bluuebunny/crossref_metadata_2025 huggingface dataset:
Inactivation of the PBRM1 tumor suppressor gene amplifies the HIF-response in VHL
−/−
clear cell renal carcinoma
Authors: Gao Wenhua , Li Wei , Xiao Tengfei , Liu Xiaole Shirley , Kaelin William G.
Published: January 2017

Significance

Mutational inactivation of the
VHL
tumor suppressor gene is the signature lesion in the most common form of kidney cancer and causes inappropriate accumulation of the HIF transcription factor, which activates genes that normally facilitate adaptation to hypoxia but, in the context of kidney cancer, also promote tumorigenesis. Additional mutational events are needed, in conjunction with VHL loss, to cause kidney cancer. The most common of these are inactivating mutations of the PBRM1 tumor suppressor gene, which encodes a component [BRG1-associated factor 180 (BAF180)] of a multiprotein complex [Polybromo- and BRG1-associated factors-containing complex (PBAF)] that regulates the positions of nucleosomes throughout the genome. We describe here kidney cancer cell-based models for monitoring BAF180 function and show that loss of BAF180 accentuates the transcriptional response to HIF.
Case in Heritage Korean
Authors: Kim Kitaek , O’Grady William , Schwartz Bonnie D.
Published: January 2017

In a series of five experiments with 31 Korean heritage children, we show that knowledge of case and the ability to use it must be evaluated with careful attention to multiple factors that can influence access to morphological information in the course of comprehension and production. The first two experiments, which compared the canonical SOV pattern with the non-canonical OSV pattern, employed picture-selection comprehension tasks to assess knowledge of case. Poor performance on OSV sentences was mitigated by experimental manipulations that either enhanced the perceptual salience of case or provided felicitous conditions for the use of non-canonical word order. The next three experiments, all involving production tasks, revealed that many children who failed to demonstrate knowledge of case in the comprehension tasks actually produced nominative and accusative case correctly, thereby revealing their knowledge of this morphosyntactic system.
On subadditivity of Kodaira dimension in positive characteristic over a general type base
Authors: Patakfalvi Zsolt
Published: January 2017

We show that for a surjective, separable morphism

f
f

of smooth projective varieties over a field of positive characteristic such that

f
∗

O

X

≅

O

Y

f_* \mathcal {O}_X \cong \mathcal {O}_Y

subadditivity of Kodaira dimension holds, provided the base is of general type and the Hasse-Witt matrix of the geometric general fiber is not nilpotent.
BRUCH MEMBRANE AND THE MECHANISM OF MYOPIZATION
Authors: Jonas Jost B. , Ohno-Matsui Kyoko , Jiang Wen Jun , Panda-Jonas Songhomitra
Published: January 2017

Background:

The process of emmetropization is the adjustment of the length of the optical axis to the given optical properties of the cornea and lens after the end of the second year of life. Since its underlying mechanisms have not been fully explored yet, we reviewed findings available in the literature to discuss its potential etiology and the mechanism of myopization as an overshooting of emmetropization.

Methods:

Literature review.

Results:

The process of emmetropization occurs by axial elongation. Up to the end of the second year of life, the eye grows spherically by active increase in scleral volume. Axial elongation in the process of emmetropization is associated with thinning of the retina and reduced density of retinal pigment epithelium cells (RPE) in the retro-equatorial region, and with thinning more of the choroid than of the sclera, starting at the equator and being most marked at the posterior pole. In contrast, retinal thickness and RPE density in the macular region and thickness of Bruch's membrane (BM) in any region are independent of axial length.

Conclusions:

It led to the hypothesis that axial elongation occurs by production of BM in the retro-equatorial region leading to a decreased RPE density and retinal thinning in that region and a more tube-like than spherical enlargement of the globe, without compromise in the density of the macular RPE cells and in macular retinal thickness. The increased disc-fovea distance in axially myopic eyes is caused by the development and enlargement of parapapillary, BM free, gamma zone while the length of macular BM, and indirectly macular RPE cell density and macular retinal thickness, remain constant. The target tissue for medical modification of emmetropization/myopization may be the RPE, producing and elongating BM in the retro-equatorial region.
OUTER RETINAL TUBULATIONS IN CHRONIC RHEGMATOGENOUS RETINAL DETACHMENT
Authors: Seidman Carly , Kiss Szilard , Orlin Anton
Published: January 2017

Background/Purpose:

To present the first reported case of outer retinal tubulations in the setting of a rhegmatogenous retinal detachment.

Methods:

Case report.

Patients:

A 56-year-old man presented with a right eye retinal detachment of unclear duration. On examination, he was found to have a chronic-appearing rhegmatogenous retinal detachment involving the peripheral macula with a demarcation line.

Results:

Spectral-domain optical coherence tomography revealed outer retinal tubulations in the area of demarcation but not in the area of the detached retina.

