bluuebunny/crossref_metadata_2025 huggingface dataset:
Stability of Geriatric Syndromes in Hospitalized Medicare Beneficiaries Discharged to Skilled Nursing Facilities
Authors: Simmons Sandra F. , Bell Susan , Saraf Avantika A. , Coelho Chris S. , Long Emily A. , Jacobsen J. M. L. , Schnelle John F. , Vasilevskis Eduard E.
Published: September 2016

Objectives

To assess multiple geriatric syndromes in a sample of older hospitalized adults discharged to skilled nursing facilities (SNFs) and subsequently to home to determine the prevalence and stability of each geriatric syndrome at the point of these care transitions.

Design

Descriptive, prospective study.

Setting

One large university‐affiliated hospital and four area SNFs.

Participants

Fifty‐eight hospitalized Medicare beneficiaries discharged to SNFs (N = 58).

Measurements

Research personnel conducted standardized assessments of the following geriatric syndromes at hospital discharge and 2 weeks after SNF discharge to home: cognitive impairment, depression, incontinence, unintentional weight loss, loss of appetite, pain, pressure ulcers, history of falls, mobility impairment, and polypharmacy.

Results

The average number of geriatric syndromes per participant was 4.4 ± 1.2 at hospital discharge and 3.8 ± 1.5 after SNF discharge. There was low to moderate stability for most syndromes. On average, participants had 2.9 syndromes that persisted across both care settings, 1.4 syndromes that resolved, and 0.7 new syndromes that developed between hospital and SNF discharge.

Conclusion

Geriatric syndromes were prevalent at the point of each care transition but also reflected significant within‐individual variability. These findings suggest that multiple geriatric syndromes present during a hospital stay are not transient and that most syndromes are not resolved before SNF discharge. These results underscore the importance of conducting standardized screening assessments at the point of each care transition and effectively communicating this information to the next provider to support the management of geriatric conditions.
Knowledge Translation Strategy to Reduce the Use of Potentially Inappropriate Medications in Hospitalized Elderly Adults
Authors: Cossette Benoit , Bergeron Josée , Ricard Geneviève , Éthier Jean‐François , Joly‐Mischlich Thomas , Levine Mitchell , Sene Modou , Mallet Louise , Lanthier Luc , Payette Hélène , Rodrigue Marie‐Claude , Brazeau Serge
Published: September 2016

Objectives

To evaluate the effect of a knowledge translation (KT) strategy to reduce potentially inappropriate medication (PIM) use in hospitalized elderly adults.

Design

Segmented regression analysis of an interrupted time series.

Setting

Teaching hospital.

Participants

Individuals aged 75 and older discharged from the hospital in 2013/14 (mean age 83.3, 54.5% female).

Intervention

The KT strategy comprises the distribution of educational materials, presentations by geriatricians, pharmacist–physician interventions based on alerts from a computerized alert system, and comprehensive geriatric assessments.

Measurements

Rate of PIM use (number of patient‐days with use of at least one PIM/number of patient‐days of hospitalization for individuals aged ≥75).

Results

For 8,622 patients with 14,071 admissions, a total of 145,061 patient‐days were analyzed. One or more PIMs were prescribed on 28,776 (19.8%) patient‐days; a higher rate was found for individuals aged 75 to 84 (24.0%) than for those aged 85 and older (14.4%) (P < .001), and in women (20.8%) than in men (18.6%) (P < .001). The drug classes most frequently accounting for the PIM were gastrointestinal agents (21%), antihistamines (18%), and antidepressants (17%). An absolute decrease of 3.5% (P < .001) of patient‐days with at least one PIM was observed immediately after the intervention.

Conclusion

A KT strategy resulted in decreased use of PIM in elderly adults in the hospital. Additional interventions will be implemented to maintain or further reduce PIM use.
Attitudes of Muslims Living in the United States Toward Long‐Term Care Decisions and Diagnosis Disclosure for Elderly Family Members
Authors: McLaughlin Matthew H. , Elahi Abdul , Ciesielski Janice , Pomerantz Sherry
Published: September 2016

This study explored the attitudes of Muslims living in the United States toward long‐term care decisions and diagnostic disclosure. Members of six mosques in New Jersey aged 40 and older agreed to participate in a telephone interview. Respondents were read medical scenarios and asked to indicate their preferences from a list of responses. Scenarios were: if they or a family member were disabled, who would they prefer to care for them; would they use a Muslim nursing home for themselves or loved one; who should be informed first if an individual had cancer or would die very soon (the individual or the individual's family); and whether these diagnoses should be disclosed to the individual's family without the individual's consent. If disabled, 62% (n = 103) of participants would prefer care at home, and 65.7% (n = 108) would prefer care at home for a disabled loved one. If there were a Muslim nursing home, 78.3% (n = 103) of participants would consider this facility for themselves and 76% (n = 127) would consider it for a loved one. Fifty‐six percent (n = 93) of participants believed the individual should be informed first of a cancer diagnosis, and 54.6% (n = 89) believed the individual should be informed first if their death was imminent. Disclosing an individual's cancer diagnosis to family members without the individual's consent was acceptable to 49.7% (n = 83) and disclosing his or her imminent death was acceptable to 55.1% (n = 92). Participants were from 21 countries. Participants from Western countries were most likely to believe individuals should be informed first about their cancer diagnosis or imminent death.
Effect of a Home‐Based Palliative Care Program on Healthcare Use and Costs
Authors: Brian Cassel J. , Kerr Kathleen M. , McClish Donna K. , Skoro Nevena , Johnson Suzanne , Wanke Carol , Hoefer Daniel
Published: September 2016

Objectives

To evaluate the nonclinical outcomes of a proactive palliative care program funded and operated by a health system for Medicare Advantage plan beneficiaries.

