bluuebunny/crossref_metadata_2025 huggingface dataset:
Part 1: Pressure ulcer assessment – the development of Critical Care Pressure Ulcer Assessment Tool made Easy (CALCULATE)
Authors: Richardson Annette , Barrow Isabel
Published: March 2015

Introduction

Critically ill patients are at high risk of developing pressure ulcers resulting in serious untoward patient and health care system outcomes. Pressure ulcer prevention is therefore an important patient safety priority and establishing a structured approach to pressure ulcer risk assessment to identify patients at risk is a critical first step.

Methods

The literature was searched using three electronic databases from 2000 to 2011 to identify papers reporting on pressure ulcer risk factors and assessment in adult critical care. The review and appraisal of papers were conducted by two critical care nurses. Papers underwent detailed review if they met inclusion criteria where they identified pressure ulcer assessment scores, scales or risk factors and related to adult critical care patients

Findings

Seven papers were reviewed. No single assessment tool was sufficiently validated for critically ill patients and seven key critical care risk factors were identified. These risk factors were: mechanical ventilation, impaired circulation, dialysis, long surgery, low protein and too unstable to turn.

Tool development

The tool Critical Care Pressure Ulcer Assessment Tool made Easy (CALCULATE) was developed utilizing the risk factors from the literature and expert critical care nursing consensus decision‐making.

Discussion

In the absence of current consensus, valid assessment scales and limited evidence for the most appropriate pressure ulcer assessment for critically ill patients, this assessment tool offers an easy, appropriate alternative for critically ill patients than existing tools primarily validated for acute care wards.

Conclusions

‘CALCULATE’ offers an important contribution towards the advancement and development of critical care pressure ulcer risk assessment. Future research is needed to further enhance and inform pressure ulcer risk assessment of the critically ill patients.

Implications for practice

The identification of critical care risk factors may be an indicative method of assessing pressure ulcer risk in the critically ill patients.
Optimizing treatments for anxiety by age and genetics
Authors: Casey B.J. , Lee Francis S.
Published: March 2015

This paper highlights recent human neuroimaging and cross‐species developmental and genetic studies that examine how fear regulation varies by age and the individual, especially during the period of adolescence, when there is a peak in the prevalence of anxiety disorders. The findings have significant implications for understanding who may be at risk for anxiety disorders and for whom, and when, an exposure‐based therapy may be most effective. We provide proof of concept for targeting treatment to the individual as a function of age and genetics, inferred from mouse and human studies, and suggest optimization of treatment for nonresponders.
Long‐Term Results of Cardiac Resynchronization Therapy: A Comparison between CRT‐Pacemakers versus Primary Prophylactic CRT‐Defibrillators
Authors: REITAN CHRISTIAN , CHAUDHRY UZMA , BAKOS ZOLTAN , BRANDT JOHAN , WANG LINGWEI , PLATONOV PYOTR G. , BORGQUIST RASMUS
Published: March 2015

Background

Cardiac resynchronization therapy (CRT) with or without a defibrillator has a positive effect on mortality and morbidity for patients with heart failure. However, comparisons between CRT‐defibrillators (CRT‐D) and CRT‐pacemakers (CRT‐P) are relatively scarce outside the clinical trial setting. This study aimed to assess baseline characteristics in relation to long‐term prognosis in patients treated with CRT, and to investigate the potential benefit of CRT‐D versus CRT‐P.

Methods

Data were retrospectively collected from the medical records of all consecutive patients treated with CRT‐P or primary prophylactic CRT‐D at a large tertiary care center between 1999 and 2012. Predictors of mortality were investigated, and time‐dependent analysis was performed with all‐cause mortality as the primary end point.

Results

A total of 705 patients were included (69.6 ± 10 years, 78% New York Heart Association classes III–IV, left ventricular ejection fraction median 25%, 16% female, 36% CRT‐D). The patients were followed for a median of 59 months. Annual mortality differed between CRT‐D primary prophylactic and CRT‐P groups (5.3% and 11.8%, respectively), but when adjusted for covariates, CRT‐D treatment (compared to CRT‐P) was not associated with better long‐term survival. Independent predictors of survival were: age, use of loop diuretics, hemoglobin levels, and use of renin angiotensin aldosterone system blockers.

Conclusions

In CRT treatment outside of the clinical trial setting, CRT‐D treatment was not an independent predictor of long‐term survival. Future research should focus on correct selection of the patients who receive enough benefit of an added defibrillator to justify CRT‐D implantation instead of CRT‐P treatment only.
Catheter Ablation of Atrial Fibrillation Using Zero‐Fluoroscopy Technique: A Randomized Trial
Authors: BULAVA ALAN , HANIS JIRI , EISENBERGER MARTIN
Published: March 2015

Background

Recent advances in 3D mapping systems, such as simultaneous visualization of multiple catheters and contact force measurement, have allowed a significant reduction in fluoroscopic times during radiofrequency (RF) ablation (RFA) procedures. The objective was to investigate whether RFA of paroxysmal atrial fibrillation (PAF) using the CARTO 3 system (Biosense Webster, Diamond Bar, CA, USA) and intracardiac echocardiography (ICE) can be performed safely without fluoroscopy.