Conclusion:

Outer retinal tubulations have been described in a wide spectrum of retinal diseases. The authors herein present the first reported case of outer retinal tubulations in the setting of a rhegmatogenous retinal detachment which may further aid in describing their pathogenesis.
CENTRAL RETINAL ARTERY OCCLUSION WITH DOUBLE CILIORETINAL ARTERY SPARING
Authors: Doguizi Sibel , Sekeroglu Mehmet A. , Anayol Mustafa A. , Yilmazbas Pelin
Published: January 2017

Purpose:

To report a patient with central retinal artery occlusion with double cilioretinal artery sparing.

Methods:

Retrospective case report.

Results:

A 45-year-old woman presented with sudden vision loss in her left eye for 10 days. Her best-corrected visual acuity was counting fingers at 2 meters in the left eye and 20/20 in the right eye. Funduscopy showed retinal opacity of posterior fundus, most marked in the macular region, and two small areas of the normal retina; one temporal to the optic disk and the other superior to the optic disk corresponding to the patent cilioretinal retinal arteries in the left eye; the right eye was normal. Fundus fluorescein angiography showed rapid filling of the two cilioretinal vessels and delayed filling of the central retinal artery at initial and last visits. Spectral domain optical coherence tomography findings disclosed diffuse thickening of the neurosensory retina in the perifoveolar area except two small areas at the first visit. After 6 months, spectral domain optical coherence tomography revealed diffuse thinning of the neurosensory retina except two small areas of the retina fed from two patent cilioretinal arteries.

Conclusion:

In this report, we documented double cilioretinal artery sparing in a patient with central retinal artery occlusion. It seems that a second cilioretinal artery can be present in some patients with central retinal artery occlusion.
NEW FINDINGS FROM MULTIMODAL FUNDUS IMAGING OVER 3 YEARS OF A PATIENT WITH MICROCEPHALY, CHORIORETINOPATHY, AND KIF11 MUTATION
Authors: Rososinski Anthony , Tran Tuan , Galvin Justin , Patel Chirag , Fung Adrian T.
Published: January 2017

Purpose:

To describe ocular features and long-term follow-up in a patient with microcephaly, chorioretinopathy, and KIF11 mutation.

Methods:

Multimodal imaging including fundus color photography, autofluorescence, spectral-domain optical coherence tomography, visual fields, electrophysiologic assessment, and neuroimaging.

Results:

A 44-year-old man with microcephaly and long-standing poor vision in his right eye presented for general ophthalmic review. Fundus examination revealed bilateral, symmetrical, inferior, atrophic chorioretinal lacunae, outer retinal and retinal pigment epithelial atrophy, curvilinear streaks, and retinal arteriolar sheathing. These findings were documented over a 3-year period by multimodal imaging and showed slow progressive deterioration in visual acuity, visual field testing, and fundus autofluorescence appearance. Genetic testing confirmed a KIF11 gene mutation.

Conclusion:

Curvilinear streaks and retinal arteriolar sheathing in this patient expand on the more typical fundus findings of KIF11 mutations. The outer retina is preferentially involved, and there is anatomical sparing of the macula until later in the disease state when multifocal electroretinography indicates functional impairment. Lacunae represent scleral depressions with the loss of overlying choroid and outer retina. Slow atrophic progression with loss of vision may occur over time.
Patients unfit for neoadjuvant therapy may still undergo resection of locally advanced esophageal or esophagogastric junctional cancer with acceptable oncological results
Authors: O’Neill J. Robert , Kennedy Ewan D. , Save Vicki , Langdale-Brown Barbara , Wall Lucy , Skipworth Richard J.E. , Paterson-Brown Simon
Published: January 2017

Introduction:

Neoadjuvant chemotherapy (NA) is routinely offered to patients undergoing resection for locally advanced (≥cT3Nx or cTxN+) esophageal or esophagogastric junctional (EGJ) cancer in the United Kingdom. Patients with comorbidity precluding the use of NA can be considered for resection yet the effect of omitting NA on survival is unclear.

Methods:

Retrospective review of prospectively collected clinical data from patients undergoing attempted curative therapy for ≥cT3Nx or cTxN+ esophageal or EGJ (Siewert type I-III) cancer between 2001 and 2013.

Results:

NA was commenced in 289 patients and primarily comprised 2 cycles of cisplatin and 5-fluorouracil (264 patients, 91%). Surgery alone was planned for 82 patients with NA omitted due to comorbidity. Patients undergoing surgery alone were matched for clinical variables and stage with those undergoing NA but were significantly older (mean=8 y, P<0.001). NA was associated with an improved median overall survival of 28.7 months, compared with 20.9 months for patients undergoing surgery alone (P=0.008). Patients undergoing surgery alone had a 90-day postoperative mortality rate of 10% compared with 3% for those undergoing NA (P=0.011). In patients discharged postoperatively, the median overall survival benefit of NA was 2.7 months (P=0.048). Those 19% of patients experiencing a significant histologic response to NA demonstrated further improved survival.

