bluuebunny/crossref_metadata_2025 huggingface dataset:
Antibiotics for early‐onset neonatal infection: a summary of the NICE guideline 2012
Authors: Mugglestone Moira A , Murphy M Stephen , Visintin Cristina , Howe David T , Turner Mark A
Published: April 2014

Key content

Early‐onset neonatal infection (infection arising within 72 hours of birth) is an important cause of morbidity and mortality and is often caused by Streptococcus agalactiae (group B streptococcus [GBS]).

Identifying and assessing risk factors for early‐onset neonatal infection before and during labour and birth is integral to clinical management.

Intrapartum antibiotic prophylaxis (IAP) to prevent early‐onset neonatal infection is effective when given to women with particular risk factors, including maternal GBS colonisation.

When IAP is given specifically to prevent early‐onset neonatal infection with GBS the National Institute for Health and Care Excellence (NICE) recommends using benzylpenicillin.

Alternative antibiotic regimens are appropriate for women who are allergic to penicillin or where local microbiological surveillance data indicate antibiotic resistance.

Learning objectives

To be aware of the risk factors for early‐onset neonatal infection.

To understand how IAP can reduce the risk of an early‐onset neonatal infection.

To know which antibiotic to use for IAP of GBS.

Ethical issues

How should decisions about whether to administer IAP trade off the potential benefit to the baby of preventing an early‐onset neonatal infection and potential harms to the woman, such as, allergic reactions and increased medicalisation of pregnancy?

How should decisions about the choice of antibiotics used in intrapartum prophylaxis take account of the risk of promoting antibiotic resistance?
Providing an obstetric teaching programme in a resource poor country
Authors: Fabre‐Gray Anna , Bills Victoria
Published: April 2014

Key content

A practical template for a structured approach when planning a voluntary, obstetric teaching programme in low and middle‐income countries.

How to establish common, obtainable learning objectives that meet the needs of both participants and recipients.

Examples of teaching programmes and practical educational resources.

Discussion of cultural differences in medical practice and how to break down barriers.

Demonstrate that teaching programmes can be mutually beneficial.

Strategies for providing continuation of the educational link programme.

Learning objectives

To provide readers with a template for a structured approach when planning a voluntary, obstetric teaching programme in a resource poor country.

Methods to optimise time and resources in order to benefit the recipients of such a programme.

To understand the benefits of a cooperative approach between participants and recipients when developing and implementing a teaching strategy.

To avoid common pitfalls when planning and implementing an obstetric teaching programme in a low and middle‐income country (LMIC).

Ethical issues

Are short‐term, voluntary, teaching‐focused visits to resource poor countries sustainable?

How does the provision of teaching programmes benefit the recipients in the long‐term?
Cortical HCN channels: function, trafficking and plasticity
Authors: Shah Mala M.
Published: April 2014

The hyperpolarization‐activated cyclic nucleotide‐gated (HCN) channels belong to the superfamily of voltage‐gated potassium ion channels. They are, however, activated by hyperpolarizing potentials and are permeable to cations. Four HCN subunits have been cloned, of which HCN1 and HCN2 subunits are predominantly expressed in the cortex. These subunits are principally located in pyramidal cell dendrites, although they are also found at lower concentrations in the somata of pyramidal neurons as well as other neuron subtypes. HCN channels are actively trafficked to dendrites by binding to the chaperone protein TRIP8b. Somato‐dendritic HCN channels in pyramidal neurons modulate spike firing and synaptic potential integration by influencing the membrane resistance and resting membrane potential. Intriguingly, HCN channels are present in certain cortical axons and synaptic terminals too. Here, they regulate synaptic transmission but the underlying mechanisms appear to vary considerably amongst different synaptic terminals. In conclusion, HCN channels are expressed in multiple neuronal subcellular compartments in the cortex, where they have a diverse and complex effect on neuronal excitability.
Molecular mechanisms of neuronal nitric oxide synthase in cardiac function and pathophysiology
Authors: Zhang Yin Hua , Jin Chun Zi , Jang Ji Hyun , Wang Yue
Published: April 2014

Neuronal nitric oxide synthase (nNOS or NOS1) is the major endogenous source of myocardial nitric oxide (NO), which facilitates cardiac relaxation and modulates contraction. In the healthy heart it regulates intracellular Ca2+, signalling pathways and oxidative homeostasis and is upregulated from early phases upon pathogenic insult. nNOS plays pivotal roles in protecting the myocardium from increased oxidative stress, systolic/diastolic dysfunction, adverse structural remodelling and arrhythmias in the failing heart. Here, we show that the downstream target proteins of nNOS and underlying post‐transcriptional modifications are shifted during disease progression from Ca2+‐handling proteins [e.g. PKA‐dependent phospholamban phosphorylation (PLN‐Ser16)] in the healthy heart to cGMP/PKG‐dependent PLN‐Ser16 with acute angiotensin II (Ang II) treatment. In early hypertension, nNOS‐derived NO is involved in increases of cGMP/PKG‐dependent troponin I (TnI‐Ser23/24) and cardiac myosin binding protein C (cMBP‐C‐Ser273). However, nNOS‐derived NO is shown to increase S‐nitrosylation of various Ca2+‐handling proteins in failing myocardium. The spatial compartmentation of nNOS and its translocation for diverse binding partners in the diseased heart or various nNOS splicing variants and regulation in response to pathological stress may be responsible for varied underlying mechanisms and functions. In this review, we endeavour to outline recent advances in knowledge of the molecular mechanisms mediating the functions of nNOS in the myocardium in both normal and diseased hearts. Insights into nNOS gene regulation in various tissues are discussed. Overall, nNOS is an important cardiac protector in the diseased heart. The dynamic localization and various mediating mechanisms of nNOS ensure that it is able to regulate functions effectively in the heart under stress.
The microbiota–gut–brain axis in gastrointestinal disorders: stressed bugs, stressed brain or both?
Authors: De Palma Giada , Collins Stephen M. , Bercik Premysl , Verdu Elena F.
Published: April 2014