Methods and Results

Eighty patients with PAF were randomized in a 1:1 ratio to undergo either fluoroscopically guided pulmonary vein isolation (PVI) (X+) or PVI without fluoroscopy (X−). In the X− fluoroscopy group, catheter placement, transseptal puncture, left atrial geometry reconstruction, and PVI were accomplished solely using ICE imaging and CARTO mapping. The total procedure duration and RF application time in both the X− and X+ groups were comparable (92.5 ± 22.9 minutes vs 99.9 ± 15.9 minutes, P = 0.11 and 1785 ± 548 seconds vs 1755 ± 450 seconds, P = 0.79, respectively). Zero fluoroscopic time was achieved in all patients in the X− group with the exception of one patient, where 8 seconds of fluoroscopy was needed to assess proper position of the guide‐wire in the femoral vein. No serious procedure‐related complications were recorded and no differences in arrhythmia‐free survival at 12 months were found between the groups.

Conclusion

RFA using ICE imaging and the CARTO 3 mapping system with contact force measurement is capable of eliminating fluoroscopy in patients undergoing PVI. Exclusion of fluoroscopic imaging does not seem to compromise patient safety and does not affect overall procedure duration, RF application time, or mid‐term efficacy.
Lumbar Lipomeningomyelocele Associated with Multiple Café au Lait Spots: A Case Report
Authors: Balasubramanian Pradeep , Srinivas C. R. , Arunachalam Pavai , Thirumurthy K. S. , Rajkumar P. R. , Manuvidhya H.
Published: March 2015

We report on a child with several café au lait spots in association with a lumbar lipomeningomyelocele as an apparently new association. Cutaneous markers, the identification of which plays a crucial role in the early diagnosis and management of spinal malformations, can accompany occult spinal dysraphism. Herein we report a case of lumbar lipomeningomyelocele associated with an overlying café au lait spot that served as a marker of occult spinal dysraphism. The patient also had segmental café au lait spots on the face, making the association unique.
Bacterial Colonization of Thrombosed Dialysis Arteriovenous Grafts
Authors: Beathard Gerald A.
Published: March 2015

In the absence of obvious infection, an abandoned arteriovenous graft (AVG) is generally left in place. This has been thought to be the best solution in view of the surgical procedure that would be required for its removal. However, there are reports of occult infection in these retained AVGs that can lead to significant infectious complications. In addition, there is evidence that abandoned, retained AVGs may contribute to the inflammatory state that exist in association with dialysis patients. This observational report of 100 cases of thrombosed AVG in which the thrombus was cultured at the time of thrombectomy demonstrated a significant degree of bacterial colonization in these cases without evidence of bacteremia. It is proposed that this could be the mechanism by which occult infection in an abandoned, retained AVGs occurs.
Scripted secure base knowledge and its relation to perceived social acceptance and competence in early middle childhood
Authors: Psouni Elia , Di Folco Simona , Zavattini Giulio Cesare
Published: March 2015

Attachment theory regards experiences with caregivers as the affective ground for the development of early images of self, possibly embedded in scripted secure‐base knowledge as a rudimentary representation of early caregiver‐child attachment relationships. However, the possible link between implicit representations of secure base availability – and the image of self in these representations – and explicit evaluations of self, is still unclear. The present study assessed whether implicit knowledge of secure‐base interactions with caregivers is related to self‐reported self‐esteem in early middle childhood (N = 97 second‐grade children). Results revealed that children with rich knowledge of secure base interactions perceived themselves not only as more accepted and appreciated by their peers and mothers but also as more cognitively competent, beyond actual differences in cognitive competence. Yet, given the limited strength of this link, the role of contextual factors beyond attachment ought to be considered in the assessment of self‐perception in early middle childhood.
Inter‐individual differences in HLA expression can impact the CDC crossmatch
Authors: Hönger G. , Krähenbühl N. , Dimeloe S. , Stern M. , Schaub S. , Hess C.
Published: March 2015

How human leucocyte antigen (HLA) expression levels on human lymphocytes relate to clinically relevant in vitro cytotoxicity testing has not been defined. Here, cross‐sectional (n = 14) and longitudinal (n = 6) semi‐quantitative assessment of HLA expression on lymphocytes was performed. Complement‐dependent cytotoxicity (CDC) and cellular allo‐reactivity were assessed vis‐à‐vis target cells with defined levels of HLA expression. On CD4+ and CD8+ T‐cells, and on B‐cells, intra‐individual HLA levels varied ≤1.5‐fold, whereas inter‐individual HLA expression varied 2.34‐fold and 2.07‐fold on CD4+ and CD8+ T‐cells, respectively, and 2.90‐fold on B‐cells. Importantly, CDC crossmatch reactions induced by anti‐HLA‐A2 monoclonal antibody as well as patient sera solely containing HLA‐A2 antibodies were significantly impacted by HLA‐A2 expression levels on donor cells. Likewise, cytotoxicity of HLA‐A2 reactive effector cells was induced proportionate to availability of HLA‐A2. These data demonstrate that human HLA expression on lymphocytes from healthy blood donors is fairly stable intra‐individually, yet varies significantly from person to person. Variability in HLA expression levels can impact functional cytotoxic reactions in vitro, including the widely used CDC crossmatch assay. Prospective studies are required to test the clinical relevance of this finding.
A molecular mechanism that confines the activity pattern of miR165 in Arabidopsis leaf primordia
Authors: Tatematsu Kiyoshi , Toyokura Koichi , Miyashima Shunsuke , Nakajima Keiji , Okada Kiyotaka
Published: March 2015