Conclusions:

NA improves survival in patients undergoing resection for locally advanced esophageal or EGJ cancer; however, the median benefit is <3 months in patients discharged postoperatively. Patients precluded from NA achieve acceptable oncological results but experience a higher risk of perioperative mortality.
A Novel Robotic Bilateral Internal Mammary Artery Harvest Using Double Docking Technique for Coronary Artery Bypass Grafting
Authors: Tarui Tatsuya , Ishikawa Norihiko , Watanabe Go
Published: January 2017

da Vinci Surgical System (da Vinci) enabled port access for internal mammary arteries (IMA) harvesting. However, bilateral IMA (BIMA) harvesting is difficult when performed on single side. We developed a novel technique of double docking the da Vinci by transpositioning from the left side to the right and examined the feasibility. Twelve patients underwent BIMA harvesting using the double-docking technique. First, the da Vinci was set on the patient's left side for the right IMA harvesting. Afterward, the da Vinci was undocked and transpositioned from the patient's left side to the right side. The time elapsed during rotation was measured. Subsequently, the left IMA was harvested from patient's right side. Distal anastomoses were performed by a small anterolateral thoracotomy. All of the IMAs were harvested and then bypassed without damage. The mean ± SD time that elapsed during rotation was 6.5 ± 0.6 minutes. There was no conversion to sternotomy. Bilateral IMA harvesting by the bilateral docking technique was performed successfully with acceptable feasibility.
Microbiota-targeted therapies on the intensive care unit
Authors: Haak Bastiaan W. , Levi Marcel , Wiersinga W. Joost
Published: January 2017

Purpose of review

The composition and diversity of the microbiota of the human gut, skin, and several other sites is severely deranged in critically ill patients on the ICU, and it is likely that these disruptions can negatively affect outcome. We here review new and ongoing studies that investigate the use of microbiota-targeted therapeutics in the ICU, and provide recommendations for future research.

Recent findings

Practically every intervention in the ICU as well as the physiological effects of critical illness itself can have a profound impact on the gut microbiota. Therapeutic modulation of the microbiota, aimed at restoring the balance between ‘pathogenic’ and ‘health-promoting’ microbes is therefore of significant interest. Probiotics have shown to be effective in the treatment of ventilator-associated pneumonia, and the first fecal microbiota transplantations have recently been safely and successfully performed in the ICU. However, all-encompassing data in this vulnerable patient group remain sparse, and only a handful of novel studies that study microbiota-targeted therapies in the ICU are currently ongoing.

Enormous strides have been made in characterizing the gut microbiome of critically ill patients in the ICU, and an increasing amount of preclinical data reveals the huge potential of microbiota-targeted therapies. Further understanding of the causes and consequences of dysbiosis on ICU-related outcomes are warranted to push the field forward.
Incidence of Occult Intrahepatic Metastasis in Hepatocellular Carcinoma Treated With Transplantation Corresponds to Early Recurrence Rates After Partial Hepatectomy
Authors: Aufhauser David D. , Sadot Eran , Murken Douglas R. , Eddinger Kevin , Hoteit Maarouf , Abt Peter L. , Goldberg David S. , DeMatteo Ronald P. , Levine Matthew H.
Published: January 2017

Objective:

This study aimed to compare the incidence of radiologically unrecognized (occult) hepatocellular carcinoma (HCC) lesions in explant hepatectomy specimens from orthotopic liver transplants (OLTs) performed for HCC with rates of HCC intrahepatic recurrence after resection.

Summary of Background Data:

Resection of HCC is associated with high rates of intrahepatic HCC recurrence. However, it is unclear whether these recurrences represent incomplete resection of unrecognized metastatic lesions from the primary tumor or subsequent de novo tumor formation due to inherent biological proclivity for HCC formation.

Methods:

We collected patient, tumor, and pathology data on HCC patients treated surgically from 3696 OLTs in the Organ Procurement and Transplantation (OPTN) national database, 299 OLTs at a single transplant center, and 232 partial hepatectomies from a hepatobiliary cancer center.

Results:

In the OPTN and high-volume transplant center cohorts, 37% and 42% of patients had occult HCC lesions on explant pathology, respectively. Among cancer center patients, the 2-year recurrence rate was 46%, and 74% of patients who recurred presented with liver only recurrence.

Conclusion:

Although the transplant and resection populations differ, occult multifocality is common in transplant explants and similar to the 46% early recurrence rate following partial hepatectomy. These data suggest that noncurative resection often results from occult intrahepatic multifocality present at the time of resection rather than a malignant predisposition of the remnant liver with de novo tumorigenesis.
DeeperBind: Enhancing Prediction of Sequence Specificities of DNA Binding Proteins
Authors: Hassanzadeh Hamid Reza , Wang May D.
Published: January 2017

