Using autoregressive integrated moving average (ARIMA) models to predict and monitor the number of beds occupied during a SARS outbreak in a tertiary hospital in Singapore.

BACKGROUND: The main objective of this study is to apply autoregressive integrated moving average (ARIMA) models to make real-time predictions on the number of beds occupied in Tan Tock Seng Hospital, during the recent SARS outbreak. METHODS: This is a retrospective study design. Hospital admission and occupancy data for isolation beds was collected from Tan Tock Seng hospital for the period 14th March 2003 to 31st May 2003. The main outcome measure was daily number of isolation beds occupied by SARS patients. Among the covariates considered were daily number of people screened, daily number of people admitted (including observation, suspect and probable cases) and days from the most recent significant event discovery. We utilized the following strategy for the analysis. Firstly, we split the outbreak data into two. Data from 14th March to 21st April 2003 was used for model development. We used structural ARIMA models in an attempt to model the number of beds occupied. Estimation is via the maximum likelihood method using the Kalman filter. For the ARIMA model parameters, we considered the simplest parsimonious lowest order model. RESULTS: We found that the ARIMA (1,0,3) model was able to describe and predict the number of beds occupied during the SARS outbreak well. The mean absolute percentage error (MAPE) for the training set and validation set were 5.7% and 8.6% respectively, which we found was reasonable for use in the hospital setting. Furthermore, the model also provided three-day forecasts of the number of beds required. Total number of admissions and probable cases admitted on the previous day were also found to be independent prognostic factors of bed occupancy. CONCLUSION: ARIMA models provide useful tools for administrators and clinicians in planning for real-time bed capacity during an outbreak of an infectious disease such as SARS. The model could well be used in planning for bed-capacity during outbreaks of other infectious diseases as well

Shock Acceleration of Solar Energetic Protons: The First 10 Minutes

Proton acceleration at a parallel coronal shock is modeled with self-consistent Alfven wave excitation and shock transmission. 18 - 50 keV seed protons at 0.1% of plasma proton density are accelerated in 10 minutes to a power-law intensity spectrum rolling over at 300 MeV by a 2500km s-1 shock traveling outward from 3.5 solar radius, for typical coronal conditions and low ambient wave intensities. Interaction of high-energy protons of large pitch-angles with Alfven waves amplified by low-energy protons of small pitch angles is key to rapid acceleration. Shock acceleration is not significantly retarded by sunward streaming protons interacting with downstream waves. There is no significant second-order Fermi acceleration

Unintended and accidental medical radiation exposures in radiology: guidelines on investigation and prevention

This paper sets out guidelines for managing radiation exposure incidents involving patients in diagnostic and interventional radiology. The work is based on collation of experiences from representatives of international and national organizations for radiologists, medical physicists, radiographers, regulators, and equipment manufacturers, derived from an International Atomic Energy Agency Technical Meeting. More serious overexposures can result in skin doses high enough to produce tissue reactions, in interventional procedures and computed tomography, most notably from perfusion studies. A major factor involved has been deficiencies in training of staff in operation of equipment and optimization techniques. The use of checklists and time outs before procedures commence, and dose alerts when critical levels are reached during procedures can provide safeguards to reduce risks of these effects occurring. However, unintended and accidental overexposures resulting in relatively small additional doses can take place in any diagnostic or interventional X-ray procedure and it is important to learn from errors that occur, as these may lead to increased risks of stochastic effects. Such events may involve the wrong examinations, procedural errors, or equipment faults. Guidance is given on prevention, investigation and dose calculation for radiology exposure incidents within healthcare facilities. Responsibilities should be clearly set out in formal policies, and procedures should be in place to ensure that root causes are identified and deficiencies addressed. When an overexposure of a patient or an unintended exposure of a foetus occurs, the foetal, organ, skin and/or effective dose may be estimated from exposure data. When doses are very low, generic values for the examination may be sufficient, but a full assessment of doses to all exposed organs and tissues may sometimes be required. The use of general terminology to describe risks from stochastic effects is recommended rather than calculation of numerical values, as these are misleading when applied to individuals

Ion Anisotropy and High-Energy Variability of Large Solar Particle Events: A Comparative Study

We have made comparative studies of ion anisotropy and high-energy variability of solar energetic particle (SEP) events previously examined by the Solar, Heliospheric, and Interplanetary Environment (SHINE) Workshop campaign. We have found distinctly different characteristics of SEPs between two large "gradual" events having very similar solar progenitors (the 2002 April 21 and August 24 events). Since the scattering centers of SEPs are approximately frozen in the solar wind, we emphasize work in the solar-wind frame where SEPs tend to be isotropized, and small anisotropies are easier to detect. While in the August event no streaming reversal occurred, in the April event the field-aligned anisotropy of all heavy ions showed sign of streaming reversal. The difference in streaming reversal was consistent with the difference in the presence of the outer reflecting boundary. In the April event the magnetic mirror, which was located behind the interplanetary shock driven by the preceding coronal mass ejection (CME), could block the stream of SEPs, while in the August event SEPs escaped freely because of the absence of nearby boundary. The magnetic mirror was formed at the bottleneck of magnetic field lines draped around a flank of the preceding CME. In the previous SHINE event analysis the contrasting event durations and Fe/O ratios of the both events were explained as the interplay between shock geometry and seed population. Our new findings, however, indicate that event duration and time as well as spectral variation are also affected by the presence of a nearby reflecting boundary

Development of LRFD Procedures for Bridge Piles in Iowa—Volume IV: Design Guide and Track Examples