The gut–brain axis is the bidirectional communication between the gut and the brain, which occurs through multiple pathways that include hormonal, neural and immune mediators. The signals along this axis can originate in the gut, the brain or both, with the objective of maintaining normal gut function and appropriate behaviour. In recent years, the study of gut microbiota has become one of the most important areas in biomedical research. Attention has focused on the role of gut microbiota in determining normal gut physiology and immunity and, more recently, on its role as modulator of host behaviour (‘microbiota–gut–brain axis’). We therefore review the literature on the role of gut microbiota in gut homeostasis and link it with mechanisms that could influence behaviour. We discuss the association of dysbiosis with disease, with particular focus on functional bowel disorders and their relationship to psychological stress. This is of particular interest because exposure to stressors has long been known to increase susceptibility to and severity of gastrointestinal diseases.
Balance between the proximal dendritic compartment and the soma determines spontaneous firing rate in midbrain dopamine neurons
Authors: Jang Jinyoung , Um Ki Bum , Jang Miae , Kim Shin Hye , Cho Hana , Chung Sungkwon , Kim Hyun Jin , Park Myoung Kyu
Published: April 2014

Key points

The electrical coupling between the soma and dendritic compartments has been regarded as a key determinant for the spontaneous firing rate (SFR) in midbrain dopamine neurons.

Isolated nigral dopamine neurons showed a wide range of soma size and a variable number of primary dendrites but preserved a quite consistent SFR.

The SFR was not correlated with soma size or with the number of primary dendrites, but it was strongly correlated with the area ratios of the proximal dendritic compartments to the somatic compartment.

Tetrodotoxin puff and local Ca2+ perturbation experiments, computer simulation, and local glutamate uncaging experiments suggest the importance of the proximal dendritic compartments in pacemaker activity.

These results lead us to a novel conclusion that the proximal dendritic compartments, not the whole dendritic compartments, play a key role in the somatodendritic balance that determines the SFR in dopamine neurons.

Midbrain dopamine (DA) neurons are slow intrinsic pacemakers that require the elaborate composition of many ion channels in the somatodendritic compartments. Understanding the major determinants of the spontaneous firing rate (SFR) of midbrain DA neurons is important because they determine the basal DA levels in target areas, including the striatum. As spontaneous firing occurs synchronously at the soma and dendrites, the electrical coupling between the soma and dendritic compartments has been regarded as a key determinant for the SFR. However, it is not known whether this somatodendritic coupling is served by the whole dendritic compartments or only parts of them. In the rat substantia nigra pars compacta (SNc) DA neurons, we demonstrate that the balance between the proximal dendritic compartment and the soma determines the SFR. Isolated SNc DA neurons showed a wide range of soma size and a variable number of primary dendrites but preserved a quite consistent SFR. The SFR was not correlated with soma size or with the number of primary dendrites, but it was strongly correlated with the area ratios of the proximal dendritic compartments to the somatic compartment. Tetrodotoxin puff and local Ca2+ perturbation experiments, computer simulation, and local glutamate uncaging experiments suggest the importance of the proximal dendritic compartments in pacemaker activity. These data indicate that the proximal dendritic compartments, not the whole dendritic compartments, play a key role in the somatodendritic balance that determines the SFR in DA neurons.
Lattice relaxation and misfit dislocations in nonlinearly graded InxGa1 − xAs/GaAs (001) and GaAs1 − yPy/GaAs (001) metamorphic buffer layers
Authors: Kujofsa Tedi , Ayers John E.
Published: April 2014

Recent results have shown that nonlinearly graded buffer layers may be beneficial for the reduction of threading dislocation densities in metamorphic semiconductor devices. In this work, the authors have studied the equilibrium strain relaxation and misfit dislocation densities in nonlinearly graded heterostructures with logarithmic grading, and compare the cases of InxGa1−xAs/GaAs and GaAs1−yPy/GaAs buffer layers. The authors show that differences in the elastic stiffness constants give rise to significantly different behavior in these two commonly used buffer layer systems. Moreover, the width of the dislocated region, the average misfit dislocation density, and surface in-plane strain may be related to the nonlinearity coefficient of the grading profile.
Examining Social Capital Development Among Volunteers of a Multinational Sport-for-Development Event
Authors: Peachey Jon Welty , Bruening Jennifer , Lyras Alexis , Cohen Adam , Cunningham George B.
Published: April 2014