Design

Observational, retrospective study using propensity‐based matching.

Setting

A health system in southern California.

Participants

Individuals who received the intervention between 2007 and 2014 (n = 368) were matched with 1,075 comparison individuals within each of four disease groups: cancer, chronic obstructive pulmonary disease, heart failure, and dementia. All were known to be dead at the time of the retrospective study, were Medicare Advantage beneficiaries, and had 2 years of usage data before death. Median age at death for each disease group was older than 80.

Intervention

Home‐ and clinic‐based palliative care (PC) services provided by a multidisciplinary team.

Measurements

Outcomes included hospital costs, other healthcare costs, readmission rates, hospital admissions and bed days, intensive care unit use in final 30 days of life, and death within 30 days of an admission.

Results

Intervention participants in all four disease groups had less hospital use and lower hospital costs nonintervention participants, which drove lower overall healthcare costs. In the final 6 months of life, healthcare costs for the intervention groups stayed largely the same from month to month, whereas costs for comparison participants increased dramatically.

Conclusion

In the context of an alternative payment model in which the provider was “at risk” of bearing the costs of care, a proactive PC program helped to avoid the escalation in hospital use and costs commonly seen in the final months of life.
Esthetic perception of smile components by orthodontists, general dentists, dental students, artists, and laypersons
Authors: Sadrhaghighi Hooman , Zarghami Afsaneh , Sadrhaghighi Shahrzad , Eskandarinezhad Mahsa
Published: September 2016

Aim

In the present study, we sought to assess the esthetic perception and level of acceptability of variations in smile components, including dental midline, buccal corridor, vertical lip thickness, and the golden ratio, by orthodontists, general dentists, dental students, artists, and laypersons.

Methods

An attractive female smile was digitally manipulated with regard to four smile components: dental midline, buccal corridor, vertical lip thickness, and the golden ratio. The manipulated photographs (n=27) were randomly arranged in a photo album and scored by five groups of raters (n=50 in each group) from zero to 100 using a horizontal visual analog scale. The acceptability threshold of each component by the five groups was calculated using the Spearman and Wilcoxon tests.

Results

Orthodontists and laypersons had the same perception of midline deviations, with an acceptability threshold lower than that of artists and general dentists. Only orthodontists perceived variations of buccal corridor (by 20%). Changes in vertical lip thickness were not perceived by any group. Orthodontists, general dentists, and laypersons had similar perceptions of variations in the golden ratio. Dental students and artists did not perceive variations in this component.

Conclusion

Professional dental training can affect the esthetic judgement of smiles in individuals.
Mammaglobin and DOG‐1 expression in polymorphous low‐grade adenocarcinoma: an appraisal of its origin and morphology
Authors: Montalli Victor Angelo Martins , Passador‐Santos Fabricio , Martinez Elizabeth Ferreira , Furuse Cristiane , Aguiar Maria Cássia , Soares Fernando Augusto , Soares Andresa Borges , Brown Amy Louise , de Araújo Ney Soares , de Araújo Vera Cavalcanti
Published: September 2016

Background

Polymorphous low‐grade adenocarcinoma (PLGA) remains a diagnostic challenge for most pathologists due to its large spectrum of histological patterns. In this study, the expression of two new markers recently described for salivary gland tumors was studied in PLGA.

Methods

The morphology of 33 cases of PLGA was carefully evaluated using hematoxylin‐and‐eosin‐stained sections and confirmed by immunohistochemistry for cytokeratin 7, vimentin, and S‐100. Periodic acid–Schiff with diastase digestion was also used. The expression of mammaglobin and DOG‐1 was carried out using the EnVision System. Mammaglobin was assessed according to the percentage of positively stained tumor cells, while DOG‐1 was evaluated according to its presence and site. For MCM‐2 and Ki‐67, markers of proliferation, the labeling index of cell nuclei positivity was evaluated using total cell number. The ETV6‐NTRK3 fusion was examined by fluorescence in situ hybridization analysis.

Results

The histological patterns of the tumor were classified as lobular or non‐lobular. For the non‐lobular pattern, tubular, cribriform, glomeruliform, trabecular, and papillary patterns were observed. Mammaglobin was present in all PLGA cases, and its expression was stronger (P = 0.01) in the lobular than in the non‐lobular pattern. The expression of DOG‐1 was present in the apical portion and cytoplasm of the cells. Proliferation markers were low for all cases independent of histological pattern.