Transcription factors (TFs) are macromolecules that bind tocis-regulatory specific sub-regions of DNA promoters and initiate transcription. Finding the exact location of these binding sites (aka motifs) is important in a variety of domains such as drug design and development. To address this need, severalin vivoandin vitrotechniques have been developed so far that try to characterize and predict the binding specificity of a protein to different DNA loci. The major problem with these techniques is that they are not accurate enough in prediction of the binding affinity and characterization of the corresponding motifs. As a result, downstream analysis is required to uncover the locations where proteins of interest bind. Here, we propose DeeperBind, a long short term recurrent convolutional network for prediction of protein binding specificities with respect to DNA probes. DeeperBind can model the positional dynamics of probe sequences and hence reckons with the contributions made by individual sub-regions in DNA sequences, in an effective way. Moreover, it can be trained and tested on datasets containing varying-length sequences. We apply our pipeline to the datasets derived from protein binding microarrays (PBMs), an in-vitro high-throughput technology for quantification of protein-DNA binding preferences, and present promising results. To the best of our knowledge, this is the most accurate pipeline that can predict binding specificities of DNA sequences from the data produced by high-throughput technologies through utilization of the power of deep learning for feature generation and positional dynamics modeling.
Whole genome and RNA sequencing of 1,220 cancers reveals hundreds of genes deregulated by rearrangement of cis-regulatory elements
Authors: Zhang Yiqun , Chen Fengju , Fonseca Nuno A. , He Yao , Fujita Masashi , Nakagawa Hidewaki , Zhang Zemin , Brazma Alvis , Creighton Chad J. ,   on behalf of the PCAWG Transcriptome Working Group, PCAWG Structural Variation Working Group,   ICGC/TCGA Pan-Cancer Analysis of Whole Genomes Network
Published: January 2017

Using a dataset of somatic Structural Variants (SVs) in cancers from 2658 patients—1220 with corresponding gene expression data—we identified hundreds of genes for which the nearby presence (within 100kb) of an SV breakpoint was associated with altered expression. For the vast majority of these genes, expression was increased rather than decreased with corresponding SV event. Well-known up-regulated cancer-associated genes impacted by this phenomenon includedTERT,MDM2,CDK4,ERBB2,CD274,PDCD1LG2, andIGF2. SVs upstream ofTERTinvolved ~3% of cancer cases and were most frequent in liver-biliary, melanoma, sarcoma, stomach, and kidney cancers. SVs associated with up-regulation of PD1 and PDL1 genes involved ~1% of non-amplified cases. For many genes, SVs were significantly associated with either increased numbers or greater proximity of enhancer regulatory elements near the gene. DNA methylation near the gene promoter was often increased with nearby SV breakpoint, which may involve inactivation of repressor elements.

Abbreviations

PCAWG

the Pan-Cancer Analysis of Whole Genomes project

SV

Structural Variant
Toddlers later diagnosed with autism exhibit multiple structural abnormalities in temporal corpus callosum fibers
Authors: Fingher Noa , Dinstein Ilan , Ben-Shachar Michal , Haar Shlomi , Dale Anders M. , Eyler Lisa , Pierce Karen , Courchesne Eric
Published: January 2017

Interhemispheric functional connectivity abnormalities are often reported in autism and it is thus not surprising that structural defects of the corpus callosum (CC) are consistently found using both traditional MRI and DTI techniques. Past DTI studies however, have subdivided the CC into 2 or 3 segments without regard for where fibers may project to within the cortex, thus placing limitations on our ability to understand the nature, timing and neurobehavioral impact of early CC abnormalities in autism. Leveraging a unique cohort of 97 toddlers (68 autism; 29 typical) we utilized a novel technique that identified seven CC tracts according to their cortical projections. Results revealed that younger (<2.5 years old), but not older toddlers with autism exhibited abnormally low mean, radial, and axial diffusivity values in the CC tracts connecting the occipital lobes and the temporal lobes. Fractional anisotropy and the cross sectional area of the temporal CC tract were significantly larger in young toddlers with autism. These findings indicate that water diffusion is more restricted and unidirectional in the temporal CC tract of young toddlers who develop autism. Such results may be explained by a potential overabundance of small caliber axons generated by excessive prenatal neural proliferation as proposed by previous genetic, animal model, and postmortem studies of autism. Furthermore, early diffusion measures in the temporal CC tract of the young toddlers were correlated with outcome measures of autism severity at later ages. These findings regarding the potential nature, timing, and location of early CC abnormalities in autism add to accumulating evidence, which suggests that altered inter-hemispheric connectivity, particularly across the temporal lobes, is a hallmark of the disorder.
Evaluation of Oxford Nanopore MinIONTMSequencing for 16S rRNA Microbiome Characterization
Authors: Ma Xiao , Stachler Elyse , Bibby Kyle
Published: January 2017

In this manuscript we evaluate the potential for microbiome characterization by sequencing of near-full length 16S rRNA gene region fragments using the Oxford Nanopore MinION (hereafter ‘Nanopore’) sequencing platform. We analyzed pure-cultureE. coliandP. fluorescens, as well as a low-diversity mixed community sample from hydraulic fracturing produced water. Both closed and open reference operational taxonomic unit (OTU) picking failed, necessitating the direct use of sequences without OTU picking. The Ribosomal Database Project classifier against the Green Genes database was found to be the optimal annotation approach, with average pure-culture annotation accuracies of 93.8% and 82.0% at the phyla and genus levels, respectively. Comparative analysis of an environmental sample using Nanopore and Illumina MiSeq sequencing identified high taxonomic similarity when using a weighted metric (Bray-Curtis), and significantly reduced similarity when using an unweighted metric (Jaccard). These results highlight the great potential of Nanopore sequencing to analyze broad microbial community trends, and the challenge of applying Nanopore sequencing to discern rare taxa in mixed microbial communities. Finally, we observed that between-run carryover following washes on the same flowcell accounted for >10% of sequence reads, necessitating future development to either prevent carryover or filter sequences of interest (e.g. barcoding).
Distributed Biotin-Streptavidin Transcription Roadblocks for Mapping Cotranscriptional RNA Folding
Authors: Strobel Eric J. , Watters Kyle E. , Lucks Julius B.
Published: January 2017

