bluuebunny/crossref_metadata_2025 huggingface dataset:
Cerebrospinal fluid levels of synaptic and neuronal integrity correlate with gray matter volume and amyloid load in the precuneus of cognitively intact older adults
Authors: Schaeverbeke Jolien , Gille Benjamin , Adamczuk Katarzyna , Vanderstichele Hugo , Chassaing Emeric , Bruffaerts Rose , Neyens Veerle , Stoops Erik , Tournoy Jos , Vandenberghe Rik , Poesen Koen
Published: February 2019

The main pathophysiological alterations of Alzheimer's disease (AD) include loss of neuronal and synaptic integrity, amyloidogenic processing, and neuroinflammation. Similar alterations can, however, also be observed in cognitively intact older subjects and may prelude the clinical manifestation of AD. The objectives of this prospective cross‐sectional study in a cohort of 38 cognitively intact older adults were twofold: (i) to investigate the latent relationship among cerebrospinal fluid (CSF) biomarkers reflecting the main pathophysiological processes of AD, and (ii) to assess the correlation between these biomarkers and gray matter volume as well as amyloid load. All subjects underwent extensive neuropsychological examinations, CSF sampling, [18F]‐flutemetamol amyloid positron emission tomography, and T1‐weighted magnetic resonance imaging. A factor analysis revealed one factor that explained most of the variance in the CSF biomarker dataset clustering t‐tau, α‐synuclein, p‐tau181, neurogranin, BACE1, visinin‐like protein 1, chitinase‐3‐like protein 1 (YKL‐40), Aβ1–40 and Aβ1–38. Higher scores on this factor correlated with lower gray matter volume and with higher amyloid load in the precuneus. At the level of individual CSF biomarkers, levels of visinin‐like protein 1, neurogranin, BACE1, Aβ1–40, Aβ1–38, and YKL‐40 all correlated inversely with gray matter volume of the precuneus. These findings demonstrate that in cognitively intact older subjects, CSF levels of synaptic and neuronal integrity biomarkers, amyloidogenic processing and measures of innate immunity (YKL‐40) display a latent structure of common variance, which is associated with loss of structural integrity of brain regions implicated in the earliest stages of AD.

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Second‐line chemotherapy in biliary tract cancer: Outcome and prognostic factors
Authors: Schweitzer Nora , Kirstein Martha M. , Kratzel Anna‐Maria , Mederacke Young‐Seon , Fischer Mareike , Manns Michael P. , Vogel Arndt
Published: February 2019

Background & Aims

The prognosis of biliary tract cancer (BTC) is poor. Standard treatment for advanced BTC is a chemotherapy (CT) with gemcitabine and cisplatin. Phase III evidence for a second‐line (2L) CT is lacking. We aimed to investigate the feasibility of a 2L CT, to estimate the outcome and to identify prognostic markers.

Methods

Patients of our institution with advanced BTC between 2000 and 2015 receiving CT were included. Data were analysed in univariate and multivariate analysis.

Results

Three‐hundred and fifteen and 144 patients (45.7%) received first‐line (1L) and 2L CT respectively. The OS of patients receiving 2L CT was 16.67 and 9.9 months from the beginning of 1L and 2L CT respectively. The overall response rate and the disease control rate after 3 months were 9.7% and 33.6% respectively. Adverse events of grade 3 or more were observed in 26.1%. One patient died of gemcitabine‐related haemolytic uraemic syndrome. Age of more than 70 years was not associated with a poor outcome. In multivariate analysis, CEA levels of >3 µg/L (P = 0.004, hazard ratio [HR] 1.89, 95% CI 1.22, 2.91), cholinesterase (CHE) levels of <5 kU/L (P = 0.001, HR 2.11, 95% CI 1.34, 3.31) and leukocytosis (P = 0.001, HR 2.90, 95% CI 1.51, 5.56) were associated with poor survival.

Conclusions

Despite a relevant toxicity, our data suggest that 2L CT may be feasible in fit BTC patients. CEA elevation, leukocytosis and low CHE levels are unfavourable prognostic markers. Results from prospective randomized trials are urgently awaited.
The concomitant loss of APC and HNF4α in adult hepatocytes does not contribute to hepatocarcinogenesis driven by β‐catenin activation
Authors: Sartor Chiara , Bachelot Laura , Godard Cécile , Lager Franck , Renault Gilles , Gonzalez Frank J. , Perret Christine , Gougelet Angélique , Colnot Sabine
Published: February 2019

Background & Aims

Loss of hepatocyte nuclear factor‐4α (HNF4α), a critical factor driving liver development and differentiation, is frequently associated with hepatocellular carcinoma (HCC). Our recent data revealed that HNF4α level was decreased in mouse and human HCCs with activated β‐catenin signalling. In addition, increasing HNF4α level by miR‐34a inhibition slowed tumour progression of β‐catenin‐activated HCC in mice.

Methods

We generated a Hnf4aflox/flox/Apcflox/flox/TTR‐CreERT2 (Hnf4a/Apc∆Hep) mouse line and evaluated the impact of Hnf4a disruption on HCC development and liver homoeostasis.