Conclusions

Polymorphous low‐grade adenocarcinoma has been confirmed to originate from the intercalated duct and to feature high expression of mammaglobin in its lobular pattern resembling that of mammary secretory analogue carcinoma, except for the ETV6 gene rearrangement.
Non‐cannibalistic tumor cells of oral squamous cell carcinoma can express phagocytic markers
Authors: Sarode Sachin C. , Sarode Gargi S. , Chuodhari Shakira , Patil Shankargouda
Published: September 2016

Background

CD68 and lysozyme expression in cannibalistic tumor cells of oral squamous cell carcinoma (OSCC) is well established. Transformation of cancer cells into cannibalistic cells is a process involving sequential events. Initial event could be genetic expression of proteins that is required for execution of cannibalism. Hence, it is quite possible that some non‐cannibalistic tumor cells can also show expression of cannibalistic markers (CD68 and lysozyme).

Methodology

Formalin‐fixed tissues of 30 OSCC cases with cellular cannibalism (CC) (positive control), 30 OSCC cases without CC, and 17 normal oral epithelium specimens (negative control) were subjected to immunohistochemical analysis for CD68 and lysozyme expression.

Results

OSCC with CC showed CD68 and lysozyme expression in 30 (100%) cases each {CD68: [weak: 21 (70%), strong: 9 (30%)]; lysozyme: [weak: 24 (80%), strong: 6 (20%)]}. In OSCCs without CC, CD68‐positive tumor cells were present in 13 (43.33%) cases [weak: 10 (33.33%); strong: 3 (10%)] and lysozyme expression was present in 13 (43.33%) cases [weak: 12 (40%); strong: 1 (3.33%)]. Control group showed negative expression for CD68 and lysozyme in the oral epithelium. The CD68 and lysozyme expression in OSCCs without CC, OSCCs with CC, and control group showed statistically significant differences (P < 0.001). Significant correlation was also observed between CD68 and lysozyme expression and different grades of OSCC.

Conclusion

CD68 and lysozyme expression in non‐cannibalistic tumor cells of OSCC can be related to CC.
Use of dual‐phase contrast computed tomography for evaluation of the normal canine male genital tract
Authors: Dirrig H. , Drees R. , Lam R.
Published: September 2016

Objectives

To evaluate the use of dual‐phase contrast‐enhanced computed tomography for the depiction of the features of the male genital tract, highlighting differences between entire and neutered dogs.

Methods

Computed tomography exams of 23 entire and 23 neutered male dogs with no history of urogenital disease were included in this retrospective study, with exams acquired pre‐, 30 and 98·9 ±27·4 seconds after intravenous contrast administration. The genital structures were subjectively evaluated for visibility, contrast enhancement and enhancement pattern and differences between entire and neutered dogs were described. Objective measurements of attenuation and size of the prostatic tissue were acquired.

Results

The root, body and glans of the penis could be evaluated in all dogs and appeared larger in entire dogs, though objective measurements could not be reliably made because these structures are small and curved. There was contrast enhancement of the cavernous structures, most reliably in the bulb and corpus spongiosum and most frequently in entire dogs in the delayed post‐contrast phase. In entire dogs, the small testicular vessels most commonly had a vermiform shape in the early post‐contrast phase, and a homogeneous appearance in the delayed phase. Sternal recumbency with the coxofemoral joints extended improved visibility of the genital structures.

Clinical Significance

Dual‐phase contrast‐enhanced computed tomography is useful for depiction of the structures of the male genital tract, with the early phase especially highlighting the vascular and the delayed phase the cavernous structures.
Early gut colonization byBifidobacterium breveandB. catenulatumdifferentially modulates eczema risk in children at high risk of developing allergic disease
Authors: Ismail Intan H. , Boyle Robert J. , Licciardi Paul V. , Oppedisano Frances , Lahtinen Sampo , Robins‐Browne Roy M. , Tang Mimi L.K.
Published: September 2016

Background

An altered compositional signature and reduced diversity of early gut microbiota are linked to development of allergic disease. We investigated the relationship between dominantBifidobacteriumspecies during the early post‐natal period and subsequent development of allergic disease in the first year of life.

Methods

Faecal samples were collected at age 1 week, 1 month and 3 months from 117 infants at high risk of allergic disease.Bifidobacteriumspecies were analysed by quantitativePCRand terminal restriction fragment length polymorphism. Infants were examined at 3, 6 and 12 months, and skin prick test was performed at 12 months. Eczema was diagnosed according to theUKWorking Party criteria.

Results

The presence ofB. catenulatumat 3 months was associated with a higher risk of developing eczema (ORadj= 4.5; 95%CI: 1.56–13.05, padj= 0.005). Infants colonized withB. breveat 1 week (ORadj= 0.29; 95%CI: 0.09–0.95, padj= 0.04) and 3 months (ORadj= 0.15; 95%CI: 0.05–0.44, padj= 0.00001) had a reduced risk of developing eczema. Furthermore, the presence ofB. breveat 3 months was associated with a lower risk of atopic sensitization at 12 months (ORadj= 0.38; 95%CI: 0.15–0.98, padj= 0.05).B. brevecolonization patterns were influenced by maternal allergic status, household pets and number of siblings.