In Arabidopsis leaf primordia, the expression of HD‐Zip III, which promotes tissue differentiation on the adaxial side of the leaf primordia, is repressed by miRNA165/166 (miR165/166). Small RNAs, including miRNAs, can move from cell to cell. In this study, HD‐Zip III expression was strikingly repressed by miR165/166 in the epidermis and parenchyma cells on the abaxial side of the leaf primordia compared with those on the adaxial side. We also found that the MIR165A locus, which was expressed in the abaxial epidermis, was sufficient to establish the rigid repression pattern of HD‐Zip III expression in the leaf primordia. Ectopic expression analyses of MIR165A showed that the abaxial‐biased miR165 activity in the leaf primordia was formed neither by a polarized distribution of factors affecting miR165 activity nor by a physical boundary inhibiting the cell‐to‐cell movement of miRNA between the adaxial and abaxial sides. We revealed that cis‐acting factors, including the promoter, backbone, and mature miRNA sequence of MIR165A, are necessary for the abaxial‐biased activity of miR165 in the leaf primordia. We also found that the abaxial‐determining genes YABBYs are trans‐acting factors that are necessary for the miR165 activity pattern, resulting in the rigid determination of the adaxial–abaxial boundary in leaf primordia. Thus, we proposed a molecular mechanism in which the abaxial‐biased patterning of miR165 activity is confined.
Instability in Nonlinear Oscillation of Dielectric Elastomers
Authors: Zhu Jian
Published: March 2015

A membrane of a dielectric elastomer oscillates when subject to AC voltage. Its oscillation is nonlinear due to large deformation and nonlinear electromechanical coupling. Dynamic instability in dielectric elastomers—the oscillation with an unbounded amplitude—is investigated in this paper. The critical amplitude of AC voltage for dynamic instability varies with the frequency of AC voltage and reaches a valley when the superharmonic, harmonic, or subharmonic resonance is excited. Prestretches can improve dielectric elastomer actuators' capabilities to resist dynamic instability. The critical deformation at the onset of dynamic instability can be much larger than that at the onset of static instability. Oscillation of dielectric elastomers can be used for applications, such as vibration shakers for haptic feedback, soft loudspeakers, soft motors, and soft pumps. We hope that the current analyses can improve the understanding of dynamic behavior of dielectric elastomers and enhance their stability and reliability.
Problem Map: An Ontological Framework for a Computational Study of Problem Formulation in Engineering Design
Authors: Dinar Mahmoud , Danielescu Andreea , MacLellan Christopher , Shah Jami J. , Langley Pat
Published: March 2015

Studies of design cognition often face two challenges. One is a lack of formal cognitive models of design processes that have the appropriate granularity: fine enough to distinguish differences among individuals and coarse enough to detect patterns of similar actions. The other is the inadequacies in automating the recourse-intensive analyses of data collected from large samples of designers. To overcome these barriers, we have developed the problem map (P-maps) ontological framework. It can be used to explain design thinking through changes in state models that are represented in terms of requirements, functions, artifacts, behaviors, and issues. The different ways these entities can be combined, in addition to disjunctive relations and hierarchies, support detailed modeling and analysis of design problem formulation. A node–link representation of P-maps enables one to visualize how a designer formulates a problem or to compare how different designers formulate the same problem. Descriptive statistics and time series of entities provide more detailed comparisons. Answer set programming (ASP), a predicate logic formalism, is used to formalize and trace strategies that designers adopt. Data mining techniques (association rule and sequence mining) are used to search for patterns among large number of designers. Potential uses of P-maps are computer-assisted collection of large data sets for design research, development of a test for the problem formulation skill, and a tutoring system.
Task-Oriented Adaptive Maintenance Support System
Authors: Huang Ying , Wang Xingjun , Gardoni Mickaël , Coulibaly Amadou
Published: March 2015

Technical manuals for complex systems like automobiles, airplanes, and machine tools, often consist of a huge amount of documentation containing disassembling, assembling instructions and drawings of parts, subassemblies, and exploded views. So it is difficult for users to find a piece of information they need amongst these huge amount of documentations. In order to support maintenance implementation process effectively, a task-oriented adaptive maintenance support (TOAMS) system is designed to provide an intelligent, adaptive electronic support for maintaining complex equipment according to user profiles and their work in hand. By building user model, task model, and product model, document model is configured by multiview and some pieces of semantic information are added into data modules. An agent based software application is being developed to support and allow a systematic utilization of the “adaptive response” by integrating it into the daily work of the technician. An application is presented to show the applicability of our method.
Effect of Cyclic Heat, Humidity, and Joining Method on the Static and Dynamic Performance of Lightweight Multimaterial Single-Lap Joints
Authors: Nassar Sayed A. , Sakai Kaori
Published: March 2015

