementation issues

Evidence has shown that the results of traditional standardized tests characterized by pencil and paper formats, multiple-choice responses and time-restricted completion are not sufficient in telling how pupils engage in the learning process and their progress in learning. In addition, these tests tend to emphasize on the assessment of basic skills but fail to measure higher level thinking and problem solving skills. This inadequacy can be addressed by incorporating authentic assessment approaches such as performance tasks, portfolios, and grading for team effort. This paper aims to tell stories from an action learning research group whose members have used ‘portfolio’ as an alternative assessment strategy in higher education

Reliability and Validity of the Monitored Functional Task Evaluation (MFTE) for Patients with Chronic Obstructive Pulmonary Disease (COPD)

This article describes the development of a new functional measure — the Monitored Functional Task Evaluation (MFTE) — a symptom-limited evaluation that is used to measure the functional performance of an individual with chronic obstructive pulmonary disease (COPD), and to document a client's physiological changes through repeated testing. Stage I of the study included developing the content validity of the instrument. Stage II consisted of establishing the performance profile, test-retest and inter-rater reliability using a convenience sample of 27 inpatients and outpatients who had COPD. In stage III, the criterion-related and discriminative validity of the instrument was verified in a retrospective sample of 124 inpatients and day patients who had COPD. Results indicated that there was high intra- and inter-rater reliability for the total score of MFTE. Significant correlation of the MFTE was found with parameters such as Moser's Activities of Daily Living (ADL) class, COPD disability class, 6-minute walking distance, work capacity in terms the ratio of the metabolic rate associated with a given activity to the resting metabolic rate, and the fatigue dimension of the Chronic Respiratory Disease Questionnaire. In addition, prediction of group membership to Moser's ADL class revealed that 52.4% of the original grouped cases could be correctly classified by the MFTE alone. In conclusion, the MFTE is a useful measure to evaluate functional performance as well as document physiological changes in patients with moderate-to-severe COPD from both conceptual and empirical perspectives

Predicting high-risk patients using the International IGA Nephropathy risk prediction tool: a preliminary single-centre analysis

Introduction The International IgA Nephropathy Risk Prediction Tool (IgAN- RPT) has been utilized to predict renal progression up to 5 or 7 years after biopsy via histological and clinical risk factors. We reported the preliminary analysis of the renal outcome of IgAN patients in relation to their predicted risk based on the IgAN-RPT at biopsy. Methods We included 29 biopsy-proven adult IgAN patients diagnosed between 2010 and 2017. The IgAN-RPT predicted risk score at 5 years was calculated for each patient. The primary outcome was the risk of developing a 50% decline in the estimated glomerular filtration rate (eGFR) or end stage renal disease (ESRD) at 5 years after biopsy. Independent Student T-test and chi-square analysis were used to compare the clinical data between groups, while Kaplan-Meier survival analysis was done to compare the predicted and observed outcomes within risk groups using SPSS 26 (2020; IBM Corp., Armonk, NY, USA). Results Our cohort consisted of 13 Chinese, 12 Malay and 4 Indian patients with a mean eGFR of 68.2 (±5.7) at biopsy. The median 5-year IgAN-RPT risk score was 13.12% (IQR: 6.02 to 28.00). 20.7% (n=6) reached the primary outcome. Statistically significant; lower mean serum albumin level [30.5 ± 3.3 versus 38.0 ± 6.9, t=2.571 (27), p= 0.016], higher proportion of not using RAS blocker [100.0% versus 11.5%, χ2 = 10.9 (2), p=0.004] and higher proportion of using immunosuppression at biopsy [36.4% versus 5.9%, χ2 =7.54 (2), p=0.023] were noted among these patients. At this preliminary point, none of the other clinical data was significant, thus no further multivariate analyses were performed. To compare the predicted and observed outcomes within the risk group, a cut-off point of 30% for the predicted risk was determined by calculating the Youden Index of a receiving operating curve plotted between the predicted outcome versus observed outcome at 5 years. Results showed well-separated curves between the two risk groups, indicating a good discriminant ability of the tool among our patients. Conclusions Our study demonstrated the median 5-year 1gAN-RPT risk score among our patients was 13.12% with 20.7% of them reaching the primary outcome. Moreover, a cut-off of 30% IgAN- RPT predicted score could discriminate between high-risk versus low-risk patients to develop ESRD or a 50% decline in eGFR in this population. No conflict of interes

Stochastic Acceleration by Turbulence

The subject of this paper is stochastic acceleration by plasma turbulence, a process akin to the original model proposed by Fermi. We review the relative merits of different acceleration models, in particular the so called first order Fermi acceleration by shocks and second order Fermi by stochastic processes, and point out that plasma waves or turbulence play an important role in all mechanisms of acceleration. Thus, stochastic acceleration by turbulence is active in most situations. We also show that it is the most efficient mechanism of acceleration of relatively cool non relativistic thermal background plasma particles. In addition, it can preferentially accelerate electrons relative to protons as is needed in many astrophysical radiating sources, where usually there are no indications of presence of shocks. We also point out that a hybrid acceleration mechanism consisting of initial acceleration by turbulence of background particles followed by a second stage acceleration by a shock has many attractive features. It is demonstrated that the above scenarios can account for many signatures of the accelerated electrons, protons and other ions, in particular $^3$He and $^4$He, seen directly as Solar Energetic Particles and through the radiation they produce in solar flares.Comment: 29 pages 7 figures for proceedings of ISSI-Bern workshop on Particle Acceleration 201