Conclusions

Temporal variations inBifidobacteriumcolonization patterns early in life are associated with later development of eczema and/or atopic sensitization in infants at high risk of allergic disease. Modulation of the early microbiota may provide a means to prevent eczema in high‐risk infants.
Serum biomarkers for allergy in children
Authors: Knipping Karen , Knippels Léon M.J. , Dupont Christophe , Garssen Johan
Published: September 2016

A large number of studies investigating various biomarkers for allergy have been published over the past decades. The aim of this review was to evaluate these biomarkers on their diagnostic and/or predictive value. To this date, no single or specific biomarker for allergy has been identified. As allergy is not one disease, but a collection of a number of allergic conditions, it is more plausible a combination of clinical history, clinical readouts, and diagnostic markers will be needed.
The prevalence of atopic diseases and the patterns of sensitization in adolescence
Authors: Christiansen Elisabeth Soegaard , Kjaer Henrik Fomsgaard , Eller Esben , Bindslev‐Jensen Carsten , Høst Arne , Mortz Charlotte Gotthard , Halken Susanne
Published: September 2016

Background

Atopic diseases are among the most common chronic diseases in adolescents, and it is uncertain whether the prevalence of atopic diseases has reached a plateau or is still increasing. The use of the ISAAC (International Study of Asthma and Allergy in Childhood) questionnaire has provided comparable prevalence rates from many countries, whereas studies including clinical examinations and strict diagnostic criteria are scarce. We aimed to investigate the prevalence of atopic diseases, the pattern of sensitization, and comorbidities at 14 years in a prospective birth cohort.

Methods

The children were examined eight times from birth to 14 years. Visits included questionnaire‐based interviews, clinical examination, skin prick test, and specific IgE.

Results

Follow‐up rate at 14 years was 66.2%. The 12‐month prevalence of any atopic disease was high (40.3%) mostly due to a high prevalence of rhinoconjunctivitis (32.8%), whereas the prevalence of asthma was 12.9% and of atopic dermatitis 8.1%. In children with at least one atopic disease, 60% were sensitized, while only 16% of those without atopic diseases were sensitized. The frequency of sensitization depended on the phenotype. Among children with rhinoconjunctivitis only, rhinoconjunctivitis with concomitant asthma or atopic dermatitis or both 62.5%, 81.5%, 70%, and 100%, respectively, were sensitized, whereas it was 7.7% and 33.3% of children with only asthma or atopic dermatitis.

Conclusion

The prevalence of rhinoconjunctivitis was high in adolescence. Children with rhinoconjunctivitis with and without comorbidities were frequently sensitized. Children with asthma without concomitant allergic rhinoconjunctivitis were rarely sensitized.
Dual Sourcing Inventory Systems: On Optimal Policies and the Value of Costless Returns
Authors: Janakiraman Ganesh , Seshadri Sridhar
Published: September 2016

We study dual sourcing inventory systems with backordering and with stationary, stochastic demands. The two supply sources differ in their unit prices and lead times. We focus on the option of making costless returns to the cheaper, longer leadtime supplier. We show that the value of this option is zero. Our analysis leading to this result includes the derivation of several structural properties of the optimal policies for dual sourcing systems with and without the return option.
The Role of Industry Studies and Public Policies in Production and Operations Management
Authors: Joglekar Nitin R. , Davies Jane , Anderson Edward G.
Published: September 2016

The research domain Industry Studies and Public Policy (IS&PP) seeks to further our understanding of industrial practices and managerial challenges by explicitly considering contextual details in the design and interpretation of research studies. These details can be vital considerations when shaping public policies. This article reviews a sample of IS&PP publications and analyzes the content of 180 selected papers—85 papers published in the Production and Operations Management (POM) journal and 95 papers published in related journals between 1992 and 2014. Our analysis of the sample dataset and examination of exemplar papers provide four findings. First, studies in different industries emphasize different themes of operational decisions. This difference in emphasis reveals potential research opportunities, especially for conducting inter‐industry studies. Second, our analysis reveals a shift in focus over time. Earlier studies contain a mix of benchmarks and inter‐industry comparisons, while later studies tend to be context‐specific, intra‐industry studies. Third, we report on empirics → analytics → empirics cycles that reveal gaps for building novel theories. Finally, we observe that the relationship between POM decisions and public policy is bi‐directional. This highlights the need to jointly examine operational decisions with policy considerations, especially in information goods, healthcare, sustainable operations and high‐tech manufacturing industries.
Effective Medical Surplus Recovery
Authors: Atasu Atalay , Toktay Beril , Yeo Wee Meng , Zhang Can
Published: September 2016

We analyze not‐for‐profit Medical Surplus Recovery Organizations (MSROs) that manage the recovery of surplus (unused or donated) medical products to fulfill the needs of underserved healthcare facilities in the developing world. Our work is inspired by an award‐winning North American non‐governmental organization (NGO) that matches the uncertain supply of medical surplus with the receiving parties’ needs. In particular, this NGO adopts a recipient‐driven resource allocation model, which grants recipients access to an inventory database, and each recipient selects products of limited availability to fill a container based on its preferences. We first develop a game theoretic model to investigate the effectiveness of this approach. This analysis suggests that the recipient‐driven model may induce competition among recipients and lead to a loss in value provision through premature orders. Further, contrary to the common wisdom from traditional supply chains, full inventory visibility in our setting may accelerate premature orders and lead to loss of effectiveness. Accordingly, we identify operational mechanisms to help MSROs deal with this problem. These are: (i) appropriately selecting container capacities while limiting the inventory availability visible to recipients and increasing the acquisition volumes of supplies, (ii) eliminating recipient competition through exclusive single‐recipient access to MSRO inventory, and (iii) focusing on learning recipient needs as opposed to providing them with supply information, and switching to a provider‐driven resource allocation model. We use real data from the NGO by which the study was inspired and show that the proposed improvements can substantially increase the value provided to recipients.
Seasonal Changes in Central England Temperatures
Authors: Proietti Tommaso , Hillebrand Eric
Published: September 2016