RNA molecules fold cotranscriptionally as they emerge from RNA polymerase. Cotranscriptional folding is an important process for proper RNA structure formation as the order of folding can determine an RNA molecule’s structure, and thus its functional properties. Despite its fundamental importance, the experimental study of RNA cotranscriptional folding has been limited by the lack of easily approachable methods that can interrogate nascent RNA structures at nucleotide resolution during transcription. We previously developed cotranscriptional selective 2’-hydroxyl acylation analyzed by primer extension sequencing (SHAPE-seq) to simultaneously probe all of the intermediate structures an RNA molecule transitions through during transcription elongation. Here, we improve the broad applicability of cotranscriptional SHAPE-Seq by developing a sequence-independent streptavidin roadblocking strategy to simplify the preparation of roadblocking transcription templates. We determine the fundamental properties of streptavidin roadblocks and show that randomly distributed streptavidin roadblocks can be used in cotranscriptional SHAPE-Seq experiments to measure theBacillus cereus crcBfluoride riboswitch folding pathway. Comparison of EcoRIE111Qand streptavidin roadblocks in cotranscriptional SHAPE-Seq data shows that both strategies identify the same RNA structural transitions related to the riboswitch decision-making process. Finally, we propose guidelines to leverage the complementary strengths of each transcription roadblock for use in studying cotranscriptional folding.
Functional genomics reveals that tumors with activating phosphoinositide 3-kinase mutations are dependent on accelerated protein turnover
Authors: Davoli Teresa , Mengwasser Kristen E. , Duan Jingjing , Chen Ting , Christensen Camilla , Wooten Eric C. , Anselmo Anthony N. , Li Mamie Z. , Wong Kwok-Kin , Kahle Kristopher T. , Elledge Stephen J.
Published: January 2017

Activating mutations in the phosphoinositide 3-kinase (PI3K) signaling pathway are frequently identified in cancer. To identify pathways that support PI3K oncogenesis, we performed a genome-wide RNAi screen in isogenic cell lines harboring wild-type or mutant PIK3CA to search for PI3K synthetic-lethal (SL) genes. A combined analysis of these results with a meta-analysis of two other large-scale RNAi screening data sets in PI3K mutant cancer cell lines converged on ribosomal protein translation and proteasomal protein degradation as critical nononcogene dependencies for PI3K-driven tumors. Genetic or pharmacologic inhibition of either pathway alone, but not together, selectively killed PI3K mutant tumor cells in an mTOR-dependent manner. The expression of ribosomal and proteasomal components was significantly up-regulated in primary human colorectal tumors harboring PI3K pathway activation. Importantly, a PI3K SL gene signature containing the top hits of the SL genes identified in our meta-analysis robustly predicted overall patient survival in colorectal cancer, especially among patients with tumors with an activated PI3K pathway. These results suggest that disruption of protein turnover homeostasis via ribosome or proteasome inhibition may be a novel treatment strategy for PI3K mutant human tumors.
PDX1 dynamically regulates pancreatic ductal adenocarcinoma initiation and maintenance
Authors: Roy Nilotpal , Takeuchi Kenneth K. , Ruggeri Jeanine M. , Bailey Peter , Chang David , Li Joey , Leonhardt Laura , Puri Sapna , Hoffman Megan T. , Gao Shan , Halbrook Christopher J. , Song Yan , Ljungman Mats , Malik Shivani , Wright Christopher V.E. , Dawson David W. , Biankin Andrew V. , Hebrok Matthias , Crawford Howard C.
Published: January 2017

Aberrant activation of embryonic signaling pathways is frequent in pancreatic ductal adenocarcinoma (PDA), making developmental regulators therapeutically attractive. Here we demonstrate diverse functions for pancreatic and duodenal homeobox 1 (PDX1), a transcription factor indispensable for pancreas development, in the progression from normal exocrine cells to metastatic PDA. We identify a critical role for PDX1 in maintaining acinar cell identity, thus resisting the formation of pancreatic intraepithelial neoplasia (PanIN)-derived PDA. Upon neoplastic transformation, the role of PDX1 changes from tumor-suppressive to oncogenic. Interestingly, subsets of malignant cells lose PDX1 expression while undergoing epithelial-to-mesenchymal transition (EMT), and PDX1 loss is associated with poor outcome. This stage-specific functionality arises from profound shifts in PDX1 chromatin occupancy from acinar cells to PDA. In summary, we report distinct roles of PDX1 at different stages of PDA, suggesting that therapeutic approaches against this potential target need to account for its changing functions at different stages of carcinogenesis. These findings provide insight into the complexity of PDA pathogenesis and advocate a rigorous investigation of therapeutically tractable targets at distinct phases of PDA development and progression.
Hovering stability of a model helicopter
Authors: Murat Koc Ilker , Franko Semuel , Ozsoy Can
Published: January 2017

Purpose

The purpose of this paper is to investigate the stability of a small scale six-degree-of-freedom nonlinear helicopter model at translator velocities and angular displacements while it is transiting to hover with different initial conditions.