Much sport-for-development (SFD) research has focused on the impact initiatives have on participants, and not on other stakeholders such as volunteers. Some research suggests volunteerism enables social capital gains, while other scholars have been skeptical, with even less known about how volunteers are impacted by working for SFD events rather than for ongoing programs. Therefore, the purpose of this study was to investigate how, if at all, a large, multinational SFD event contributed to social capital development of volunteers. Findings revealed volunteers experienced social capital development through building relationships, learning, and enhanced motivation to work for social change and reciprocity. As very little research has examined the efficacy of SFD events in contributing to social capital development, the findings extend the literature on SFD events. It would be prudent for SFD events to target programming to impact the experience of volunteers to retain them and contribute to social capital development.
MexY-Promoted Aminoglycoside Resistance in Pseudomonas aeruginosa: Involvement of a Putative Proximal Binding Pocket in Aminoglycoside Recognition
Authors: Lau Calvin Ho-Fung , Hughes Daniel , Poole Keith
Published: April 2014

The resistance-nodulation-division (RND) family multidrug efflux system MexXY-OprM is a major determinant of aminoglycoside resistance in
Pseudomonas aeruginosa
, although the details of aminoglycoside recognition and export by MexY, the substrate-binding RND component of this efflux system, have not been elucidated. To identify regions/residues of MexY important for aminoglycoside resistance, plasmid-borne
mexY
was mutagenized and mutations that impaired MexY-promoted aminoglycoside (streptomycin) resistance were identified in a Δ
mexY
strain of
P. aeruginosa
. Sixty-one streptomycin-sensitive
mexY
mutants were recovered; among these, 7 unique mutations that yielded wild-type levels of MexY expression were identified. These mutations compromised resistance to additional aminoglycosides and to other antimicrobials and occurred in both the transmembrane and periplasmic regions of the protein. Mapping of the mutated residues onto a 3-dimensional structure of MexY modeled on
Escherichia coli
AcrB revealed that these tended to occur in regions implicated in general pump operation (transmembrane domain) and MexY trimer assembly (docking domain) and, thus, did not provide insights into aminoglycoside recognition. A region corresponding to a proximal binding pocket connected to a periplasm-linked cleft, part of a drug export pathway of AcrB, was identified in MexY and proposed to play a role in aminoglycoside recognition. To test this, selected residues (K79, D133, and Y613) within this pocket were mutagenized and the impact on aminoglycoside resistance was assessed. Mutations of D133 and Y613 compromised aminoglycoside resistance, while, surprisingly, the K79 mutation enhanced aminoglycoside resistance, confirming a role for this putative proximal binding pocket in aminoglycoside recognition and export.

IMPORTANCE
Bacterial RND pumps do not typically accommodate highly hydrophilic agents such as aminoglycosides, and it is unclear how those, such as MexY, which accommodate these unique substrates, do so. The results presented here indicate that aminoglycosides are likely not captured and exported by this RND pump component in a unique manner but rather utilize a previously defined export pathway that involves a proximal drug-binding pocket that is also implicated in the export of nonaminoglycosides. The observation, too, that a mutation in this pocket enhances MexY-mediated aminoglycoside resistance (K79A), an indication that it is not optimally designed to accommodate these agents, lends further support to earlier proposals that antimicrobials are not the intended pump substrates.
Global Population Structure and Evolution of Bordetella pertussis and Their Relationship with Vaccination
Authors: Bart Marieke J. , Harris Simon R. , Advani Abdolreza , Arakawa Yoshichika , Bottero Daniela , Bouchez Valérie , Cassiday Pamela K. , Chiang Chuen-Sheue , Dalby Tine , Fry Norman K. , Gaillard María Emilia , van Gent Marjolein , Guiso Nicole , Hallander Hans O. , Harvill Eric T. , He Qiushui , van der Heide Han G. J. , Heuvelman Kees , Hozbor Daniela F. , Kamachi Kazunari , Karataev Gennady I. , Lan Ruiting , Lutyńska Anna , Maharjan Ram P. , Mertsola Jussi , Miyamura Tatsuo , Octavia Sophie , Preston Andrew , Quail Michael A. , Sintchenko Vitali , Stefanelli Paola , Tondella M. Lucia , Tsang Raymond S. W. , Xu Yinghua , Yao Shu-Man , Zhang Shumin , Parkhill Julian , Mooi Frits R.
Published: April 2014

Bordetella pertussiscauses pertussis, a respiratory disease that is most severe for infants. Vaccination was introduced in the 1950s, and in recent years, a resurgence of disease was observed worldwide, with significant mortality in infants. Possible causes for this include the switch from whole-cell vaccines (WCVs) to less effective acellular vaccines (ACVs), waning immunity, and pathogen adaptation. Pathogen adaptation is suggested by antigenic divergence between vaccine strains and circulating strains and by the emergence of strains with increased pertussis toxin production. We applied comparative genomics to a worldwide collection of 343B. pertussisstrains isolated between 1920 and 2010. The global phylogeny showed two deep branches; the largest of these contained 98% of all strains, and its expansion correlated temporally with the first descriptions of pertussis outbreaks in Europe in the 16th century. We found little evidence of recent geographical clustering of the strains within this lineage, suggesting rapid strain flow between countries. We observed that changes in genes encoding proteins implicated in protective immunity that are included in ACVs occurred after the introduction of WCVs but before the switch to ACVs. Furthermore, our analyses consistently suggested that virulence-associated genes and genes coding for surface-exposed proteins were involved in adaptation. However, many of the putative adaptive loci identified have a physiological role, and further studies of these loci may reveal less obvious ways in whichB. pertussisand the host interact. This work provides insight into ways in which pathogens may adapt to vaccination and suggests ways to improve pertussis vaccines.