The aim of the paper is to assess how climate change is reflected in the variation of the seasonal patterns of the monthly central England temperature time series between 1772 and 2013. In particular, we model changes in the amplitude and phase of the seasonal cycle. Starting from the seminal work of Thomson, various studies have documented a shift in the phase of the annual cycle, implying an earlier onset of the spring season at various European locations. A significant reduction in the amplitude of the seasonal cycle is also documented. The literature so far has concentrated on the measurement of this phenomenon by various methods, among which complex demodulation and wavelet decompositions are prominent. We offer new insight by considering a model that allows for seasonally varying deterministic and stochastic trends, as well as seasonally varying auto-correlation and residual variances. The model can be summarized as containing a permanent and a transitory component, where global warming is captured in the permanent component, on which the seasons load differentially. The phase of the seasonal cycle, in contrast, seems to be following the trend that was identified by Thomson with Earth's precession in a stable manner. We identify the reported fluctuations as transitory.
Health Losses at The End of Life: A Bayesian Mixed Beta Regression Approach
Authors: Gheorghe Maria , Picavet Susan , Verschuren Monique , Brouwer Werner B. F. , Baal Pieter H. M.
Published: September 2016

The relationship between aging, health and healthcare expenditures is of central importance to academics and public policy makers. Generally, it is observed that, with advancing age, health deteriorates and healthcare expenditures increase. This seems to imply that increases in life expectancy would strongly increase both the demand for healthcare expenditures and the number of years lived in poor health. Previous research has shown that such straightforward conclusions may be flawed. For example, it has been established that not age but ‘time to death’ is the main driver of increased healthcare expenditures at advanced ages. The paper extends this line of research by investigating the relationship between age, time to death and health, the last being longitudinally measured via a health-related quality-of-life questionnaire. We propose an approach for modelling the health-related quality-of-life outcome that accounts for both the non-standard nature of this response variable (e.g. bounded, left skewed or heteroscedastic) and the panel structure of the data. Analyses were performed within a Bayesian framework. We found that health losses are centred in the final phase of life, which indicates that future increases in longevity will not necessarily increase life years spent in poor health. This may alleviate the consequences of population aging.
On Estimation of Optimal Treatment Regimes for Maximizingt-Year Survival Probability
Authors: Jiang Runchao , Lu Wenbin , Song Rui , Davidian Marie
Published: September 2016

A treatment regime is a deterministic function that dictates personalized treatment based on patients’ individual prognostic information. There is increasing interest in finding optimal treatment regimes, which determine treatment at one or more treatment decision points to maximize expected long-term clinical outcomes, where larger outcomes are preferred. For chronic diseases such as cancer or human immunodeficiency virus infection, survival time is often the outcome of interest, and the goal is to select treatment to maximize survival probability. We propose two non-parametric estimators for the survival function of patients following a given treatment regime involving one or more decisions, i.e. the so-called value. On the basis of data from a clinical or observational study, we estimate an optimal regime by maximizing these estimators for the value over a prespecified class of regimes. Because the value function is very jagged, we introduce kernel smoothing within the estimator to improve performance. Asymptotic properties of the proposed estimators of value functions are established under suitable regularity conditions, and simulation studies evaluate the finite sample performance of the regime estimators. The methods are illustrated by application to data from an acquired immune deficiency syndrome clinical trial.
Computational Investigation of Transmural Differences in Left Ventricular Contractility
Authors: Wang Hua , Zhang Xiaoyan , Dorsey Shauna M. , McGarvey Jeremy R. , Campbell Kenneth S. , Burdick Jason A. , Gorman Joseph H. , Pilla James J. , Gorman Robert C. , Wenk Jonathan F.
Published: September 2016

Myocardial contractility of the left ventricle (LV) plays an essential role in maintaining normal pump function. A recent ex vivo experimental study showed that cardiomyocyte force generation varies across the three myocardial layers of the LV wall. However, the in vivo distribution of myocardial contractile force is still unclear. The current study was designed to investigate the in vivo transmural distribution of myocardial contractility using a noninvasive computational approach. For this purpose, four cases with different transmural distributions of maximum isometric tension (Tmax) and/or reference sarcomere length (lR) were tested with animal-specific finite element (FE) models, in combination with magnetic resonance imaging (MRI), pressure catheterization, and numerical optimization. Results of the current study showed that the best fit with in vivo MRI-derived deformation was obtained when Tmax assumed different values in the subendocardium, midmyocardium, and subepicardium with transmurally varying lR. These results are consistent with recent ex vivo experimental studies, which showed that the midmyocardium produces more contractile force than the other transmural layers. The systolic strain calculated from the best-fit FE model was in good agreement with MRI data. Therefore, the proposed noninvasive approach has the capability to predict the transmural distribution of myocardial contractility. Moreover, FE models with a nonuniform distribution of myocardial contractility could provide a better representation of LV function and be used to investigate the effects of transmural changes due to heart disease.
Patient-Specific Computational Analysis of Ventricular Mechanics in Pulmonary Arterial Hypertension
Authors: Xi Ce , Latnie Candace , Zhao Xiaodan , Tan Ju Le , Wall Samuel T. , Genet Martin , Zhong Liang , Lee Lik Chuan
Published: September 2016