This experimental study investigates the effect of environmental loading and joining methods on the static and dynamic performance of lightweight multimaterial single-lap joints (SLJ). Joint adherend material combinations are divided into two groups; namely, composite-based and steel-based materials that include glass fiber reinforced polymer (GFRP), steel (St), aluminum (Al), and magnesium (Mg). A commercially available adhesive is selected for the study. Investigated joining methods include bonding-only, bolting-only, and hybrid bonding-and-bolting. Static performance is assessed by the load transfer capacity (LTC) of SLJ after they have been subjected to heat cycling at ambient level of relative humidity, or after heat cycling at high relative humidity. Dynamic performance is measured by durability life (in cycles) of SLJ test samples under a fixed dynamic load ratio in a tensile–tensile fatigue test, after they have been subjected to heat cycling and humidity. The cyclic test load fluctuated between 67.5% and 75% of the static LTC at ambient condition. Sample finding includes the significant effect of heat cycling at an ambient humidity level; it has tripled the LTC of bonded-only composite-to-composite SLJ, relative to their baseline LTC at ambient conditions. Detailed discussion of the results, observations, and conclusions are presented in this paper.
Dynamics of the Planetary Roller Screw Mechanism
Authors: Jones Matthew H. , Velinsky Steven A. , Lasky Ty A.
Published: March 2015

This paper develops the dynamic equations of motion for the planetary roller screw mechanism (PRSM) accounting for the screw, rollers, and nut bodies. First, the linear and angular velocities and accelerations of the components are derived. Then, their angular momentums are presented. Next, the slip velocities at the contacts are derived in order to determine the direction of the forces of friction. The equations of motion are derived through the use of Lagrange's Method with viscous friction. The steady-state angular velocities and screw/roller slip velocities are also derived. An example demonstrates the magnitude of the slip velocity of the PRSM as a function of both the screw lead and the screw and nut contact angles. By allowing full dynamic simulation, the developed analysis can be used for much improved PRSM system design.
Dynamic Identification of Thermodynamic Parameters for Turbocharger Compressor Models
Authors: Burke R. D. , Olmeda P. , Serrano J. R.
Published: March 2015

A novel experimental procedure is presented which allows simultaneous identification of heat and work transfer parameters for turbocharger compressor models. The method introduces a thermally transient condition and uses temperature measurements to extract the adiabatic efficiency and internal convective heat transfer coefficient simultaneously, thus capturing the aerodynamic and thermal performance. The procedure has been implemented both in simulation and experimentally on a typical turbocharger gas stand facility. Under ideal conditions, the new identification predicted adiabatic efficiency to within 1% point1 and heat transfer coefficient to within 1%. A sensitivity study subsequently showed that the method is particularly sensitive to the assumptions of heat transfer distribution pre- and postcompression. If 20% of the internal area of the compressor housing is exposed to the low pressure intake gas, and this is not correctly assumed in the identification process, errors of 7–15% points were observed for compressor efficiency. This distribution in heat transfer also affected the accuracy of heat transfer coefficient which increased to 20%. Thermocouple sensors affect the transient temperature measurements and in order to maintain efficiency errors below 1%, probes with diameter of less than 1.5 mm should be used. Experimentally, the method was shown to reduce the adiabatic efficiency error at 90 krpm and 110 krpm compared to industry-standard approach from 6% to 3%. However at low speeds, where temperature differences during the identification are small, the method showed much larger errors.
Fundamental Explorations of Spring-Varied, Free Piston Linear Engine Devices
Authors: Robinson Matthew C. , Clark Nigel N.
Published: March 2015

The conventional crank-based internal combustion engine faces many challenges to remain a viable option for electric power generation. Limitations in mechanical, thermal, and combustion efficiencies must be overcome by innovations in existing technologies and progress toward new ones. The free piston linear engine (FPLE) has the potential to meet these challenges. Friction losses are reduced by avoiding rotational motion and linkages. Instead, electrical power is generated by the oscillation of the translator through a stator. Naturally, variable compression ratio provides a unique platform to employ advanced combustion regimes. However, possibly high variations in stroke length result in unknown dead center piston positions and greater difficulties in compression control as compared to conventional engines. Without control, adverse occurrences such as misfire, stall, over-fueling, and rapid load changes pose greater complications for stable system operation. Based on previous research, it is believed that incorporating springs will advance former designs by both increasing system frequency and providing a restoring force to improve cycle-to-cycle stability. Despite growing interest in the FPLE, current literature does not address the use of springs within a dual, opposed piston design. This investigation is an extension of recent efforts in the fundamental analysis of such a device. Previous work by the authors combined the dynamics of a damped, spring mass system with in-cylinder thermodynamic expressions to produce a closed-form nondimensional model. Simulations of this model were used to describe ideal Otto cycle as the equilibrium operating point. The present work demonstrates more realistic modeling of the device in three distinct areas. In the previous model, the work term was a constant coefficient over the length of the stroke, instantaneous heat addition (representing combustion) was only seen at top dead center (TDC) positions, and the use of the Otto cycle included no mechanism for heat transfer except at dead center positions. Instead, a position based sinusoid is employed for the work coefficient causing changes to the velocity and acceleration profiles. Instantaneous heat addition prior to TDC is allowed causing the compression ratio to decrease toward stable, Otto operation, and a simple heat transfer scheme is used to permit cylinder gas heat exchange throughout the stroke resulting in deviation from Otto operation. Regardless, simulations show that natural system stability arises under the right conditions. Highest efficiencies are achieved at a high compression ratio with minimal heat transfer and near-TDC combustion.
Parametric Study of Injection Rates With Solenoid Injectors in an Injection Quantity and Rate Measuring Device
Authors: Busch Stephen , Miles Paul C.
Published: March 2015