With the goal of producing engineered foundation designs with consistent levels of reliability as well as fulfilling the Federal Highway Administration (FHWA) mandate that all new bridges initiated after October 1, 2007 be designed according to the Load and Resistance Factor Design (LRFD) approach, the Iowa Highway Research Board (IHRB) sponsored three research projects on driven piles (TR-573, -583 and -584). The research outcomes are presented in three reports entitled Development of LRFD Design Procedures for Bridge Piles in Iowa, Volumes I, II, and III, and other research information is available on the project web site at http://srg.cce.iastate.edu/lrfd/. Upon incorporating the regional LRFD recommendations from the completed research into the Iowa DOT Bridge Design Manual (2010) as it is being rewritten under the new title of LRFD Bridge Design Manual (December 2011), and adopting the American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specifications (2010), this Volume IV for driven piles in Iowa was developed. Following the layout of a design guide, the application of the LRFD approach is demonstrated using various pile design examples in three different tracks, which depend on the construction control method used for establishing the pile driving criteria. Piles are designed using the Iowa Blue Book method. The pile driving criteria are established using the Wave Equation Analysis Program (WEAP) in Track 1, the modified Iowa Engineering News Record (ENR) formula in Track 2, and the combination of WEAP and the Pile Driving Analyzer (PDA) with a subsequent pile signal matching analysis using the CAse Pile Wave Analysis Program (CAPWAP) in Track 3. The track examples cover various pile types, three different soil profiles (cohesive, non-cohesive, and mixed) and special design considerations (piles on rock, scouring, downdrag, and uplift)

Test-enhanced learning improves learner attendance during a laparoscopic box trainer simulation program

BACKGROUND: Laparoscopy is the gold standard approach for many surgical procedures, but it is a complex skill to learn. Laparoscopic simulation training may help, but it is unclear how to best engage trainees in these programs. Test‐enhanced learning (TEL) uses regular, well‐defined assessments of performance throughout the training phase of learning. AIM: The aim of this study was to assess the effects of TEL on a laparoscopic simulation program involving a cohort of medical student volunteers. MATERIALS AND METHODS: A prospective cohort study was performed with a convenience sample of 40 medical students. Students were recruited to participate in a ten‐week laparoscopic simulation program. Twenty students participated in a laparoscopic surgical program with TEL (‘TEL group’), and 20 students participated in a standard laparoscopic simulation program (‘control group’). RESULTS: Attendance in the TEL group was significantly higher than in the standard group (71 vs 51.5%, P = 0.03). There was no difference between groups in mean time scores. Four themes were identified in qualitative data drawn from student surveys – personal traits and motivators, training context, clear goals and feedback enabling understanding of one's own performance. CONCLUSION: Testing laparoscopic skills throughout a learning program, in conjunction with individualised feedback and tracking of learning trajectory, increases trainee attendance. Laparoscopic simulation training programs are encouraged to reflect on the pedagogic framework in which their procedural skills training operates

In reply: Response to letter to the editor ‘Predictive Value of NT-proBNP in Patients with Acute Myocardial Infarction’; Regarding Article ‘Trimethylamine N-oxide and Risk Stratification after Acute Myocardial Infarction"

In reply: Response to letter to the editor ‘Predictive Value of NT-proBNP in Patients with Acute Myocardial Infarction’; Regarding Article ‘Trimethylamine N-oxide and Risk Stratification after Acute Myocardial Infarction

Experimental observation of nonlinear Thomson scattering

A century ago, J. J. Thomson showed that the scattering of low-intensity light by electrons was a linear process (i.e., the scattered light frequency was identical to that of the incident light) and that light's magnetic field played no role. Today, with the recent invention of ultra-high-peak-power lasers it is now possible to create a sufficient photon density to study Thomson scattering in the relativistic regime. With increasing light intensity, electrons quiver during the scattering process with increasing velocity, approaching the speed of light when the laser intensity approaches 10^18 W/cm^2. In this limit, the effect of light's magnetic field on electron motion should become comparable to that of its electric field, and the electron mass should increase because of the relativistic correction. Consequently, electrons in such high fields are predicted to quiver nonlinearly, moving in figure-eight patterns, rather than in straight lines, and thus to radiate photons at harmonics of the frequency of the incident laser light, with each harmonic having its own unique angular distribution. In this letter, we report the first ever direct experimental confirmation of these predictions, a topic that has previously been referred to as nonlinear Thomson scattering. Extension of these results to coherent relativistic harmonic generation may eventually lead to novel table-top x-ray sources.Comment: including 4 figure

System Usability Scale Formula as Alternative for Calculating Composite Score of Likert-type Items

Since its conception, Likert Scales have been used extensively in various fields. There are many ways to describe data obtained with Likert scales. In Human Factors research, System Usability Scale (SUS) is a widely adapted Likert Scale instrument to assess the usability of various products and systems. Researchers often have the tendency to modify SUS to fit their context of use, leading to various versions of SUS. Calculation of the composite score for SUS instrument does not involve computation of arithmetic mean/sum and re-coding of statements. SUS formula obtains the score for each Likert-type items and convert them into a single scale range from 0 to 100. Although SUS is a popular instrument, there is no formula introduced to facilitate the calculation of scale. This article aims to introduce a formula to facilitate the calculation of various versions of SUS with different number of items, number of positive and negative statements, as well as scale size. Although primarily meant for SUS practitioners, the formula presented can be used for any instrument adapting Likert-type items should the researchers decide to transform responses into 0-100 scale instead of computation of mean or sum for various statistical analyses. The controversial computation of mean for Likert Scales has been subjected to decades of debate. This article demonstrates an alternate method to calculate composite score of Likert-type items based on calculation of SUS. Results show the formula yield the same results and perfect relationship with mean and sum for various tests, indicating it can be used as an alternative to mean and sum as a composite score of Likert-types items