Patient-specific biventricular computational models associated with a normal subject and a pulmonary arterial hypertension (PAH) patient were developed to investigate the disease effects on ventricular mechanics. These models were developed using geometry reconstructed from magnetic resonance (MR) images, and constitutive descriptors of passive and active mechanics in cardiac tissues. Model parameter values associated with ventricular mechanical properties and myofiber architecture were obtained by fitting the models with measured pressure–volume loops and circumferential strain calculated from MR images using a hyperelastic warping method. Results show that the peak right ventricle (RV) pressure was substantially higher in the PAH patient (65 mmHg versus 20 mmHg), who also has a significantly reduced ejection fraction (EF) in both ventricles (left ventricle (LV): 39% versus 66% and RV: 18% versus 64%). Peak systolic circumferential strain was comparatively lower in both the left ventricle (LV) and RV free wall (RVFW) of the PAH patient (LV: −6.8% versus −13.2% and RVFW: −2.1% versus −9.4%). Passive stiffness, contractility, and myofiber stress in the PAH patient were all found to be substantially increased in both ventricles, whereas septum wall in the PAH patient possessed a smaller curvature than that in the LV free wall. Simulations using the PAH model revealed an approximately linear relationship between the septum curvature and the transseptal pressure gradient at both early-diastole and end-systole. These findings suggest that PAH can induce LV remodeling, and septum curvature measurements may be useful in quantifying transseptal pressure gradient in PAH patients.
A Real-Time Programmable Pulsatile Flow Pump for In Vitro Cardiovascular Experimentation
Authors: Mechoor Rahul Raj , Schmidt Tyler , Kung Ethan
Published: September 2016

Benchtop in vitro experiments are valuable tools for investigating the cardiovascular system and testing medical devices. Accurate reproduction of the physiologic flow waveforms at various anatomic locations is an important component of these experimental methods. This study discusses the design, construction, and testing of a low-cost and fully programmable pulsatile flow pump capable of continuously producing unlimited cycles of physiologic waveforms. It consists of a gear pump actuated by an AC servomotor and a feedback algorithm to achieve highly accurate reproduction of flow waveforms for flow rates up to 300 ml/s across a range of loading conditions. The iterative feedback algorithm uses the flow error values in one iteration to modify the motor control waveform for the next iteration to better match the desired flow. Within four to seven iterations of feedback, the pump replicated desired physiologic flow waveforms to within 2% normalized RMS error (for flow rates above 20 mL/s) under varying downstream impedances. This pump device is significantly more affordable (∼10% of the cost) than current commercial options. More importantly, the pump can be controlled via common scientific software and thus easily implemented into large automation frameworks.
Mechanical Instabilities in Perfect Crystals: From Dislocation Nucleation to Bucklinglike Modes
Authors: Garg Akanksha , Maloney Craig E.
Published: September 2016

We perform atomistic simulations of nanoindentation on Lennard–Jones 2D hexagonal crystals. In this work, we find a new spatially extended buckling-like mode of instability, which competes with the previously known instability governed by dislocation-dipole nucleation. The geometrical parameters governing these instabilities are the lattice constant, a, the radius of curvature of the indenter, R, and the thickness of the indenter layer, Ly. Whereas dislocation nucleation is a saddle-node bifurcation governed by R/a, the buckling-like instability is a pitchfork bifurcation (like classical Euler buckling) governed by R/Ly. The two modes of instability exhibit strikingly different behaviors after the onset of instability. The dislocation nucleation mode results in a stable final configuration containing a surface step and a stable dislocation at some depth beneath the surface, while the buckling modes are always followed immediately by subsequent nucleation of many dislocation dipoles. We show that this subsequent dislocation nucleation is also observed immediately after buckling in free standing rods, but only for rods which are of sufficiently wide aspect ratio, while thinner rods exhibit stable buckling followed only later by dislocation nucleation in the buckled state. Finally, we study the utility of several recently proposed local and quasi-local stability criteria in detecting the buckling mode. We find that the so-called Λ criterion, based on the stability of a representative homogeneously deformed lattice, is surprisingly useful in detecting the transition from dislocation-type instability to buckling-type instability.
Compound Synchronization Based on Memristive Cellular Neural Network of Chaos System
Authors: Zhang Xiaohong , Liao Linyu
Published: September 2016

As a especial type of synchronous method, compound synchronization is designed by multiple drive systems and response systems. In this paper, a new type of compound synchronization of three drive systems and two response systems is investigated. According to synchronous control of five memristive cellular neural networks (CNNs), the theoretical analysis and demonstration are given out by using Lyapunov stability theory. The corresponding numerical simulations and synchronous performance analysis are supplied to verify the feasibility and scalability of compound synchronization design.
Experimental and Numerical Study on Dynamic Properties of Viscoelastic Microvibration Damper Considering Temperature and Frequency Effects
Authors: Xu Chao , Xu Zhao-Dong , Ge Teng , Liao Ya-Xin
Published: September 2016