IMPORTANCEWhooping cough is mainly caused byBordetella pertussis, and current vaccines are targeted against this organism. Recently, there have been increasing outbreaks of whooping cough, even where vaccine coverage is high. Analysis of the genomes of 343B. pertussisisolates from around the world over the last 100 years suggests that the organism has emerged within the last 500 years, consistent with historical records. We show that global transmission of new strains is very rapid and that the worldwide population ofB. pertussisis evolving in response to vaccine introduction, potentially enabling vaccine escape.
Considering iatrogenic psychosis after malignant glioma resection
Authors: Shah Ashish Harish , Gordon Catherine E , Bregy Amade , Shah Nirav , Komotar Ricardo Jorge
Published: April 2014

It is generally well known that medial temporal lobe resections have been associated with a variety of postoperative neuropsychiatric disturbances. Most of the neurosurgical literature on psychiatric disturbances after a temporal lobectomy concern patients with a strong history of epilepsy; however, relatively few articles have been reported due to a mesial temporal lobectomy following tumour removal. We report the case of a patient who underwent a gross total resection of a malignant astrocytoma in the temporal lobe who developed transient psychosis. Difficulties in diagnosing and predicting this condition are discussed as along with management considerations.
Traumatic appendicitis misdiagnosed as a case of haemoperitoneum
Authors: Ahmed Syed Tausif , Ranjan Rajeev , Saha Subhendu Bikas , Singh Balbodh
Published: April 2014

Acute appendicitis is one of the most common emergencies handled by a surgeon. Various aetiologies of acute appendicitis have been proposed but none have been proved. Trauma too has been proposed as a cause of acute appendicitis. Here we present a case of blunt trauma abdomen which was explored to rule out a perforation of hollow viscous organ and haemoperitoneum, but at the time of exploration a perforated appendicitis was found. The chronological order of events points towards blunt trauma as the probable cause of this appendicitis. This case also highlights the fact that even if trauma was not the cause of acute appendicitis, acute appendicitis should still be kept in the differential diagnosis of a patient presenting with pain in the right lower abdomen and a history of trauma.
Twelve-year-old boy with recurrent presentations of shortness of breath: an intraluminal tracheal tumour
Authors: Rai Birendra , Mohd Din Fazly Helmi , O'Byrne James Joseph , Sharif Farhana
Published: April 2014

A 12-year-old boy was admitted with symptoms of recurrent shortness of breath since 12 months along with mild intermittent retrosternal chest pain that had developed 3 weeks ago prior to admission. He was previously treated for asthma with no improvement. Initial posteroanterior chest X-ray (CXR) revealed no abnormality on two occasions. Lateral CXR showed a mass lesion in the distal trachea which was subsequently confirmed by a CT scan of the chest.
Littre’s hernia with an impalpable testis in a boy: a diagnostic dilemma
Authors: Singh Rashmi Roshan , Sinha Chandrasen Kumar , Joshi Ashwini
Published: April 2014

Littre's hernia is a rare clinical entity. The presence of a Littre's hernia in a 2-year-old boy with an impalpable testis is even rarer. We describe this interesting case with a review of the literature.
Retropharyngeal abscess complicating ‘innocent’ foreign body ingestion
Authors: Vourexakis Zacharias , Konu Prosper
Published: April 2014

An adult patient presented to the emergency department with pharyngeal discomfort on swallowing, persisting several hours after lunch. Transnasal fibre-optic endoscopy performed by an otolaryngologist identified a hypopharyngeal foreign body, and the stalk of a dry leaf partially penetrating the mucosa was easily removed under general anaesthesia. Symptoms regressed completely and the patient was discharged. Two days later he presented again, reporting slight dysphagia without odynophagia or other associated symptoms. Meticulous physical examination by the same otolaryngologist revealed this time a slight asymmetry of the posterior pharyngeal wall. A history of recent pharyngeal trauma and findings on clinical examination raised clinical suspicion of retropharyngeal abscess which was supported by CT scan findings. The diagnosis was confirmed in the operating theatre where a purulent collection was drained under new general anaesthesia.
Rare presentation of sebaceous hyperplasia
Authors: Lester Rachael A , Torgerson Rochelle R , Sandhu Nicole P
Published: April 2014

A 23-year-old woman presented with an 8-month history of asymptomatic thickening of the central areola bilaterally and oily nipple discharge. On examination, there were yellowish-pink papules coalescing into plaques bilaterally. Biopsy showed ectopic sebaceous glands (Montgomery tubercles), known asbilateral areolar sebaceous hyperplasia.
Correlations of skin fold thickness and validation of prediction equations using DEXA as the gold standard for estimation of body fat composition in Pakistani children
Authors: Hussain Zainab , Jafar Tazeen , Zaman Maseeh uz , Parveen Riffat , Saeed Farzan
Published: April 2014

Objective

To determine the correlation between dual energy X-ray absorptiometry (DEXA) and skin fold thickness (SKF) equations for estimation of body fat (BF) composition in secondary school children and validation of prediction equations by Slaughter, Goran and Dezenberg.