Results

There was no significant impact of Hnf4a disruption on tumour onset and progression in Apc∆Hep model. However, we observed an unexpected phenotype in 28% of Hnf4a∆Hep mice maintained in a conventional animal facility, which presented disorganized portal triads, characterized by stenosis of the portal vein and increased number and size of hepatic arteries and bile ducts. These abnormal portal structures resemble the human idiopathic non‐cirrhotic portal hypertension syndrome. We correlated the presence of portal remodelling with a higher expression of protein and mRNA levels of TGFβ and BMP7, a key regulator of the TGFβ‐dependent endothelial‐to‐mesenchymal transition.

Conclusion

These data demonstrate that HNF4α does not play a major role during β‐catenin‐driven HCC, thus revealing that the tumour suppressor role of HNF4α is far more complex and dependent probably on its temporal expression and tumour context. However, HNF4α loss in adult hepatocytes could induce abnormal portal structures resembling the human idiopathic non‐cirrhotic portal hypertension syndrome, which may result from endothelial‐ and epithelial‐to‐mesenchymal transitions.
Postglacial ecotype formation under outcrossing and self‐fertilization inArabidopsis lyrata
Authors: Lucek Kay , Hohmann Nora , Willi Yvonne
Published: February 2019

The formation of ecotypes has been invoked as an important driver of postglacial biodiversity, because many species colonized heterogeneous habitats and experienced divergent selection. Ecotype formation has been predominantly studied in outcrossing taxa, while far less attention has been paid to the implications of mating system shifts. Here, we addressed whether substrate‐related ecotypes exist in selfing and outcrossing populations ofArabidopsis lyratasubsp.lyrataand whether the genomic footprint differs between mating systems. The North American subspecies colonized both rocky and sandy habitats during postglacial range expansion and shifted the mating system from predominantly outcrossing to predominantly selfing in a number of regions. We performed an association study on pooled whole‐genome sequence data of 20 selfing or outcrossing populations, which suggested genes involved in adaptation to substrate. Motivated by enriched gene ontology terms, we compared root growth between plants from the two substrates in a common environment and found that plants originating from sand grew roots faster and produced more side roots, independent of mating system. Furthermore, single nucleotide polymorphisms associated with substrate‐related ecotypes were more clustered among selfing populations. Our study provides evidence for substrate‐related ecotypes inA. lyrataand divergence in the genomic footprint between mating systems. The latter is the likely result of selfing populations having experienced divergent selection on larger genomic regions due to higher genome‐wide linkage disequilibrium.
Deciphering the essentiality and function of the anti‐σM factors in Bacillus subtilis
Authors: Zhao Heng , Roistacher Daniel M. , Helmann John D.
Published: February 2019

Bacteria use alternative sigma factors to adapt to different growth and stress conditions. The Bacillus subtilis extracytoplasmic function sigma factor SigM regulates genes for cell wall synthesis and is crucial for maintaining cell wall homeostasis under stress conditions. The activity of SigM is regulated by its anti‐sigma factor, YhdL, and the accessory protein YhdK. Here, we show that dysregulation of SigM caused by the absence of either component of the anti‐sigma factor complex leads to toxic levels of SigM and severe growth defects. High SigM activity results from a dysregulated positive feedback loop, and can be suppressed by overexpression of the housekeeping sigma, SigA. Using a sigM merodiploid strain, we selected for suppressor mutations that allow survival of yhdL depletion strain. The recovered suppressor mutations map to the beta and beta‐prime subunits of RNA polymerase core enzyme and selectively reduce SigM activity, and in some cases increase the activity of other alternative sigma factors. This work highlights the ability of mutations in RNA polymerase that remodel the sigma‐core interface to differentially affect sigma factor activity, and thereby alter the transcriptional landscape of the cell.
‘Like a human being, I was an equal, I wasn't just a patient’: Service users’ perspectives on their experiences of relationships with staff in mental health services
Authors: Bacha Karin , Hanley Terry , Winter Laura Anne
Published: February 2019

Objectives

The quality of therapeutic relationships in psychiatric services has a significant impact upon the therapeutic outcomes for people diagnosed with a severe mental illness. As previous work has not explicitly explored service users’ in‐depth views about the emotional impact of these relationships, the objective of this work was to bring this perspective to the fore and to gain a greater understanding about which relational components can lead to psychological change.

Design

The project was conducted alongside a service user organization. An interview design was used to qualitatively explore service users’ experiences and perceptions of their relationships with mental health practitioners.

Methods

Eight individuals who had experience of the mental health system in the United Kingdom were interviewed. Interpretative phenomenological analysis was used to analyse the data.

Findings

Three superordinate themes emerged from the analysis. These were (1) Trying to survive: am I a person or just an object in the system?; (2) Traumatic experiences within relationships; and (3) Helpful and transformative relationships. Further, the key transformative components of these relationships were power, safety, and identity.

Conclusions

Mental health services should be more focused upon care, rather than control. The Power Safety Identity (PSI) model, a reflexive model based upon key relational components highlighted by participants, is proposed for services and professionals to consider their work. The components of this model are managed by mental health practitioners and can determine whether these relationships maintain, increase, or alleviate psychological distress.

Practitioner points

Awareness of the relational components of power, safety, and identity has the potential to help practitioners reflect upon the tensions they experience in their relationships with service users.

Mental health services and professionals that are sensitive to issues related to power, safety, and identity when responding to the needs of the service users can improve how individuals perceive the quality of care provided by them.