This work presents an experimental and numerical study on the dynamic properties of viscoelastic (VE) microvibration damper under microvibration conditions at different frequencies and temperatures. The experimental results show that the storage modulus and the loss factor of VE microvibration damper both increase with increasing frequency but decrease with increasing temperature. To explicitly and accurately represent the temperature and frequency effects on the dynamic properties of VE microvibration damper, a modified standard solid model based on a phenomenological model and chain network model is proposed. A Gaussian chain spring and a temperature-dependent dashpot are employed to reflect the temperature effect in the model, and the frequency effect is considered with the nature of the standard solid model. Then, the proposed model is verified by comparing the numerical results with the experimental data. The results show that the proposed model can accurately describe the dynamic properties of VE microvibration damper at different temperatures and frequencies.
An Implantable Accelerometer-Based Heart-Monitoring Device With Improved Positional Stability
Authors: Tjulkins Fjodors , Thai Nguyen Anh-Tuan , Andreassen Erik , Hoff Lars , Grymyr Ole-Johannes , Halvorsen Per Steinar , Imenes Kristin
Published: September 2016

This paper reports recent results from an ongoing effort to develop an implantable accelerometer-based heart-monitoring device for ischemia monitoring. The latest device prototype utilizes a new and more compact accelerometer (1.2 × 1.5 × 0.8 mm3), a prototype device from Bosch SensorTec, Reutlingen, Germany. This paper presents the fabrication and testing of the device, including an explorative study of the effect of the capsule shape on the stability of the implanted device in the heart tissue. The stability study indicated sufficient stability of the device and a higher resistance to retraction for one of the capsule designs. The device was able to carry out acceleration monitoring and it meets the leakage current requirements of the IEC60601 standard.
Design, Fabrication, and Testing of a Needle-Sized Wrist for Surgical Instruments
Authors: Swaney Philip J. , York Peter A. , Gilbert Hunter B. , Burgner-Kahrs Jessica , Webster Robert J.
Published: September 2016

This paper presents a miniature wrist that can be integrated into needle-sized surgical instruments. The wrist consists of a nitinol tube with asymmetric cutouts that is actuated by a single tendon to provide high distal curvature. We derive and experimentally validate kinematic and static models for the wrist and describe several prototype wrists, illustrating the straightforward fabrication and scalability of the design. We experimentally investigate fatigue life, the concept of tip-first bending, and practical use of the wrist with a concentric tube robot in an endonasal surgical scenario.
A Comprehensive Contact Analysis of Planetary Roller Screw Mechanism
Authors: Fu Xiaojun , Liu Geng , Ma Shangjun , Tong Ruiting , Lim Teik C.
Published: September 2016

A comprehensive contact analysis model to determine the contact positions and clearances of mating thread surfaces in the planetary roller screw mechanism (PRSM) is proposed in this paper. By introducing a three-dimensional clearance vector, the modified conditions of continuous tangency of mating surfaces are established, in which the clearances along all the directions and contact positions of an arbitrary pair of mating surfaces can be calculated. The deviations of the screw, roller, and nut from their nominal positions are considered in the transformation matrices, which describe the position relations of the screw, roller, and nut. Then, the equations of thread surfaces with deviations are derived. Using the modified conditions and the equations of surfaces, the meshing equations at the screw–roller and nut–roller interfaces are derived to compute the clearances along all the directions and contact positions of mating thread surfaces on each pair of thread teeth in the imperfect PRSM. The effectiveness of the proposed model is verified by comparing the contact positions at the screw–roller interface with those from the previously published model. Then, the effect of the direction of clearance vector on the clearances and contact positions is analyzed and discussed. Because of the roller deviation, the clearances between multiple pairs of thread teeth are no longer identical, and the contact positions of a pair of mating thread surfaces on different pairs of thread teeth are different. Also, the parameters of a PRSM without clearances can be obtained from the proposed model in the design process.
A Constraint Satisfaction Algorithm for the Generalized Inverse Phase Stability Problem
Authors: Galvan Edgar , Malak Richard J. , Gibbons Sean , Arroyave Raymundo
Published: September 2016

Researchers have used the (calculation of phase diagram) CALPHAD method to solve the forward phase stability problem of mapping from specific thermodynamic conditions (material composition, temperature, pressure, etc.) to the associated phase constitution. Recently, optimization has been used to solve the inverse problem: mapping specific phase constitutions to the thermodynamic conditions that give rise to them. These pointwise results, however, are of limited value since they do not provide information about the forces driving the point to equilibrium. In this paper, we investigate the problem of mapping a desirable region in the phase constitution space to corresponding regions in the space of thermodynamic conditions. We term this problem the generalized inverse phase stability problem (GIPSP) and model the problem as a continuous constraint satisfaction problem (CCSP). In this paper, we propose a new CCSP algorithm tailored for the GIPSP. We investigate the performance of the algorithm on Fe–Ti binary alloy system using ThermoCalc with the TCFE7 database against a related algorithm. The algorithm is able to generate solutions for this problem with high performance.
Study on Dimensional Tolerances Required for Miniature C(T) Specimens
Authors: Miura Naoki , Momoi Yasunori , Yamamoto Masato
Published: September 2016