Design

Cross sectional analytical study.

Setting

Joint Commission for International Accredited (JCIA) tertiary care hospital of Karachi, Pakistan from January 2010 to May 2010.

Participants

The study was approved by the Hospital's ethical review committee. Written and verbal consents were obtained from principals of two schools and parents of 99 children (mean age of 14±1.89 years; min–max 9–19 years; 54 men and 45 women) accrued in study. DEXA scan was acquired and SKF was measured at angle of the scapula, iliac crest and mid-arm for bicep and tricep skin folds using Holtain Callipers. Correlations were established between estimated fat mass (FM) and per cent BF (%BF) calculated by DEXA and those predicted by prediction equations. On obtaining significant correlation of >0.5, overall accuracy,precisionand bias was calculated.

Results

There was an overall increased adiposity in females with FM of 3.57 kg and %BF 6.2% higher than male counterparts (p<0.05). Slaughter equation predicted %BF accurately with overall high accuracy, minimal bias and with goodprecisionwith DEXA. Dezenberg and Goran equations had significant bias in prediction of FM which was statistically significant with low level of accuracy of the Goran equation.

Conclusions

We conclude that Slaughter equation for estimating %BF showed reasonable validation with DEXA. Nevertheless further studies with consideration for maturity and ethnicity are warranted for better results. However, for estimation of FM, previously formulated equations by Goran and Dezenberg showed significant difference in our population. We do recommend further studies for developing and validation of skin fold equations specific to Pakistani paediatric population.
Is density of neighbourhood restaurants associated with BMI in rural Chinese adults? A longitudinal study from the China Health and Nutrition Survey
Authors: Du Wenwen , Su Chang , Wang Huijun , Wang Zhihong , Wang Youfa , Zhang Bing
Published: April 2014

Objectives

The neighbourhood availability of restaurants has been linked to the weight status. However, little is known regarding the relation between access to restaurant and obesity among the Chinese population. This study aims to explore the relationship between neighbourhood restaurant density and body mass index (BMI) in rural China.

Design

A longitudinal study using data from the China Health and Nutrition Survey (CHNS) was conducted. Participants aged 18 and older from the 2004, 2006, 2009 and 2011 CHNS were recruited Separate sex-stratified random intercept-slope growth models of repeated BMI observations were estimated in the study.

Setting

The data were derived from rural communities in nine provinces in China.

Participants

There were 11 835 male and 12 561 female person-years assessed in this study.

Outcomes

The primary outcome of this study was weight status. It is defined as a BMI value, a continuous variable which is calculated by dividing weight (kg) by the square of height (m2).

Results

The study indicated that among men an increase of one indoor restaurant in the neighbourhood was associated with a 0.01 kg/m2increase in BMI, and an increase of one fixed outdoor food stall was associated with a 0.01 kg/m2decrease in BMI, whereas among women, an increase of one indoor restaurant in the neighbourhood was associated with a 0.005 kg/m2increase in BMI, and an increase of one fast-food restaurant and one fixed outdoor food stall was associated with a 0.02 and 0.004 kg/m2decline in BMI, respectively.

Conclusions

The density of neighbourhood restaurants was found to be significantly related to BMI in rural China. The results indicated that providing healthy food choices and developing related public health policies are necessary to tackle obesity among rural Chinese adults.
A LOW POWER 13-BIT 50MS/s RECIRCULATING PIPELINE ANALOG TO DIGITAL CONVERTER
Authors: ESMAILI ARASH , BABAZADEH HADISEH , HADIDI KHAYROLLAH , KHOEI ABDOLLAH
Published: April 2014

A 13-bit analog-to-digital converter (ADC) is designed in 0.35 μm CMOS technology that reduces the power consumption through sharing the resources between pipeline stages. Using a dummy sample-and-hold (S/H) and recirculating concept the requirements for the first stage are relaxed and the design restrictions are resolved. This ADC does not use a dedicated S/H and reaches a speed of 50 MS/s. The design is tested with TSMC mixed-signal 0.35 μm technology and post layout simulations shows over 75 dB Signal-to-Noise and Distortion-Ratio (SNDR) and over 85 dB Spurious Free Dynamic Range (SFDR) at the Nyquist frequency. The designed chip occupies an area of 1.3 mm–0.7 mm and consumes 164 mW power at Nyquist from a 3.3 V supply.
Control of Bifurcation and Chaos in a Class of Digital Tanlock Loops with Modified Loop Structure
Authors: Sarkar Bishnu Charan , De Sarkar Saumendra Sankar , Banerjee Tanmoy
Published: April 2014