Design/methodology/approach

In this study, model predictive controller and linear quadratic regulator are designed and compared within each other for the stabilization of the open loop unstable nonlinear helicopter model.

Findings

This study shows that the helicopter is able to reach to the desired target with good robustness, low control effort and small steady-state error under disturbances such as parameter uncertainties, mistuned controller.

Originality/value

The purpose of using model predictive control for three axes of the autopilot is to decrease the control effort and to make the close-loop system insensitive against modeling uncertainties.
Tuning of controller for an aircraft flight control system based on particle swarm optimization
Authors: Kiyak Emre
Published: January 2017

Purpose

This study aims to present a method for the conceptual design and simulation of an aircraft flight control system.

Design/methodology/approach

The design methodology is based on particle swarm optimization (PSO). PSO can be used to improve the performance of conventional controllers. The aim of the present study is threefold. First, it attempts to detect and isolate faults in an aircraft model. Second, it is to design a proportional (P) controller, a proportional derivative (PD) controller, a proportional-integral (PI) controller and a fuzzy controller for an aircraft model. Third, it is to design a PD controller for an aircraft using a PSO algorithm.

Findings

Conventional controllers, an intelligent controller and a PD controller-based PSO were investigated for flight control. It was seen that the P controller, the PI controller and the PD controller-based PSO caused overshoot. These overshoots were 18.5, 87.7 and 2.6 per cent, respectively. Overshoot was not seen using the PD controller or fuzzy controller. Steady state errors were almost zero for all controllers. The PD controller had the best settling time. The fuzzy controller was second best. The PD controller-based PSO was the third best, but the result was close to the others.

Originality/value

This study shows the implementation of the present algorithm for a specified space mission and also for study regarding variation of performance parameters. This study shows fault detection and isolation procedures and also controller gain choice for a flight control system. A comparison between conventional controllers and PD-based PSO controllers is presented. In this study, sensor fault detection and isolation are carried out, and, also, root locus, time domain analysis and Routh–Hurwitz methods are used to find the conventional controller gains which differ from other studies. A fuzzy controller is created by the trial and error method. Integral of squared time multiplied by squared error is used as a performance function type in PSO.
Flight controller design for aircraft low altitude airdrop
Authors: Liu Ri , Sun Xiuxia , Dong Wenhan
Published: January 2017

Purpose

During low altitude airdrop operations, the heavy cargo moving inside and the sudden dropping out exert serious threats on the aircraft safety and mission performance. This paper aims to propose an efficient flight control method for the airdrop operations.

Design/methodology/approach

A novel controller which combines feedback linearization with nonlinear integral sliding mode control is proposed. The aircraft airdrop model is decoupled and linearized by using the feedback linearization technique. On this basis, an integral sliding mode controller is designed to stabilize the speed and pitch attitude of the aircraft. In the sliding manifold, one class of nonlinear functions with the property of “smaller errors correspond to bigger gains and bigger errors correspond to saturated gains” is introduced to form the integral term; thus, the overcompensation of the integral term to big errors is omitted, and the dynamic response performance is improved. Lyapunov-based stability analysis shows that the controller could completely reject model uncertainties by choosing proper controller parameters.

Findings

The flight control system with strong robustness could meet the low altitude airdrop indexes in the maximum weight cargo airdrop task.

Originality/value

This paper fulfils an urgent need to study how to control the aircraft to guarantee mission performance and flight safety during the low altitude airdrop operations.
Helicopter stabilizer optimization considering rotor downwash in forward-flight
Authors: Minervino Mauro , Vitagliano Pier Luigi , Quagliarella Domenico
Published: January 2017

Purpose

The paper aims to reduce the aerodynamic drag of a rotorcraft stabilizer in forward flight by taking into account downwash effects from the main rotor wake (power-on conditions).

Design/methodology/approach

A shape design methodology based on numerical optimization, CAD-in-the-loop (CAD: computer-aided design) approach and high-fidelity Computational Fluid Dynamics (CFD) tools was set-up and applied to modify the horizontal empennage of a rotorcraft configuration. This included the integration of both commercial and in-house computer-aided engineering tools for parametric geometry handling, adaptive mesh generation, CFD solution and evolutionary optimization within a robust evaluation chain for the aerodynamic simulation of the different design candidates generated during the automatic design loop. Geometrical modifications addressed both the stabilizer planform and sections, together with its setting angle in cruise configuration, accounting for impacts on the equilibrium, stability and control characteristics of the empennage.

Findings

An overall improvement of 11.1 per cent over the rotorcraft drag was estimated at the design condition (cruise flight; power-on) for the stabilizer configuration with optimized planform shape, which is increased to 11.4 per cent when combined with the redesigned airfoil to generate the stabilizer surface.

Research limitations/implications

Critical design considerations are introduced with regard to structural and systems integration issues, and a design candidate alternative is identified and proposed as a compromise solution, achieving 8.3 per cent reduction of the rotorcraft configuration drag in cruise conditions with limited increase in the empennage aspect ratio and leading edge sweep angle when compared to the pure aerodynamic optimal design obtained from genetic algorithm evolution.