A Moehwald HDA (HDA is a German acronym: Hydraulischer Druckanstieg: hydraulic pressure increase) injection quantity and rate measuring unit is used to investigate injection rates obtained with a fast-acting, preproduction diesel solenoid injector. Experimental parametric variations are performed to determine their impact on measured injection rate traces. A pilot–main injection strategy is investigated for various dwell times; these preproduction injectors can operate with very short dwell times with distinct pilot and main injection events. Dwell influences the main injection rate shape. A comparison between a diesel-like fuel and a gasoline-like fuel shows that injection rates are comparable for a single injection but dramatically different for multiple injections with short dwells.
Impact of Very High Injection Pressure on Soot Emissions of Medium Speed Large Diesel Engines
Authors: Engelmayer Michael , Wimmer Andreas , Taucher Gert , Hirschl Gernot , Kammerdiener Thomas
Published: March 2015

Measures exist to adjust tailpipe NOx emissions to assigned values, for example cooled exhaust gas recirculation (EGR) or a selective catalytic reduction (SCR) catalyst in conjunction with urea. The situation is quite different with soot when use of a trap is not feasible for reasons of cost, space requirements and maintenance. Due to the highly complex soot formation and oxidation process, soot emissions cannot be targeted as easily as NOx. So, how can soot be kept within the limits? In principle, soot can be controlled by allocating sufficient oxygen and establishing good mixing conditions with vaporized fuel. The most effective measures target the injection system, e.g., increasing injection pressure, applying multiple injections, optimizing nozzle geometry. To investigate the impact of very high injection pressure on soot, an advanced injection system with rail pressure capability up to 3000 bar and a Bosch injector was installed at the Large Engines Competence Center (LEC) in Graz. Full load and part load operating points at constant speed and in accordance with the propeller law were investigated at the test bed to quantify the impact of high injection pressure on soot emissions. Test runs were conducted with both SCR and EGR while varying injection timing and air–fuel ratios. Use of a statistical method, design of experiments (DOE), helped reduce the number of tests. Optical investigations of the spray and combustion were conducted. The goal was to obtain soot concentration history traces with the two color method in order to better understand how soot originates and to be able to calibrate 3D CFD (computational fluid dynamics) FIRE spray models for use with injection pressures of up to 3000 bar. Very low soot emissions can be achieved using high pressure injection, even when EGR is applied. DOE results provide a clear picture of the relationships between the parameters and can be used to optimize set values for the whole speed and load range. A reliable spray break up model can be used in further 3D CFD simulation to investigate how to reduce soot emissions.
Effect of Particle Size Distribution on the Deep-Bed Capture Efficiency of an Exhaust Particulate Filter
Authors: Viswanathan Sandeep , Rothamer David , Sakai Stephen , Hageman Mitchell , Foster David , Fansler Todd , Andrie Michael
Published: March 2015

The exhaust filtration analysis system (EFA) developed at the University of Wisconsin–Madison was used to perform microscale filtration experiments on cordierite filter samples using particulate matter (PM) generated by a spark ignition direct injection (SIDI) engine fueled with gasoline. A scanning mobility particle sizer (SMPS) was used to characterize running conditions with four distinct particle size distributions (PSDs). The distributions selected differed in the relative number of accumulation versus nucleation mode particles. The SMPS and an engine exhaust particle sizer (EEPS) were used to simultaneously measure the PSD downstream of the EFA and the real-time particulate emissions from the SIDI engine to determine the evolution of filtration efficiency (FE) during filter loading. Cordierite filter samples with properties representative of diesel particulate filters (DPFs) were loaded with PM from the different engine operating conditions. The results were compared to understand the impact of PSD on filtration performance as well as the role of accumulation mode particles on the diffusion capture of PM. The most penetrating particle size (MPPS) was observed to decrease as a result of particle deposition within the filter substrate. In the absence of a soot cake, the penetration of particles smaller than 70 nm was seen to gradually increase with time, potentially due to increased velocities in the filter as flow area reduces during filter loading, or due to decreasing wall area for capture of particles by diffusion. Particle re-entrainment was not observed for any of the operating conditions.
Hole trap distribution on 2 MeV electron irradiated high-k dielectrics
Authors: Dueñas Salvador , Castán Helena , García Héctor , Fuentes Lisa María , Bailón Luis , Campabadal Francesca , Rafí Joan Marc , González Mireia Bargalló , Takakura Kenitirou , Tsunoda Isao , Yoneoka Masashi
Published: March 2015