A detailed parametric space study of the nonlinear behavior of a kind of Digital Tanlock Loops (DTL) incorporating a modified loop structure using a time delayed feedback technique has been studied in this paper. The analytical study reveals that the modified loop shows better performance compared to a conventional DTL (CDTL). The superiority of the modified DTL (MDTL) has been established by a numerical simulation study. Two parameter bifurcation diagrams, supported by Lyapunov exponent spectrums, have been used to give a detailed idea about the nonlinear dynamics of the loop for a wide parameter range. The MDTL shows large frequency acquisition range (FAR) and faster convergence time (CT) than a CDTL for suitably chosen values of the design parameter. An estimate for the optimum value of the structure parameter for quick convergence has also been presented in the present study.
Correlation Dimension of Fractional Gaussian Noise: New Evidence from Wavelets
Authors: Dhifaoui Zouhaier , Kortas Hedi , Benammou Samir
Published: April 2014

In this paper, we study the behavior of the correlation dimension estimated using the Grassberger–Procaccia (GP) algorithm [Grassberger & Procaccia, 1983] in the wavelet domain for functions belonging to Hölder space. We prove that, as the wavelet scale level tends to infinity, the GP correlation dimension estimate tends to zero. Applying this result to the trajectories of the fractional Brownian motion process and using basic properties of the wavelet transform, we show that, for the fractional Gaussian noise process (fGn), the correlation dimension estimated by the GP procedure converges to the zero value. As the fractional Gaussian noise is a stochastic process with 1/fα spectrum, -1 < α < 1, our results confirm Osborne and Provenzale's assertion that colored random noise leads to the convergence of the GP-based correlation dimension estimator. However, our result holds for a different range of the spectrum exponent values. Moreover, for the fGn class of random processes, we found no correspondence between the value of the scaling exponent H and the value of the correlation dimension estimated by the GP algorithm as the latter is simply zero.
Effects of Delay and Diffusion on the Dynamics of a Leslie–Gower Type Predator–Prey Model
Authors: Zhang Jia-Fang , Yan Xiang-Ping
Published: April 2014

In this paper, we consider the effects of time delay and space diffusion on the dynamics of a Leslie–Gower type predator–prey system. It is shown that under homogeneous Neumann boundary condition the occurrence of space diffusion does not affect the stability of the positive constant equilibrium of the system. However, we find that the incorporation of a discrete delay representing the gestation of prey species can not only destabilize the positive constant equilibrium of the system but can also cause a Hopf bifurcation at the positive constant equilibrium as it crosses some critical values. In particular, we prove that these Hopf bifurcations' periodic solutions are all spatially homogeneous if the diffusive rates are suitably large, which has the same properties as periodic solutions of the corresponding delayed system without diffusion. However, if the diffusive rates are suitably small, then the system will generate spatially nonhomogeneous periodic solutions. The results in this work demonstrate that diffusion plays an important role in deriving complex spatiotemporal dynamics.
The Geometry of Quadratic Polynomial Differential Systems with a Finite and an Infinite Saddle-Node (A, B)
Authors: Artés Joan C. , Rezende Alex C. , Oliveira Regilene D. S.
Published: April 2014

Planar quadratic differential systems occur in many areas of applied mathematics. Although more than one thousand papers have been written on these systems, a complete understanding of this family is still missing. Classical problems, and in particular, Hilbert's 16th problem [Hilbert, 1900, 1902], are still open for this family. In this paper, we study the bifurcation diagram of the family QsnSN which is the set of all quadratic systems which have at least one finite semi-elemental saddle-node and one infinite semi-elemental saddle-node formed by the collision of two infinite singular points. We study this family with respect to a specific normal form which puts the finite saddle-node at the origin and fixes its eigenvectors on the axes. Our aim is to make a global study of the family [Formula: see text] which is the closure of the set of representatives of QsnSN in the parameter space of that specific normal form. This family can be divided into three different subfamilies according to the position of the infinite saddle-node, namely: (A) with the infinite saddle-node in the horizontal axis, (B) with the infinite saddle-node in the vertical axis and (C) with the infinite saddle-node in the bisector of the first and third quadrants. These three subfamilies modulo the action of the affine group and times homotheties are four-dimensional. Here, we provide the complete study of the geometry with respect to a normal form of the first two families, (A) and (B). The bifurcation diagram for the subfamily (A) yields 38 phase portraits for systems in [Formula: see text] (29 in QsnSN(A)) out of which only three have limit cycles and 13 possess graphics. The bifurcation diagram for the subfamily (B) yields 25 phase portraits for systems in [Formula: see text] (16 in QsnSN(B)) out of which 11 possess graphics. None of the 25 portraits has limit cycles. Case (C) will yield many more phase portraits and will be written separately in a forthcoming new paper. Algebraic invariants are used to construct the bifurcation set. The phase portraits are represented on the Poincaré disk. The bifurcation set of [Formula: see text] is the union of algebraic surfaces and one surface whose presence was detected numerically. All points in this surface correspond to connections of separatrices. The bifurcation set of [Formula: see text] is formed only by algebraic surfaces.
Implementations of Modified Chaotic Neural Models with Analog Reconfigurable Hardware
Authors: Korkmaz Nimet , Kilic Recai
Published: April 2014