Relationships between service users and mental health practitioners can encourage recovery if they are consistent, safe, trusting, provide protective power, and mirror a positive sense of self.
Cytokine secretion and the risk of depression development in patients with connective tissue diseases
Authors: Grygiel‐Górniak Bogna , Limphaibool Nattakarn , Puszczewicz Mariusz
Published: February 2019

Research in the past two decades has revolutionized our understanding of depressive illnesses. Proinflammatory cytokines have become a point of interest in the interconnecting areas of neuropsychiatric and autoimmune diseases. The cytokine hypothesis of depression suggests that pro‐inflammatory cytokines play a primary role in the mediation of the pathophysiological characteristics of major depression, in which an inflammatory process may be induced by external and internal stressors, such as psychological and inflammatory diseases, respectively. The higher prevalence of depression, particularly in patients with chronic autoimmune connective tissue disorders (CTD), suggests that depression may present a dysfunctional adaptation of cytokine‐induced sickness, which could manifest in times of an exacerbated activation of the innate immune system. Inflammation is thought to contribute to the development of clinical depression through its ability to induce sickness behaviors corresponding to the neurovegetative features of depression, through the dysregulation of the hypothalamic–pituitary–adrenal axis, alterations in neurotransmitter synthesis and reuptake, and through its involvement in the neuroprogression pathways. This review explores the complex interrelationships in which inflammatory responses alter neuroendocrine and neuropsychological regulation contributing to depressive symptoms in CTD. The prevalence and characteristics of depression, and its correlation to the levels of inflammatory cytokines and disease activity among different CTD will be reviewed.
Early post‐operative intravenous tacrolimus in pediatric liver transplant recipients is not superior to oral tacrolimus
Authors: Sabra Tarek Abdelazeem , Okajima Hideaki , Yoshizawa Atsushi , Ogawa Eri , Okamoto Shinya , Osman Mohamed Abdelkader , Saad‐Eldin Yasser , Uemoto Shinji
Published: February 2019

We aimed to compare the early results of i.v. with p.o. TAC as a primary immunosuppressant in pediatric patients undergoing LT. This retrospective study enrolled 75 children who underwent LT and received TAC‐steroid regimens as a primary immunosuppressant between September 2011 and October 2015 at our institution. Thirty‐five recipients received TAC i.v. and 40 received TAC p.o. Early results were evaluated and compared, including ACR, EBV, or CMV infection; renal adverse effects; and hospital stay. Comparisons of 90‐day post‐transplant results showed that the rates of overall viral (74% vs 40% P < 0.002), EBV (46% vs 17.5% P < 0.008), and CMV (51% vs 30% P = 0.05) infections were significantly higher in the i.v. than in the p.o. group. Neither regimen has any adverse effects on renal function. There were no between‐group differences in ACR incidence and severity, serum creatinine concentration, and hospital stay. Patient and graft survival rates at 3 months and 1 year did not differ significantly between the two groups. Compared with p.o. treatment, i.v. administration of high TAC concentration did not have beneficial post‐transplant effects on ACR incidence and severity, while increasing the incidence of viral infections in pediatric LT.
Indications and efficacy of conversion from tacrolimus‐ to sirolimus‐based immunosuppression in pediatric patients who underwent liver transplantation for unresectable hepatoblastoma
Authors: Hendrickson Richard J. , Sujka Joseph , Fischer Ryan , Manalang Michelle , Daniel James , Andrews Walter S.
Published: February 2019

SRL‐based immunosuppressive strategies in pediatric liver transplantation are not clearly defined, especially within the first year after liver transplant. TAC is the more common, traditional immunosuppressant used. However, SRL may modulate TAC‐associated kidney injury and may also have antiproliferative properties that are valuable in the management of patients following liver transplantation for HB. We sought to determine whether early conversion from TAC to SRL was safe, effective, and beneficial in a subset of liver transplant recipients with unresectable HB exposed to CDDP‐based chemotherapy. Between 2008 and 2013, six patients were transplanted for unresectable HB. All patients received at least one cycle of CDDP‐based chemotherapy prior to transplant. All patients were switched from TAC‐ to SRL‐based immunosuppression within 1 year of transplant. Five patients had improvement in their mGFR, while one patient had a slight decline. The improvement in mGFR was statistically significant. No adverse events were identified. Three patients had BPAR that responded to pulsed steroids. Historical controls showed similar rates of BPAR within the first year after transplant. There were no identified HB recurrences in the follow‐up time period. Conversion from TAC to SRL appears to be safe and effective in this selected group of pediatric liver transplant recipients without adverse reaction or HB recurrences.
Induction of tolerogenic properties by Anisakis larval antigens on murine dendritic cells
Authors: Zamora Vega , Rodero Marta , Andreu‐Ballester Juan Carlos , Mendez Susana , Cuéllar Carmen
Published: February 2019

Aims

The objective of this work is to investigate whether Anisakis simplex larval antigens present immunomodulatory properties by the induction of tolerogenic dendritic cells (DCs) from two strains of mice (BALB/c and C57BL/6J).