Originality/value

The proposed methodology faces the empennage design problem by explicitly taking into account the effects of main rotor wake impinging the stabilizer surface in forward flight conditions and using an automated optimization approach which directly incorporates professional CAD tools in the design loop.
Fuzzy logic estimator implemented in observation-tracking device control
Authors: Sobolewski Michal , Grzesik Norbert , Koruba Zbigniew , Nowicki Michal
Published: January 2017

Purpose

Nowadays, various methods of observation from unmanned aerial vehicles (UAV) are being widely developed. There are many ways of increasing the amount of information retrieved from captured material. Unfortunately, hardware solutions consume a lot of energy, which is unacceptable in UAV applications, as it can have direct impact on the observing time on UAV. Those kinds of problems have been identified during the development phase of stabilizing platform in Polish Research Space Centre in Warsaw. As a result of that fact, energy saving control methods have been implemented, which estimates quality of stabilization process for the observation-tracking device (OTD).

Design/methodology/approach

Mathematical model has been designed and validated with real-life experiments for the purpose of optimization of stabilization and control process. Two types of controlling algorithms have been implemented: linear quadratic regulator and proportional derivative method for driving the mechanism. Based on numerical simulations of the mechanical model being controlled by the mentioned driver, it was possible to define membership functions. After the process of defuzzification, the controller predicts quality of stabilization under defined environmental working conditions.

Findings

An autonomous energy saving system has been created that can be implemented in many applications, where environmental conditions may change significantly.

Practical implications

To test the proposed fuzzy controller, OTD has been chosen as an example object of application. It is a mechanical platform which houses the optical observation system. It is designed to provide the best working conditions during flight.

Originality/value

That kind of decision-making unit has never been implemented before during observations which were carried out during flying of an object. That innovative controller should bring significant energy consumption savings.
Turbulent jet in crossflow analysis with LES approach
Authors: Tahani Mojtaba , Hojaji Mohammad , Mahmoodi Jezeh Seyed Vahid
Published: January 2017

Purpose

This study aims to investigate effects of sonic jet injection into supersonic cross-flow (JISC) numerically in different dynamic pressure ratio values and free stream Mach numbers.

Design/methodology/approach

Large Eddy simulation (LES) with dynamic Smagorinsky model is used as the turbulence approach. The numerical results are compared with the experimental data, and the comparison shows acceptable validation.

Findings

According to the results, the dynamic pressure ratio has critical effects on the zone related to barrel shock. Despite free stream Mach number, increasing dynamic pressure ratio leads to expansion of barrel shock zone. Consequently, expanded barrel shock zone would bring about more obstruction effect. In addition, the height of counter-rotating vortex pair increases, and the high-pressure area before jet and low-pressure area after jet will rise. The results show that the position of barrel shock is deviated by increasing free stream Mach number, and the Bow shock zone becomes stronger and close to barrel shock. Moreover, high pressure zone, which is located before the jet, decreases by high free stream Mach number.

Practical implications

In this study, LES with a dynamic Smagorinsky model is used as the turbulence approach. Effects of sonic JISC are investigated numerically in different dynamic pressure ratio values and free stream Mach numbers.

Originality/value

As summary, the following are the contribution of this paper in the field of JISC subjects: several case studies of jet condition have been performed. In all the cases, the flow at the nozzle exit is sonic, and the free stream static pressure is constant. To generate proper grid, a cut cell method is used for domain modelling. Boundary condition effect on the wall pressure distribution around the jet and velocity profiles, especially S shape profiles, is investigated. The results show that the relation between representing the location of Mach disk centre and at transonic regime is a function of second-order polynomial, whereas at supersonic regime, the relationship is modelled as a first-order polynomial. In addition, the numerical results are compared with the experimental data demonstrating acceptable validation.
Accounting academics’ teaching self-efficacy and ethics integration in accounting courses
Authors: Marzuki Marzlin , Subramaniam Nava , Cooper Barry J. , Dellaportas Steven
Published: January 2017

Purpose

The purpose of this paper is to examine the extent to which ethics education is incorporated in the curriculum by accounting academics (EXTENT) and its relationship with the following four factors: accounting academics’ attitudes towards ethics education (ATTDE); head of department support (HODS); peer support (PEERS); and accounting academics’ ethics teaching self-efficacy (ETSE).

Design/methodology/approach

The study utilises data from a questionnaire survey of 117 accounting academics in Malaysia and engages path analysis to test various hypothesised relationships.

Findings

The results indicate that ATTDE, HODS and PEERS have a significant and positive impact on accounting academics’ ETSE. The findings also suggest that ETSE and PEERS have a direct and positive impact on EXTENT. Overall, ETSE is found to be a significant mediating variable in the relationship between ATTDE, HODS, PEERS and EXTENT.

Research limitations/implications

The relatively small sample of 117 Malaysian accounting academics and the limited number of factors studied as drivers of ETSE, which limits generalisability of the results.