This paper focuses on implementations of two modified Aihara's chaotic neuron models and a simple chaotic neural network constructed with two chaotic neurons in a programmable and reconfigurable manner with an analog programmable device, FPAA (Field Programmable Analog Array). After testing the chaotic behaviors of two chaotic neuron models and a simple chaotic neural network through numerical analyses that consist of time domain responses, phase portrait illustrations and bifurcation diagrams, the experimental setup is constructed with a FPAA device. The parametric adjustments of chaotic neural structures are possible with the proposed flexible design methodology and different chaotic neuron models are constructed on the same reconfigurable device without any hardware changes. Experimental results verify the dynamic behaviors of these chaotic neural structures and demonstrate the efficiency of programmable implementations.
Design and Circuit Implementation of Discrete-Time Chaotic Systems with Modulus of Triangular Wave Functions
Authors: Shen Chaowen , Yu Simin , Lü Jinhu
Published: April 2014

This paper investigates n-dimensional discrete-time systems with modulus of triangular wave functions. First, a proof is given to the existence of chaos in the sense of Li–Yorke. Then, taking the three-dimensional case as a typical example, a circuit is designed under the condition of a limited region, with experimental results demonstrated.
Design and ARM Platform-Based Realization of Digital Color Image Encryption and Decryption via Single State Variable Feedback Control
Authors: Zheng Hanzhong , Yu Simin , Lü Jinhu
Published: April 2014

In this paper, discrete-time chaotic systems under single state variable feedback control are studied, and drive-response synchronization is investigated. To that end, ARM platform-based digital color image encryption and decryption using a chaotic stream cipher is designed and implemented, with experimental results demonstrated.
Stochastic and Coherence Resonance in a Dressed Neuron Model
Authors: Liu Ying , Xu Xinmin
Published: April 2014

The noise induced stochastic behaviors, in terms of stochastic resonance (SR) and coherence resonance (CR), have been widely reported in many nonlinear systems in different disciplines. In particular, in neuroscience, both the phenomena of SR and CR have been discovered. However, the traditional studies only focus on the dynamical behaviors of the neurons without considering the effects of other biological cells. It is known that neurons are surrounded by a number of glial cells. Being a subgroup of glial cells, astrocytes have been argued to take part in neuronal signal processing. Therefore, it is more reasonable to study the dynamics of a neuron by incorporating the effect of astrocyte, which is termed as dressed neuron. In this paper, the stochastic behaviors of a dressed Hodgkin–Huxley neuron with mutual neuron-astrocyte interaction are studied, and the effects of astrocyte on different resonance mechanisms are analyzed. Simulation results show that the astrocyte plays a similar role as noise in the stochastic behaviors of a neuron, which enhances the performance of a neuron in signal transduction via resonance mechanisms.
Complex Dynamics in the Unified Lorenz-Type System
Authors: Yang Qigui , Chen Yuming
Published: April 2014

This paper is devoted to the analysis of complex dynamics of the unified Lorenz-type system (ULTS) with six parameters, which contain common chaotic systems as its particular cases. First, some important local dynamics such as pitchfork bifurcation, Hopf bifurcation, and the stability of nondegenerate and double-zero equilibria are systematically investigated using the parameter-dependent center manifold theory combined with some bifurcation theories. Some adequate conditions for guaranteeing the occurrence of degenerate Hopf bifurcation (DHB) and the stability of the equilibria are given. Second, it is found that if DHB does not generate at the trivial equilibrium but generates at two symmetric nontrivial equilibria, then a small perturbation can lead that ULTS to exhibit a chaotic attractor. Interestingly, such a case can take place in the Chen and Lü systems (two common chaotic systems) but cannot take place in the Lorenz and Yang systems (the other two common chaotic systems), essentially distinguishing the Lorenz system from the Chen system. In addition, it is numerically verified that both of the latter two systems can exhibit the coexistence of both a chaotic attractor and multiple limit cycles but the former two systems seem not to have this property. If DHB takes place simultaneously at three equilibria of ULTS, then this system has an invariant algebraic surface, and rigorously prove the existence of some global dynamics such as periodic orbit, center, homoclinic/heteroclinic orbits. Third, it is shown that a singularly degenerate heteroclinic cycle can exist in the case of b = 0 (where b is a parameter of ULTS, like that in the Lorenz system), and a chaotic attractor can be generated by perturbing this cycle for small b > 0. These results altogether indicate that the ULTS can exhibit complex dynamics, and provide a more reasonable classification for chaos in the 3D autonomous chaotic ODE systems that were developed based on the Lorenz system, in contrast to the previous studies.
Nontrivial, nonnegative periodic solutions of a system of singular-degenerate parabolic equations with nonlocal terms
Authors: Fragnelli Genni , Mugnai Dimitri , Nistri Paolo , Papini Duccio
Published: April 2014

We study the existence of nontrivial, nonnegative periodic solutions for systems of singular-degenerate parabolic equations with nonlocal terms and satisfying Dirichlet boundary conditions. The method employed in this paper is based on the Leray–Schauder topological degree theory. However, verifying the conditions under which such a theory applies is more involved due to the presence of the singularity. The system can be regarded as a possible model of the interactions of two biological species sharing the same isolated territory, and our results give conditions that ensure the coexistence of the two species.
On the strong homotopy associative algebra of a foliation
Authors: Vitagliano Luca
Published: April 2014