Methods and Results

We used mouse bone marrow‐derived DCs. We determined their antigen‐presenting ability by expression of membrane markers (MHC I and MHC II, CD80, CD86) and intracellular expression levels of IL‐10 and IL‐12 cytokines. We also analysed whether stimulation with A simplex larval antigens is enhanced by the co‐administration of the TLR4 and TLR9 agonists [LPS E coli 026B6 and CpG (ODN1826), respectively]. Two differential types of responses were found in the two mouse strains studied: the BALB/c strain showed an acute and inflammatory response, whereas the C57BL/6J mice developed a more discrete and resistant response. This suggests the coexistence of two opposing responses generated by A simplex larval antigens and confirms that the host genetic basis plays a role in the development of a Th2 or Treg response.

Conclusion

The study of the mechanisms by which Anisakis manipulates the immune response through anti‐inflammatory molecules is of interest not only for the direct application on the development of anthelmintic strategies, but also for the development of new anti‐inflammatory products.
Managing Patient Panels with Non‐Physician Providers
Authors: Bavafa Hessam , Savin Sergei , Terwiesch Christian
Published: February 2019

In recent years, the drive to contain health care costs has increased scrutiny of the traditional mode of delivering primary care where a patient is treated only by his primary care physician. In particular, greater reliance on non‐physician providers has been suggested as a lower‐cost alternative to the traditional set‐up. In this study, we consider a homogeneous patient panel treated by a solo primary care physician and develop a new model of patient health dynamics in which the health state for each patient on the physician’s panel follows Markovian transitions between “healthy,” “intermediate,” and “sick” states. In contrast to most currently used models, we treat patient demand for office visits as endogenous and managed by a physician via selection of a revisit frequency consistent with patient preferences. We model these preferences for the frequency of office visits using patients’ perception of their health status as well as the disutility associated with falling sick. At the center of our analysis are the interconnected decisions that a physician makes regarding the size of her patient panel and the patient revisit frequency. Our results quantify the overall impact of non‐physician providers on physician’s choices, physician’s expected daily compensation, and patients’ health. We characterize care settings, defined in terms of care effectiveness, characteristics of patient panel, as well as physician’s compensation scheme, that result in both parties, physician and patients, being better off as well as settings where at least one of the parties is worse off compared to the traditional approach.
Retail Price Competition with Product Fit Uncertainty and Assortment Selection
Authors: Sun Haoying , Gilbert Stephen M.
Published: February 2019

For many products, consumers need to physically experience them in order to assess their own valuations. We study how the equilibrium pricing among competing retailers depend upon assortments when consumers must search for this sort of fit information and are heterogeneous in their shopping behaviors. Specifically, we consider a market that consists of two retailers and two possible products. A consumer is either loyal to one of the retailers or is a shopper who follows a rational dynamic search process based on the prices and available assortments. We demonstrate how the retailers’ equilibrium pricing strategies depend upon their assortment choices and the resulting search process. Among other things, we show that, when the retailers carry non‐overlapping assortments, as search cost increases, the equilibrium pricing strategy changes from a low price with no discounting, to a high price with deep discounting. Furthermore, we find that when a full line retailer competes with a limited line retailer, a strategy of discounting only the common product can dominate one of discounting both products together. This is not the case when his rival also carries the full product line.
Infection risks for patients from healthcare workers with cystic fibrosis ‐ Reply
Authors: Bell Scott C. , Stuart Rhonda L.
Published: February 2019

See Letter
Stokes waves with constant vorticity: I. Numerical computation
Authors: Dyachenko Sergey A. , Hur Vera Mikyoung
Published: February 2019

Periodic traveling waves are numerically computed in a constant vorticity flow subject to the force of gravity. The Stokes wave problem is formulated via a conformal mapping as a nonlinear pseudodifferential equation, involving a periodic Hilbert transform for a strip, and solved by the Newton‐GMRES method. For strong positive vorticity, in the finite or infinite depth, overhanging profiles are found as the amplitude increases and tend to a touching wave, whose surface contacts itself at the trough line, enclosing an air bubble; numerical solutions become unphysical as the amplitude increases further and make a gap in the wave speed versus amplitude plane; another touching wave takes over and physical solutions follow along the fold in the wave speed versus amplitude plane until they ultimately tend to an extreme wave, which exhibits a corner at the crest. Touching waves connected to zero amplitude are found to approach the limiting Crapper wave as the strength of positive vorticity increases unboundedly, while touching waves connected to the extreme waves approach the rigid body rotation of a fluid disk.
Enterolithic folds in evaporites as microbially induced sedimentary structures: New model of formation and interpretation in the geological record
Authors: Escavy José I. , Herrero María J.
Published: February 2019