Practical implications

This paper is particularly useful for informing heads of departments and the regulatory and professional bodies of resourcing and fostering a work environment that supports peer support and interactions as well as knowledge resources that facilitate individual accounting academics’ to integrate ethics content in their courses or units.

Originality/value

The study is guided by Bandura’s (1977, 1997) self-efficacy theory and adapts Tschannen-Moran and Hoy’s (2001) teacher efficacy construct in understanding how accounting academic’s belief in one’s ability to complete tasks and achieve goals affects the level of integration of ethics in their courses.
An event study of the effects of regulatory changes on the food industry
Authors: Xiao Xingzhi , Gao Yue
Published: January 2017

Purpose

The purpose of this paper is to examine the effects of China’s Food Safety Law on its food industry.

Design/methodology/approach

First, an event study is employed to investigate the impact of regulatory changes on the food industry. Then the authors examine the association between the magnitude of cumulative abnormal returns (CARs) and firm characteristics in a cross-sectional regression framework.

Findings

The results suggest that the announcements of some important events during the legislative process do affect the investors’ expectations. Further analysis shows that some sub-industries, especially the dairy industry, underperform the others around the enforcement date of the Food Safety Law, indicating that investors expect more costs of compliance for the sub-industries with lower levels of food safety. Moreover, CARs are found to be positively correlated with firm size, implying that larger firms may benefit more from this food legislative reform than small ones.

Practical implications

Measuring the impact of regulatory changes on food producers and investors by stock market response could help regulators assess the effectiveness of regulation and amend the law accordingly.

Originality/value

Previous studies seldom empirically examine the effect of Food Safety Laws on China’s food industry and this study attempts to fill this gap, which contributes to extending the understanding of the impact of legislative reform or regulatory changes on related industries.
Food expenditure responses to income/expenditure shocks in rural China
Authors: Cui Qi , Huang Jikun
Published: January 2017

Purpose

The purpose of this paper is to examine the impacts of large income and expenditure shocks on household food expenditures and determines whether the impacts of large shocks differ among households, especially low-income households.

Design/methodology/approach

The study’s data are drawn from a household survey conducted in rural China. Multivariate analysis examines the impacts of large income and expenditure shocks on food expenditures.

Findings

The impacts of large positive income shocks on food expenditure are moderate. However, households reduce their per capita food expenditures within a range of about 25-30 percent after suffering large negative shocks. The greatest impact is found for shocks where expenditures more than double, followed by the impact of shocks where income declines by more than half. Moreover, food expenditures among low-income households are much more sensitive to large negative income and expenditure shocks. The paper concludes with policy implications.

Originality/value

This is the first Chinese study to empirically examine the impacts of different income and expenditure shocks on household food expenditures. The results have important implications for smoothing households’ food consumption after they suffer from shocks.
Income implications of political capital and agricultural land use in western China
Authors: Komarek Adam M. , Spoor Max , Feng Shuyi , Shi Xiaoping
Published: January 2017

Purpose

The purpose of this paper is to explore the expansion of agricultural production into marginal lands, also known as “wasteland,” and examine the association between political capital, household income, and using additional marginal lands for agriculture in the Xinjiang Uyghur Autonomous Region of western China.

Design/methodology/approach

The paper uses exploratory data analyses methods, including descriptive statistics, graphical analysis, econometrics and propensity score matching, and data from a 2008 survey of 342 households in Awat County of Aksu Prefecture to explore the role of political capital in an agricultural household setting.

Findings

Preliminary results suggest that wasteland usage has a positive association with income, and that household political capital, in the form of Communist Party membership or being a village cadre, correlates with wasteland usage because it improves access to irrigation water.

Originality/value

A constant topic of debate in China is the role of political capital in influencing livelihoods. The authors aim to add modest insights into this debate and provide a starting point to foster additional debates regarding the role of political capital, rural livelihoods, and natural resource usage.
Profit efficiency analysis of rice production in Taiwan
Authors: Chang Tsaiyu , Takahashi Daisuke , Yang Chih-Kuan
Published: January 2017

Purpose

The purpose of this paper is to analyze and compare the profit efficiency of custom and self-farming methods of rice production in Taiwan.

Design/methodology/approach

This study examines the nature and extent of the profitability and profit efficiency of custom and self-farming based on a farm survey in Taiwan. Furthermore, it estimates the stochastic profit frontier to measure the degree of inefficiency and analyze the determinants of these inefficiencies.

Findings

The profitability and profit efficiency of custom farming are lower than for self-farming, and the differences in profitability are more significant for large rice farmers. The estimation results show that the custom farming area and the farmer’s age decrease efficiency and, regardless of the farming style used, larger farms have higher profit efficiency.

Research limitations/implications

This study’s findings show that self-farming is more favorable than custom farming for profit efficiency. This study examined this problem by conducting a regression adjustment for explanatory variables, but did not remove all self-selection bias, which may occur between profit efficiency and the choice of farming system.

Originality/value

Previous studies that measured the efficiency of rice farming often considered cost efficiency by the cost function, and ignored the increased profit from producing high-quality rice. This study used a one-step estimation of the profit frontier function to measure the degree of inefficiency and analyze the determinants of this inefficiency.