An involutive distribution C on a smooth manifold M is a Lie-algebroid acting on sections of the normal bundle TM/C. It is known that the Chevalley–Eilenberg complex associated to this representation of C possesses the structure 𝕏 of a strong homotopy Lie–Rinehart algebra. It is natural to interpret 𝕏 as the (derived) Lie–Rinehart algebra of vector fields on the space P of integral manifolds of C. In this paper, we show that 𝕏 is embedded in an A∞-algebra 𝔻 of (normal) differential operators. It is natural to interpret 𝔻 as the (derived) associative algebra of differential operators on P. Finally, we speculate about the interpretation of 𝔻 as the universal enveloping strong homotopy algebra of 𝕏.
A Survey of Small-Scale Unmanned Aerial Vehicles: Recent Advances and Future Development Trends
Authors: Cai Guowei , Dias Jorge , Seneviratne Lakmal
Published: April 2014

This paper provides a brief overview on the recent advances of small-scale unmanned aerial vehicles (UAVs) from the perspective of platforms, key elements, and scientific research. The survey starts with an introduction of the recent advances of small-scale UAV platforms, based on the information summarized from 132 models available worldwide. Next, the evolvement of the key elements, including onboard processing units, navigation sensors, mission-oriented sensors, communication modules, and ground control station, is presented and analyzed. Third, achievements of small-scale UAV research, particularly on platform design and construction, dynamics modeling, and flight control, are introduced. Finally, the future of small-scale UAVs' research, civil applications, and military applications are forecasted.
Ideas for the future of the IS field
Authors: Davis Gordon B. , Gray Paul , Madnick Stuart , Nunamaker Jay F. , Sprague Ralph , Whinston Andrew
Published: April 2014

Information systems as a field of intellectual inquiry is now approximately 50 years old. It has many achievements and extensive research to its credit and has established a large group of researchers and experts worldwide. The field has changed and changed and changed again over the last half century. The question addressed in this inaugural issue article is: Where does IS go from here? This article presents the views of six of the “fathers of the field” about its directions in the years ahead. Each coauthor presents two ideas about the future. The topics covered includes continuing support of the work of organizations, emerging technologies, new ways of communicating, expanding the ways IS performs research, expanding its vision both of what IS is and of its impact, its role as a resource, its model of the IS professional and its graduates, and its staying on top of new technologies and new areas of inquiry.
Drivers of information security search behavior: An investigation of network attacks and vulnerability disclosures
Authors: Wang Jingguo , Xiao Nan , Rao H. Raghav
Published: April 2014

More and more people use search engines to seek for various information. This study investigates the search behavior that drives the search for information security knowledge via a search engine. Based on theories in information search and information security behavior we examine the effects of network attacks and vulnerability disclosures on search for information security knowledge by ordinary users. We construct a unique dataset from publicly available sources, and use a dynamic regression model to test the hypotheses empirically. We find that network attacks of current day and one day prior significantly impact the search, while vulnerability disclosure does not significantly affect the search. Implications of the study are discussed.
Modeling dynamics in agile software development
Authors: Cao Lan , Ramesh Balasubramaniam , Abdel-Hamid Tarek
Published: April 2014

Changes in the business environment such as turbulent market forces, rapidly evolving system requirements, and advances in technology demand agility in the development of software systems. Though agile approaches have received wide attention, empirical research that evaluates their effectiveness and appropriateness is scarce. Further, research to-date has investigated individual practices in isolation rather than as an integrated system. Addressing these concerns, we develop a system dynamics simulation model that considers the complex interdependencies among the variety of practices used in agile development. The model is developed on the basis of an extensive review of the literature as well as quantitative and qualitative data collected from real projects in nine organizations. We present the structure of the model focusing on essential agile practices. The validity of the model is established based on extensive structural and behavioral validation tests. Insights gained from experimentation with the model answer important questions faced by development teams in implementing two unique practices used in agile development. The results suggest that due to refactoring, the cost of implementing changes to a system varies cyclically and increases during later phases of development. Delays in refactoring also increase costs and decrease development productivity. Also, the simulation shows that pair programming helps complete more tasks and at a lower cost. The systems dynamics model developed in this research can be used as a tool by IS organizations to understand and analyze the impacts of various agile development practices and project management strategies.
A privacy protection technique for publishing data mining models and research data
Authors: Fu Yu , Chen Zhiyuan , Koru Gunes , Gangopadhyay Aryya
Published: April 2014

Data mining techniques have been widely used in many research disciplines such as medicine, life sciences, and social sciences to extract useful knowledge (such as mining models) from research data. Research data often needs to be published along with the data mining model for verification or reanalysis. However, the privacy of the published data needs to be protected because otherwise the published data is subject to misuse such as linking attacks. Therefore, employing various privacy protection methods becomes necessary. However, these methods only consider privacy protection and do not guarantee that the same mining models can be built from sanitized data. Thus the published models cannot be verified using the sanitized data. This article proposes a technique that not only protects privacy, but also guarantees that the same model, in the form of decision trees or regression trees, can be built from the sanitized data. We have also experimentally shown that other mining techniques can be used to reanalyze the sanitized data. This technique can be used to promote sharing of research data.