Measurement of jet suppression in central Pb-Pb collisions at root s(NN)=2.76 TeV

The transverse momentum(p(T)) spectrum and nuclear modification factor (R-AA) of reconstructed jets in 0-10% and 10-30% central Pb-Pb collisions at root s(NN) = 2.76 TeV were measured. Jets were reconstructed using the anti-k(T) jet algorithm with a resolution parameter of R = 0.2 from charged and neutral particles, utilizing the ALICE tracking detectors and Electromagnetic Calorimeter (EMCal). The jet p(T) spectra are reported in the pseudorapidity interval of \eta(jet)\ 5 GeV/c to suppress jets constructed from the combinatorial background in Pb-Pb collisions. The leading charged particle requirement applied to jet spectra both in pp and Pb-Pb collisions had a negligible effect on the R-AA. The nuclear modification factor R-AA was found to be 0.28 +/- 0.04 in 0-10% and 0.35 +/- 0.04 in 10-30% collisions, independent of p(T), jet within the uncertainties of the measurement. The observed suppression is in fair agreement with expectations from two model calculations with different approaches to jet quenching. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V.Peer reviewe

Searches for lepton-flavour-violating decays of the Higgs boson in s=13\sqrt{s}=13 TeV pp\mathit{pp} collisions with the ATLAS detector

This Letter presents direct searches for lepton flavour violation in Higgs boson decays, H → eτ and H → μτ , performed with the ATLAS detector at the LHC. The searches are based on a data sample of proton–proton collisions at a centre-of-mass energy √s = 13 TeV, corresponding to an integrated luminosity of 36.1 fb−1. No significant excess is observed above the expected background from Standard Model processes. The observed (median expected) 95% confidence-level upper limits on the leptonflavour-violating branching ratios are 0.47% (0.34+0.13−0.10%) and 0.28% (0.37+0.14−0.10%) for H → eτ and H → μτ , respectively.publishedVersio

Combination of searches for Higgs boson pairs in pp collisions at \sqrts = 13 TeV with the ATLAS detector

This letter presents a combination of searches for Higgs boson pair production using up to 36.1 fb(-1) of proton-proton collision data at a centre-of-mass energy root s = 13 TeV recorded with the ATLAS detector at the LHC. The combination is performed using six analyses searching for Higgs boson pairs decaying into the b (b) over barb (b) over bar, b (b) over barW(+)W(-), b (b) over bar tau(+)tau(-), W+W-W+W-, b (b) over bar gamma gamma and W+W-gamma gamma final states. Results are presented for non-resonant and resonant Higgs boson pair production modes. No statistically significant excess in data above the Standard Model predictions is found. The combined observed (expected) limit at 95% confidence level on the non-resonant Higgs boson pair production cross-section is 6.9 (10) times the predicted Standard Model cross-section. Limits are also set on the ratio (kappa(lambda)) of the Higgs boson self-coupling to its Standard Model value. This ratio is constrained at 95% confidence level in observation (expectation) to -5.0 &lt; kappa(lambda) &lt; 12.0 (-5.8 &lt; kappa(lambda) &lt; 12.0). In addition, limits are set on the production of narrow scalar resonances and spin-2 Kaluza-Klein Randall-Sundrum gravitons. Exclusion regions are also provided in the parameter space of the habemus Minimal Supersymmetric Standard Model and the Electroweak Singlet Model. For complete list of authors see http://dx.doi.org/10.1016/j.physletb.2019.135103</p

Search for flavour-changing neutral currents in processes with one top quark and a photon using 81 fb⁻¹ of pp collisions at \sqrts = 13 TeV with the ATLAS experiment

A search for flavour-changing neutral current (FCNC) events via the coupling of a top quark, a photon, and an up or charm quark is presented using 81 fb−1 of proton–proton collision data taken at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Events with a photon, an electron or muon, a b-tagged jet, and missing transverse momentum are selected. A neural network based on kinematic variables differentiates between events from signal and background processes. The data are consistent with the background-only hypothesis, and limits are set on the strength of the tqγ coupling in an effective field theory. These are also interpreted as 95% CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tuγ coupling of 36 fb (78 fb) and on the branching ratio for t→γu of 2.8×10−5 (6.1×10−5). In addition, they are interpreted as 95% CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tcγ coupling of 40 fb (33 fb) and on the branching ratio for t→γc of 22×10−5 (18×10−5). © 2019 The Author(s

Comparison between simulated and observed LHC beam backgrounds in the ATLAS experiment at Ebeam =4 TeV

Results of dedicated Monte Carlo simulations of beam-induced background (BIB) in the ATLAS experiment at the Large Hadron Collider (LHC) are presented and compared with data recorded in 2012. During normal physics operation this background arises mainly from scattering of the 4 TeV protons on residual gas in the beam pipe. Methods of reconstructing the BIB signals in the ATLAS detector, developed and implemented in the simulation chain based on the \textscFluka Monte Carlo simulation package, are described. The interaction rates are determined from the residual gas pressure distribution in the LHC ring in order to set an absolute scale on the predicted rates of BIB so that they can be compared quantitatively with data. Through these comparisons the origins of the BIB leading to different observables in the ATLAS detectors are analysed. The level of agreement between simulation results and BIB measurements by ATLAS in 2012 demonstrates that a good understanding of the origin of BIB has been reached