Enterolithic structures are stratigraphically localized folds in gypsum beds found in certain saline evaporitic sedimentary units in a wide variety of basins. Different models of formation have been proposed, all related to inorganic processes. These models include: diagenetic transformation of gypsum beds producing either displacive growth of crystals or volume changes; mechanical folding caused by compressional stress; and folding produced by slumping. The analysis of three Cenozoic evaporite sequences in Spain reveals that none of the previous models explains their origin and existence. In these outcrops, gypsum enterolithic structures occur in horizontal beds with parallel troughs and crests of the folds. They appear in shoreline facies of lacustrine environments and did not undergo major diagenetic transformations after the primary lithification of the original sediment. Based on these observations, together with the study of a modern analogue in Minorca, Spain, a new model is proposed for the genesis of enterolithic structures. This new model is based on the existence of a microbial mat exposed to brine concentration–dilution cycles and strong wind events. The high wind flow events enhanced folding of the microbial mat that became subaerially exposed and lithified due to subsequent evaporation. Therefore, the presence of enterolithic structures could be used as an indicator of shallow water environmental conditions subject to variations in brine concentration in areas with strong wind flow events. Previous studies of some evaporitic successions should be revisited, taking into account the proposed model, which would imply new depositional environment interpretations. At the same time, the proposed model could explain the existence of Kinneyia‐type structures, also known as wrinkle structures, formed beneath microbial mats in peritidal zones. Moreover, considering enterolithic structures as microbially induced sedimentary structures could be useful as evidence of microbial life in the ancient geological record and on other planets such as Mars.
Scalable statistical inference for averaged implicit stochastic gradient descent
Authors: Fang Yixin
Published: February 2019

Stochastic gradient descent (SGD) provides a scalable way to compute parameter estimates in applications involving large‐scale data or streaming data. As an alternative version, averaged implicit SGD (AI‐SGD) has been shown to be more stable and more efficient. Although the asymptotic properties of AI‐SGD have been well established, statistical inferences based on it such as interval estimation remain unexplored. The bootstrap method is not computationally feasible because it requires to repeatedly resample from the entire data set. In addition, the plug‐in method is not applicable when there is no explicit covariance matrix formula. In this paper, we propose a scalable statistical inference procedure, which can be used for conducting inferences based on the AI‐SGD estimator. The proposed procedure updates the AI‐SGD estimate as well as many randomly perturbed AI‐SGD estimates, upon the arrival of each observation. We derive some large‐sample theoretical properties of the proposed procedure and examine its performance via simulation studies.
Sequential Requisites Analysis: A New Method for Analyzing Sequential Relationships in Ordinal Data*
Authors: Lindenfors Patrik , Krusell Joshua , Lindberg Staffan I.
Published: February 2019

Objectives

This article presents a new method inspired by evolutionary biology for analyzing longer sequences of requisites for the emergence of particular outcome variables across numerous combinations of ordinal variables in social science analysis.

Methods

The approach is a sorting algorithm through repeated pairwise investigations of states in a set of variables and identifying what states in the variables occur before states in all other variables. We illustrate the proposed method by analyzing a set of variables from version 7.1 of the V‐Dem data set (Coppedge et al. 2017. Varieties of Democracy (V‐Dem) Project; Pemstein et al. 2017. University of Gothenburg, Varieties of Democracy Institute: Working Paper No. 21). With a large set of indicators measured over many years, the method makes it possible to identify and compare long, complex sequences across many variables.

Results

This affords an opportunity, for example, to disentangle the sequential requisites of failing and successful sequences in democratization, or if requisites are different during different time periods.

Conclusions

For policy purposes, this is instrumental: Which components of democracy occur earlier and which later? Which components of democracy are therefore the ideal targets for democracy promotion at different stages?
Cenozoic thermal history reconstruction of the Dongpu Sag, Bohai Bay Basin: Insights from apatite fission‐track thermochronology
Authors: Tang Xiaoyin , Zuo Yinhui , Kohn Barry , Li Yi , Huang Shaopeng
Published: February 2019

Knowledge of the thermal history of the onshore Dongpu Sag (DPS), Bohai Bay Basin is important for understanding its tectonic development within a broader regional context and for elucidating its poorly studied source‐rock maturation history. To unravel DPS time‐temperature development, apatite fission‐track data were acquired from eight sandstone samples in three deep wells. Thermal history modelling indicates continuous heating during the rifting stage (early Eocene to late Oligocene), followed by cooling attributed to tectonic uplift between ~27 and ~16 Ma, which resulted in the removal of ~1,400 to 1,800 m of section. Reheating occurred during the subsidence stage from middle Miocene until present. Unlike typical passive continental margin basins, the DPS experienced accelerated post‐rifting subsidence from ~5.8 Ma, which was especially marked since ~2.6 Ma. This phase was probably triggered by normal fault reactivation, in combination with a variation in the deep heat flow pattern.
Treatment of canine postoperative ocular hypertension with combined latanoprost 0.005% and atropine 1% ophthalmic solutions
Authors: de Linde Henriksen Michala , Lim Christine , Sharp Julia L.
Published: February 2019

Objective

To compare the effects of topical 0.005% latanoprost (L) vs combined 0.005% latanoprost and 1% atropine (LA) on control of postoperative ocular hypertension (POH), development of posterior synechiae formation, pupil size, and blindness after phacoemulsification surgery in dogs.

Animal studied

Dogs with postoperative ocular hypertension were included in the study: L‐group, latanoprost (eight dogs, 14 eyes) andLA‐group, latanoprost and atropine (nine dogs, 15 eyes).

Procedures

Complete ophthalmic examinations including tonometry were performed at 1, 7, and 21 days following phacoemulsification.