The effects of 2 MeV electron irradiation on the electrical properties of high-k dielectric based metal–insulator–semiconductor capacitors have been studied. Samples consist of 5.9 nm-thick films of aluminum oxide and hafnium oxide deposited by atomic layer deposition on silicon substrates. Deep-level transient spectroscopy (DLTS) and admittance measurements reveal that electron irradiation modifies the defect density of both surface states at the dielectric–semiconductor interface and border traps existing inside the dielectric. The experimental results indicate that irradiation has a double effect. The incident electrons transfer their energy and generate additional surface states, leading to a degradation of the interface. On the other hand, irradiation generates electron–hole pairs inside the dielectric. Some of the holes are trapped by border traps located inside the dielectric at locations close to the interface. As a result, border traps capturing holes are neutralized and become inactive after irradiation. Moreover, interface state profiles, as measured by DLTS, are affected by the presence of border traps and yield overestimated interface state densities. Admittance spectroscopy is used to distinguish among border traps and interface traps. A detailed study of the conductance signal as a function of voltage, temperature and frequency for samples with different irradiation doses (nonirradiated, 2.5, 25, and 250 Mrad) is presented here. The influence of the irradiation dose has been analyzed in order to compare the defect distribution before and after irradiation.
Using Rose's metal alloy as a pinhole collimator material in preclinical small‐animal imaging: A Monte Carlo evaluation
Authors: Peterson Mikael , Strand Sven‐Erik , Ljungberg Michael
Published: March 2015

Purpose:

Pinhole collimation is the most common method of high‐resolution preclinical single photon emission computed tomography imaging. The collimators are usually constructed from dense materials with high atomic numbers, such as gold and platinum, which are expensive and not always flexible in the fabrication step. In this work, the authors have investigated the properties of a fusible alloy called Rose's metal and its potential in pinhole preclinical imaging. When compared to current standard pinhole materials such as gold and platinum, Rose's metal has a lower density and a relatively low effective atomic number. However, it is inexpensive, has a low melting point, and does not contract when solidifying. Once cast, the piece can be machined with high precision. The aim of this study was to evaluate the imaging properties for Rose's metal and compare them with those of standard materials.

Methods:

After validating their Monte Carlo code by comparing its results with published data and the results from analytical calculations, they investigated different pinhole geometries by varying the collimator material, acceptance angle, aperture diameter, and photon incident angle. The penetration‐to‐scatter and penetration‐to‐total component ratios, sensitivity, and the spatial resolution were determined for gold, tungsten, and Rose's metal for two radionuclides, 99Tcm and 125I.

Results:

The Rose's metal pinhole‐imaging simulations show higher penetration/total and scatter/total ratios. For example, the penetration/total is 50% for gold and 75% for Rose's metal when simulating 99Tcm with a 0.3 mm aperture diameter and a 60° acceptance angle. However, the degradation in spatial resolution remained below 10% relative to the spatial resolution for gold for acceptance angles below 40° and aperture diameters larger than 0.5 mm.

Conclusions:

Extra penetration and scatter associated with Rose's metal contribute to degradation in the spatial resolution, but this degradation is not always substantial. The most important factor besides the collimator material was the acceptance angle. This should be kept to a minimum to prevent unnecessary scatter and penetration. For 125I, the difference in spatial resolution between gold and Rose's metal is very small, 2.2% in the worst‐case scenario. Based on these results, the authors conclude that Rose's metal is an alternative to standard materials not only for low‐energy photon imaging but also for medium‐energy applications that require low‐cost, flexible pinhole configurations and designs, and that can tolerate a degraded spatial resolution.
Systematic calibration of an integrated x‐ray and optical tomography system for preclinical radiation research
Authors: Yang Yidong , Wang Ken Kang‐Hsin , Eslami Sohrab , Iordachita Iulian I. , Patterson Michael S. , Wong John W.
Published: March 2015

Purpose:

The cone beam computed tomography (CBCT) guided small animal radiation research platform (SARRP) has been developed for focal tumor irradiation, allowing laboratory researchers to test basic biological hypotheses that can modify radiotherapy outcomes in ways that were not feasible previously. CBCT provides excellent bone to soft tissue contrast, but is incapable of differentiating tumors from surrounding soft tissue. Bioluminescence tomography (BLT), in contrast, allows direct visualization of even subpalpable tumors and quantitative evaluation of tumor response. Integration of BLT with CBCT offers complementary image information, with CBCT delineating anatomic structures and BLT differentiating luminescent tumors. This study is to develop a systematic method to calibrate an integrated CBCT and BLT imaging system which can be adopted onboard the SARRP to guide focal tumor irradiation.

Methods:

The integrated imaging system consists of CBCT, diffuse optical tomography (DOT), and BLT. The anatomy acquired from CBCT and optical properties acquired from DOT serve as a priori information for the subsequent BLT reconstruction. Phantoms were designed and procedures were developed to calibrate the CBCT, DOT/BLT, and the entire integrated system. Geometrical calibration was performed to calibrate the CBCT system. Flat field correction was performed to correct the nonuniform response of the optical imaging system. Absolute emittance calibration was performed to convert the camera readout to the emittance at the phantom or animal surface, which enabled the direct reconstruction of the bioluminescence source strength. Phantom and mouse imaging were performed to validate the calibration.