The Master Curve approach using miniature C(T) specimens with 4 mm thickness is promising for directly determining the reference temperature of reactor pressure vessel (RPV) steels because they can be taken from the broken halves of the Charpy specimens used in the surveillance program to monitor neutron irradiation embrittlement. The relative dimensional tolerances of standard C(T) specimens are provided in the present ASTM E1921 standard; consequently, the absolute dimensional tolerances are stricter for smaller specimens. In this study, the effect of the tolerances of key dimensions on the elastic–plastic equivalent stress intensity factor derived from the J-integral, KJ, was calculated using three-dimensional finite-element analysis. Even if the dimensional tolerances for the miniature C(T) specimens based on the present standard were mitigated in some degree (as examples, the tolerance of specimen thickness of ±0.08 mm was mitigated to ±0.1 mm; and the tolerance of specimen width of ±0.04 mm was mitigated to ±0.1 mm), the variations of KJ and the reference temperature were negligibly small. Furthermore, the use of the mitigated dimensional tolerances with adequate accuracy for evaluating the fracture toughness was ascertained.
Performance-Based Reliability of ASME Piping Design Equations
Authors: Gupta Abhinav , Saigal Rakesh K. , Ryu Yonghee
Published: September 2016

In this paper, we present an exploratory study on the evaluation of reliability levels associated with the piping design equations specified by ASME Boiler and Pressure Vessel (BPV) Code, Section III. Probabilistic analyses are conducted to evaluate reliability levels in straight pipe segments with respect to performance functions that characterize the different failure criteria using advanced first-order reliability method (AFORM). One important failure criterion considered in this study relates to the plastic instability which forms the basis of piping design equations for emergency and faulted load level conditions as defined in the ASME code. The code-specified definition of plastic instability is based on the evaluation of a collapse moment which is defined using the moment–curvature curve for a particular component. In this study, we use elastic-perfectly plastic, bilinear kinematic hardening, and multilinear kinematic hardening stress–strain curves to develop closed-form expressions for the moment–curvature relationship in a straight unpressurized pipe. Both the pressurized and the unpressurized loading conditions are considered. The closed-form reliability is evaluated using Monte Carlo simulation because of the complex nature of the closed-form expression. The reliability values are calculated with respect to the maximum allowable moment specified by the code design equations that use deterministic safety factors.
Reference Curve of Fatigue Crack Growth for Ferritic Steels Under Negative R Ratio Provided by ASME Code Section XI
Authors: Hasegawa Kunio , Mares Vratislav , Yamaguchi Yoshihito
Published: September 2016

Reference curves of fatigue crack growth rates for ferritic steels in air environment are provided by the ASME Code Section XI Appendix A. The fatigue crack growth rates under negative R ratio are given as da/dN versus Kmax. It is generally well known that the growth rates decreases with decreasing R ratios. However, the da/dN as a function of Kmax are the same curves under R = 0, −1, and −2. In addition, the da/dN increases with decreasing R ratio for R < −2. This paper converts from da/dN versus Kmax to da/dN versus ΔKI, using crack closure U. It can be obtained that the growth rates da/dN as a function of ΔKI decrease with decreasing R ratio for −2 ≤ R < 0. It can be seen that the growth rate da/dN versus ΔKI is better equation than da/dN versus Kmax from the view point of stress ratio R. Furthermore, extending crack closure U to R = −5, it can be explained that the da/dN decreases with decreasing R ratio in the range of −5 ≤ R < 0. This tendency is consistent with the experimental data.
Performance Study and Energy Saving Process Analysis of Hybrid Absorption-Compression Refrigeration Cycles
Authors: Zhang Na , Lior Noam , Han Wei
Published: September 2016

In an attempt to improve the performance of hybrid absorption and mechanical vapor compression refrigeration systems and to determine the fundamental reasons for such improvements, two configurations of the hybrid refrigeration cycle with a booster compressor at different positions of the cycle (between the evaporation and the absorber, or between the generator and the condenser) are simulated and analyzed. The interrelation between the two subcycles and the hybridization principle have been explored and clarified. An NH3/H2O-based hybrid cycle is the basis of this simulation. It was found that (1) the hybrid cycle performance is mainly governed by the interaction between its two subcycles of mechanical compression and thermal compression and their respective energy efficiencies, and (2) the hybrid cycle primary energy-based coefficient of performance (COP) was higher by up to 15% (without internal heat recuperation) as compared with the nonhybrid absorption cycle, (3) in comparison with the nonhybrid absorption and vapor compression cycles working in the same temperature regions, the more efficient use of low-temperature heat by cascade utilization of the two energy inputs (heat rate and mechanical power) with different energy quality, and the enhanced refrigeration ability of low-temperature heat are the basic reasons for the hybrid cycle performance improvement and significant energy saving, (4) the hybrid cycle achieves an exergy efficiency of 36.5%, which is 27% higher than that of the absorption cycle, and 4.5% higher than the vapor compression cycle, achieving a thermal-driving exergy efficiency of 37.5% and mechanical work saving ratio up to 64%.