Results

No significant differences were found between the measured intraocular pressure (IOP) at days 1 and 7 postphacoemulsification surgery in the L‐group and theLA‐group (P = 0.26 [14.12 ± 1.76 mmHg vs 16.96 ± 1.68 mmHg] andP = 0.71 [15.45 ± 1.43 mmHg vs 16.20 ± 1.36 mmHg], respectively). No significant differences were found between pupil sizes at day 7 for the two groups (P = 0.25 [13.83% vs 24.77%]). No significant differences were found between odds of posterior synechiae formation at day 21 (P = 0.92) with a probability ± SEfor L‐group vsLA‐group at 0.27 ± 0.14 vs 0.25 ± 0.13. No significant differences were found in odds of postoperative blindness between groups (P = 0.58) with a probability ± SEof 0.21 ± 0.11 vs 0.13 ± 0.09, respectively for L andLA.

Conclusions

Combined topical latanoprost and atropine in dogs maintains normal postoperativeIOPs but does not seem to cause increased mydriasis compared to latanoprost alone.
Eye removal following parotid duct transposition surgery: A survey of current practice among veterinary ophthalmologists
Authors: Zimmer Jennifer L. , Diehl Kathryn A. , Myrna Kathern E.
Published: February 2019

Objective

Identify dogs that required removal of an eye that had previously undergone a parotid duct transposition (PDT) and secondly to characterize demographics, surgical technique, and outcomes associated with it.

Procedure

An online survey was distributed to American College of Veterinary Ophthalmologists (ACVO) and Veterinary Ophthalmology (VOPH) listservs asking members to report the breed, reason for eye removal, time between surgeries, surgical technique, complications, and additional therapy instituted for dogs requiring removal of an eye subsequent to PDT surgery.

Results

Sixteen dogs fit the inclusion criteria. Small breeds (<15 kg) made up 80% of the study population. Time between surgeries was <6 months (1/16), 6 to 12 months (7/16), and ≥1 year (8/16). Reasons for eye removal included: advancing corneal disease (6/16), discomfort (6/16), reaction to saliva (4/16), decreased saliva production (2/16), glaucoma (1/16), orbital neoplasia (1/16), and endophthalmitis (1/16). Surgical techniques included: transection of the parotid duct without ligation (2/16), ligation (9/16), and reversal of the PDT with reimplantation into the mouth (5/16). Complications reported were two dogs who underwent duct ligation experienced prolonged dilation of the duct that resolved with medical therapy (1/2) or without additional therapy (1/2).

Conclusion

Ligation of or reversal of the PDT with reimplantation into the mouth are appropriate adjunctive surgical techniques when removing an eye that previously underwent PDT surgery. Two dogs with nonfunctional PDT had complication‐free eye removal with transection without ligation. Prolonged dilation of the duct is possible after eye removal with duct ligation and may resolve with time or medical management.
Anterior segment parameters in normal dogs using the Pentacam®HR Scheimpflug system
Authors: Wolfel Allison E. , Pederson Samantha L. , Cleymaet Allison M. , Hess Ann M. , Freeman Kate S.
Published: February 2019

Objective

To describe and compare normative anterior segment parameters between canine age groups using the Pentacam®HR Scheimpflug camera (Pentacam).

Animals Studied

Thirty‐six sedated dogs (60 eyes) of varying ages and breeds were imaged with the Pentacam; only nondiseased anterior segments were included.

Procedures

Dogs were divided into three age groups: Group 1 (1‐5 years), Group 2 (6‐10 years), and Group 3 (11‐15 years). Values assessed included central corneal thickness (CCT), anterior and posterior corneal elevation (ACE/PCE), anterior and posterior corneal curvature metrics, corneal volume (CV), anterior and posterior corneal astigmatism (AA/PA), anterior chamber depth (ACD), anterior chamber volume (ACV), and anterior chamber angle (ACA). Tukey‐adjusted pairwise comparisons were performed.

Results

Overall CCT (mean ± SD) was 631.07 ± 59.91 µm. Central corneal thickness was 608.60 ± 48.63 µm for Group 1, 648.57 ± 51.06 µm for Group 2, and 635.37 ± 73.71 µm for Group 3. Anterior corneal elevation (ACE) measured 9.08 ± 0.58 mm, PCE measured 8.04 ± 0.50 mm, and CV was 58.13 ± 5.39 mm3. Astigmatism values were 1.34 ± 0.94 D for AA and 0.46 ± 0.44 D for PA. Anterior chamber values were 3.76 ± 0.56 mm for ACD, 383.68 ± 66.24 mm3for ACV, and 23.62 ± 29.33˚ for ACA. Significant differences were found between Groups 1 and 2 for CV (55.08 ± 4.08 mm3and 60.32 ± 4.19 mm3, respectively), (P = 0.02).

Conclusions

Corneal volume significantly increased between Group 1 and Group 2. Central corneal thickness increased from Group 1 to Group 3, but was not significant with the current sample size. There were no other differences between age groups.
Joint Formation and Mechanical Performance of Friction Self-Piercing Riveted Aluminum Alloy AA7075-T6 Joints
Authors: Ma Yun Wu , Li Yong Bing , Lin Zhong Qin
Published: February 2019