Results:

All calibration procedures were successfully performed. Both CBCT of a thin wire and a euthanized mouse revealed no spatial artifact, validating the accuracy of the CBCT calibration. The absolute emittance calibration was validated with a 650 nm laser source, resulting in a 3.0% difference between simulated and measured signal. The calibration of the entire system was confirmed through the CBCT and BLT reconstruction of a bioluminescence source placed inside a tissue‐simulating optical phantom. Using a spatial region constraint, the source position was reconstructed with less than 1 mm error and the source strength reconstructed with less than 24% error.

Conclusions:

A practical and systematic method has been developed to calibrate an integrated x‐ray and optical tomography imaging system, including the respective CBCT and optical tomography system calibration and the geometrical calibration of the entire system. The method can be modified and adopted to calibrate CBCT and optical tomography systems that are operated independently or hybrid x‐ray and optical tomography imaging systems.
Characterization and implementation of OSL dosimeters for use in evaluating the efficacy of organ‐based tube current modulation for CT scans of the face and orbits
Authors: Marsh R. M. , Silosky M.
Published: March 2015

Purpose:

The purpose of this work was to characterize commercially available optically stimulated luminescent (OSL) dosimeters for general clinical applications and apply the results to the development of a method to evaluate the efficacy of a vendor‐specific organ‐based tube current modulation application for both phantom and clinical computed tomography (CT) scans of the face and orbits.

Methods:

This study consisted of three components: (1) thorough characterization of the dosimeters for CT scans in phantom, including evaluations of depletion, fading, angular dependence, and conversion from counts to absorbed dose; (2) evaluation of the efficacy of using plastic glasses to position the dosimeters over the eyes in both phantom and clinical studies; and (3) preliminary dosimetry measurements made using organ‐based tube current modulation in computed tomography dose index (CTDI) and anthropomorphic phantom studies.

Results:

(1) Depletion effects were found to have a linear relationship with the output of the OSL dosimeters (R2 = 0.96). Fading was found to affect dosimeter readings during the first two hours following exposure but had no effect during the remaining 60‐h period observed. No significant angular dependence was observed for the exposure conditions used in this study (with p‐values ranging from 0.9 to 0.26 for all t‐tests). Dosimeter counts varied linearly with absorbed dose when measured in the center and 12 o'clock positions of the CTDI phantoms. These linear models of counts versus absorbed dose had overlapping 95% confidence intervals for the intercepts but not for the slopes. (2) When dosimeters were positioned using safety glasses, there was no adverse effect on image quality, and there was no statistically significant difference between this placement and placement of the dosimeters directly on the eyes of the phantom (p = 0.24). (3) When using organ‐based tube current modulation, the dose to the lens of the eye was reduced between 19% and 43%, depending on the scan protocol used and the positioning of the phantom. Furthermore, the amount of dose reduction was significantly affected by the vertical position of the phantom, with the largest reduction in dose seen when the phantom was centered in the gantry.

Conclusions:

(1) An appropriate correction factor, specific to CT scanning, was developed to account for depletion and fading characteristics of the dosimeters. Additionally, an equation to convert dosimeter counts to absorbed dose was established. (2) The use of plastic safety glasses was validated as an appropriate positioning device when measuring dose to the lens of the eye. (3) The use of organ‐based tube current modulation can reduce dose to the lens of the eye during CT scanning. The amount of dose reduction, however, is largely influenced by the positioning of the anatomy in the gantry.
Determination of in vivo target search kinetics of regulatory noncoding RNA
Authors: Fei Jingyi , Singh Digvijay , Zhang Qiucen , Park Seongjin , Balasubramanian Divya , Golding Ido , Vanderpool Carin K. , Ha Taekjip
Published: March 2015

RNA kinetics may define regulatory hierarchy

The double-helical structure of DNA suggests immediately how nucleic acid polymers can recognize and bind to homologous sequences. Target recognition by RNA is vital in many biological processes. Fei
et al.
used super-resolution microscopy of tagged RNAs and computer modeling to understand how RNA-RNA base-pairing reactions occur in vivo. They studied a small RNA (sRNA) that targets a messenger RNA (mRNA) for degradation in bacteria. They observed a slow rate of association as the sRNA searched for its mRNA target, but thereafter a fast rate of dissociation. This explains the need for high concentrations of sRNA to cause mRNA degradation. The sRNA found different target mRNAs at different rates, allowing the generation of a regulatory hierarchy.

Science
, this issue p.
1371
Biologists devise invasion plan for mutations
Authors: Bohannon John
Published: March 2015

“Gene drive” technique could fight insect-borne disease, but some call for safeguards.
Faith in science
Huxley's Church and Maxwell's Demon: From Theistic Science to Naturalistic Science
Matthew Stanley
University of Chicago Press, 2014. 372 pp.
Authors: Smith Crosbie
Published: March 2015

The complex relationship between science and religion in Victorian Britain
A mitochondrial UPR-mediated metabolic checkpoint regulates hematopoietic stem cell aging
Authors: Mohrin Mary , Shin Jiyung , Liu Yufei , Brown Katharine , Luo Hanzhi , Xi Yannan , Haynes Cole M. , Chen Danica
Published: March 2015

Keeping stem cells in tip top condition

Stem cells are important in the maintenance and growth of tissues. For the health of the organism as a whole, it is important that only healthy stem cells be used. Mohrin
et al.
elucidated a regulatory branch of the mitochondrial unfolded protein response that is coupled to cellular energy metabolism and proliferation in stem cells (see the Perspective by Ocampo and Belmonte). Mitochondrial protein folding stress triggered a metabolic checkpoint that regulates the cell cycle. Deregulation of this pathway interfered with stem cell quiescence and compromised regenerative function.