AA7xxx series aluminum alloys have great potentials in mass saving of vehicle bodies due to pretty high specific strength. However, the use of these high strength materials poses significant challenges to the traditional self-piercing riveting (SPR) process. To address this issue, a novel process, friction self-piercing riveting (F-SPR), was applied to join aluminum alloy AA7075-T6 sheets. The effects of the spindle speed and rivet feed rate on F-SPR joint cross section geometry evolution, riveting force, and energy input were investigated systematically. It was found that the rivet shank deformation, especially the buckling of the shank tip before penetrating through the top sheet, has significant influence on geometry and lap shear failure mode of the final joint. A medium rivet feed rate combined with a high spindle speed was prone to produce a defect-free joint with sound mechanical interlocking. F-SPR joints with the failure mode of rivet shear fracture were observed to have superior lap shear peak load and energy absorption over the joints with mechanical interlock failure. The optimized F-SPR joint in this study exhibited 67.6% and 13.9% greater lap shear peak load compared with SPR and refill friction stir spot welding joints, respectively, of the same sheets. This research provides a valuable reference for further understanding the F-SPR process.
Computational Fluid Dynamics Investigation of the Flow of Trailing Edge Cooling Slots
Authors: Jiang Y. , Gurram N. , Romero E. , Ireland P. T. , di Mare L.
Published: February 2019

Slot film cooling is a popular choice for trailing edge (TE) cooling in high pressure (HP) turbine blades because it can provide more uniform film coverage compared to discrete film cooling holes. The slot geometry consists of a cutback in the blade pressure side connected through rectangular openings to the internal coolant feed passage. The numerical simulation of this kind of film cooling flows is challenging due to the presence of flow interactions such as step flow separation, coolant-mainstream mixing, and heat transfer. The geometry under consideration is a cutback surface at the trailing edge of a constant cross-section aerofoil. The cutback surface is divided into three sections separated by narrow lands. The experiments are conducted in a high-speed cascade in Oxford Osney Thermo-Fluids Laboratory at Reynolds and Mach number distributions representative of engine conditions. The capability of computational fluid dynamics (CFD) methods to capture these flow phenomena is investigated in this paper. The isentropic Mach number and film effectiveness are compared between CFD and pressure sensitive paint (PSP) data. When compared with the steady k − ω shear stress transport (SST) method, scale adaptive simulation (SAS) can agree better with the measurement. Furthermore, the profiles of kinetic energy, production, and shear stress obtained by the steady and SAS methods are compared to identify the main source of inaccuracy in RANS simulations. The SAS method is better to capture the unsteady coolant–hot gas mixing and vortex shedding at the slot lip. The cross flow is found to affect the film significantly as it triggers flow separation near the lands and reduces the effectiveness. The film is nonsymmetric with respect to the half-span plane, and different flow features are present in each slot. The effect of mass flow ratio (MFR) on flow pattern and coolant distribution is also studied. The profiles of velocity, kinetic energy, and production of turbulent energy are compared among the slots in detail. The MFR not only affects the magnitude but also changes the sign of production.
A Refined JKR Model for Adhesion of a Rigid Sphere on a Soft Elastic Substrate
Authors: Zhang Lei , Ru C. Q.
Published: February 2019

Surface energy outside the contact zone, which is ignored in the classical Johnson–Kendall–Roberts (JKR) model, can play an essential role in adhesion mechanics of soft bodies. In this work, based on a simple elastic foundation model for a soft elastic half space with constant surface tension, an explicit expression for the change of surface energy outside the contact zone is proposed for a soft elastic substrate indented by a rigid sphere in terms of two JKR-type variables (δ, a), where a is the radius of the contact zone and δ is the indentation depth of the rigid sphere. The derived expression is added to the classical JKR model to achieve two explicit equations for the determination of the two JKR variables (δ, a). The results given by the present model are demonstrated with detailed comparison with known results reported in recent literature, which verified the validity and robust accuracy of the present method. In particular, the present model confirms that the change of surface energy of the substrate can play an essential role in micro/nanoscale contact of soft materials (defined by W/(E*R)≥0.1, where W is the adhesive energy, E* is the substrate elasticity, and R is the rigid sphere radius). The present model offers a simpler analytical method for adhesion mechanics of a rigid sphere on a soft elastic substrate when compared with several existing methods proposed in recent literature that request more substantial numerical calculations.
Translation of a Coated Rigid Spherical Inclusion in an Elastic Matrix: Exact Solution, and Implications for Mechanobiology
Authors: Chen Xin , Li Moxiao , Liu Shaobao , Liu Fusheng , Genin Guy M. , Xu Feng , Lu Tian Jian
Published: February 2019

The displacement of relatively rigid beads within a relatively compliant, elastic matrix can be used to measure the mechanical properties of the matrix. For example, in mechanobiological studies, magnetic or reflective beads can be displaced with a known external force to estimate the matrix modulus. Although such beads are generally rigid compared to the matrix, the material surrounding the beads typically differs from the matrix in one or two ways. The first case, as is common in mechanobiological experimentation, is the situation in which the bead must be coated with materials such as protein ligands that enable adhesion to the matrix. These layers typically differ in stiffness relative to the matrix material. The second case, common for uncoated beads, is the situation in which the beads disrupt the structure of the hydrogel or polymer, leading to a region of enhanced or reduced stiffness in the neighborhood of the bead. To address both cases, we developed the first analytical solution of the problem of translation of a coated, rigid spherical inclusion displaced within an isotropic elastic matrix by a remotely applied force. The solution is applicable to cases of arbitrary coating stiffness and size of the coating. We conclude by discussing applications of the solution to mechanobiology.
A Complete, Continuous, and Minimal Product of Exponentials-Based Model for Five-Axis Machine Tools Calibration With a Single Laser Tracker, an R-Test, or a Double Ball-Bar
Authors: Xu Peng , Cheung Benny C. F. , Li Bing
Published: February 2019

Calibration is an important way to improve and guarantee the accuracy of machine tools. This paper presents a systematic approach for position independent geometric errors (PIGEs) calibration of five-axis machine tools based on the product of exponentials (POE) formula. Instead of using 4 × 4 homogeneous transformation matrices (HTMs), it establishes the error model by transforming the 6 × 1 error vectors of rigid bodies between different frames resorting to 6 × 6 adjoint transformation matrices. A stable and efficient error model for the iterative identification of PIGEs should satisfy the requirements of completeness, continuity, and minimality. Since the POE-based error models for five-axis machine tools calibration are naturally complete and continuous, the key issue is to ensure the minimality by eliminating the redundant parameters. Three kinds of redundant parameters, which are caused by joint symmetry information, tool-workpiece metrology, and incomplete measuring data, are illustrated and explained in a geometrically intuitive way. Hence, a straightforward process is presented to select the complete and minimal set of PIGEs for five-axis machine tools. Based on the established unified and compact error Jacobian matrices, observability analyses which quantitatively describe the identification efficiency are conducted and compared for different kinds of tool tip deviations obtained from several commonly used measuring devices, including the laser tracker, R-test, and double ball-bar. Simulations are conducted on a five-axis machine tool to illustrate the application of the calibration model. The effectiveness of the model is also verified by experiments on a five-axis machine tool by using a double ball-bar.
Combined Effect of Thermal Anisotropy and Forced Convection on the Growth of Binary Alloy Equiaxed Dendrites
Authors: Jakhar Amman , Bhattacharya Anirban , Rath Prasenjith , Mahapatra Swarup Kumar
Published: February 2019

A numerical model has been developed to simulate the growth of an equaixed binary alloy dendrite under the combined effect of thermal anisotropy and forced convection. A semi implicit–explicit approach is used where the velocity and pressure fields are solved implicitly using the SIMPLER algorithm, while energy and species conservation equations are treated explicitly. The effect of thermal anisotropy present in the solid crystal is implemented by the addition of a departure source term in the conventional isotropic heat transfer based energy equation. The departure source represents the anisotropic part of the diffusive term in the isotropic heat transfer based energy equation. Simulations were performed to find the relative effect of convection strength and thermal anisotropy on the growth rate and morphology of a dendrite. Subsequently, parametric studies were conducted to investigate the effect of thermal anisotropy ratio, inlet flow velocity, undercooling temperature, and the relative strength of the thermal to mass diffusivity ratio by analyzing the variation of the equilibrium tip velocity of the top and left arms, the arm length ratio (ALR), and the equivalent grain radius. Based on simulations, a chart has been developed, which demarcates different regimes in which convection or thermal anisotropy is the most dominant factor influencing the dendrite growth rate. The model has also been extended to study the growth of multiple dendrites with random distribution and orientation. This can be useful for the simulation of microstructure evolution under the combined effect of convection and thermal anisotropy.
Prediction and Comparison of Shell Condensers With Straight or Helical Channels for Underwater Vehicles
Authors: Chen Peiyu , Xie Gongnan , Sunden Bengt
Published: February 2019

The shell condenser is one of the key components of underwater vehicles. To study its thermal performance and to design a more efficient structure, a computational model is generated to simulate condensation inside straight and helical channels. The model combines empirical correlations and a MATLAB-based iterative algorithm. The vapor quality is used as a sign of the degree of condensation. Three calculation models are compared, and the optimal model is verified by a comparison of simulated results and available experimental data. Several cases are designed to reveal the effects of various inlet conditions and the diameter-over-radius (Dh/R) ratio. The results show that the inlet temperature and mass rate significantly affect the flow and heat transfer in the condensation process, the heat transfer capabilities of the helical channels are much better than that of the straight channel, and both the heat transfer coefficient and total pressure drop increase with the decrease of Dh/R. This study may provide a useful reference for performance prediction and structural design of shell condensers used for underwater vehicles and may provide a relatively universal prediction model for condensation in channels.
Phase-Change Materials/HDPE Composite Filament: A First Step Toward Use With 3D Printing for Thermal Management Applications
Authors: Freeman Thomas B. , Spitzer David , Currier Patrick N. , Rollin Virginie , Boetcher Sandra K.S.
Published: February 2019

Phase-change materials (PCMs) are a useful alternative to more traditional methods of thermal management of various applications. PCMs are materials that absorb large amounts of latent heat and undergo solid-to-liquid phase change at near-constant temperature. The goal of the research is to experimentally investigate the thermal properties of a novel shape-stabilized PCM/HDPE composite extruded filament. The extruded filament can then be used in a 3D printer for custom PCM/HDPE shapes. The PCM used in the study is PureTemp PCM 42, which is an organic-based material that melts around 42 °C. Four PCM/HDPE mixtures were investigated (all percentages by mass): 20/80, 30/70, 40/60, and 50/50. Preliminary findings include differential scanning calorimeter (DSC) measurements of melting temperature and latent heat as well as scanning electron microscope (SEM) pictures of filament composition.