Science
, this issue p.
1374
; see also p.
1319
Taming CH
5
+
, the “enfant terrible” of chemical structures
Authors: Oka Takeshi
Published: March 2015

Ion-counting spectroscopy reveals the low-energy states of a molecule with highly dynamic bonds

[Also see Report by

Asvany
et al.

]
Building supermicelles from simple polymers
Authors: Lee In-Hwan , Shin Suyong , Choi Tae-Lim
Published: March 2015

Precise control of the polymer building blocks enables synthesis of a range of micrometer-scale structures

[Also see Report by

Qiu
et al.

]
Identification of Pertussis-Specific Effector Memory T Cells in Preschool Children
Authors: de Rond Lia , Schure Rose-Minke , Öztürk Kemal , Berbers Guy , Sanders Elisabeth , van Twillert Inonge , Carollo Maria , Mascart Françoise , Ausiello Clara M. , van Els Cecile A. C. M. , Smits Kaat , Buisman Anne-Marie
Published: March 2015

Whooping cough remains a problem despite vaccination, and worldwide resurgence of pertussis is evident. Since cellular immunity plays a role in long-term protection against pertussis, we studied pertussis-specific T-cell responses. Around the time of the preschool acellular pertussis (aP) booster dose at 4 years of age, T-cell memory responses were compared in children who were primed during infancy with either a whole-cell pertussis (wP) or an aP vaccine. Peripheral blood mononuclear cells (PBMCs) were isolated and stimulated with pertussis vaccine antigens for 5 days. T cells were characterized by flow-based analysis of carboxyfluorescein succinimidyl ester (CFSE) dilution and CD4, CD3, CD45RA, CCR7, gamma interferon (IFN-γ), and tumor necrosis factor alpha (TNF-α) expression. Before the aP preschool booster vaccination, both the proliferated pertussis toxin (PT)-specific CD4+and CD8+T-cell fractions (CFSEdim) were higher in aP- than in wP-primed children. Post-booster vaccination, more pertussis-specific CD4+effector memory cells (CD45RA−CCR7−) were induced in aP-primed children than in those primed with wP. The booster vaccination did not appear to significantly affect the T-cell memory subsets and functionality in aP-primed or wP-primed children. Although the percentages of Th1 cytokine-producing cells were alike in aP- and wP-primed children pre-booster vaccination, aP-primed children produced more Th1 cytokines due to higher numbers of proliferated pertussis-specific effector memory cells. At present, infant vaccinations with four aP vaccines in the first year of life result in pertussis-specific CD4+and CD8+effector memory T-cell responses that persist in children until 4 years of age and are higher than those in wP-primed children. The booster at 4 years of age is therefore questionable; this may be postponed to 6 years of age.
Refinement of Whole-Genome Multilocus Sequence Typing Analysis by Addressing Gene Paralogy
Authors: Zhang Ji , Halkilahti Jani , Hänninen Marja-Liisa , Rossi Mirko
Published: March 2015

We developed a user-friendly program, Genome Profiler (GeP), to refine whole-genome multilocus sequence typing analysis by addressing gene paralogy with conserved gene neighborhoods. In comparison to similar programs, GeP produced overall the best results in terms of accuracy and is thus a useful alternative to resolve relationships of bacterial isolates.
Comparison of the AmpliVue, BD Max System, and
illumi
gene Molecular Assays for Detection of Group B Streptococcus in Antenatal Screening Specimens
Authors: Miller Shelley A. , Deak Eszter , Humphries Romney
Published: March 2015

The performances of the AmpliVue, BD Max, and
illumi
gene group B
Streptococcus
(GBS) nucleic acid amplification tests (NAATs) were compared to that of enriched culture for detection of GBS in antenatal screening specimens. Two hundred specimens were tested simultaneously with the NAATs, following 18 to 24 h of Lim broth enrichment; 15% of specimens were culture positive for GBS, whereas 31.5% were positive by at least one NAAT. All three NAATs were more sensitive (sensitivity, 90.9 to 100%) than culture (sensitivity, 53.6%).
Comparison of the Vidas C. difficile GDH Automated Enzyme-Linked Fluorescence Immunoassay (ELFA) with Another Commercial Enzyme Immunoassay (EIA) (Quik Chek-60), Two Selective Media, and a PCR Assay for
gluD
for Detection of Clostridium difficile in Fecal Samples
Authors: Davies K. A. , Berry C. E. , Morris K. A. , Smith R. , Young S. , Davis T. E. , Fuller D. D. , Buckner R. J. , Wilcox M. H.
Published: March 2015

Prevention and management of
Clostridium difficile
infection (CDI) can be improved by rapid and reliable diagnostics. The Vidas
C. difficile
glutamate dehydrogenase assay had performance comparable to that of the Quik Chek-60 assay (overall agreement, 95%) and a sensitivity of >93%; thus, it is suitable as the first test in two-stage algorithms for a CDI diagnosis.