bluuebunny/crossref_metadata_2025 huggingface dataset:
Timing of fault reactivation in the upper crust of the St. Lawrence rift system, Canada, by K–Ar dating of illite-rich fault rocks1GEOTOP Contribution 2012-0002.
Authors: Sasseville Christian , Clauer Norbert , Tremblay Alain
Published: April 2012

Formed during late Proterozoic – early Paleozoic, the St. Lawrence rift system of eastern North America hosts an active seismic zone, also displaying evidence of subsequent tectonic reactivation in Paleozoic and Mesozoic times. However, lack of a detailed reconstruction of the basement geometry and limited geochronological constraints limit our understanding of its structural evolution. Late Silurian – Early Devonian fault reactivation is demonstrated here in typical fault sites of the St. Lawrence rift system by combining structural observations of basement structures and a mineralogical, morphological, and K–Ar isotopic study of clay-rich fault material (<0.4 µm et 1–2 µm). The K–Ar data of clay-rich size fractions from gouges of varied rock types from Saint-Laurent and Montmorency faults define two isochron ages at 436 ± 45 and 406 ± 22 Ma that are within analytical uncertainty and give an average at 421 ± 15 Ma. However, these two faulting episodes could also picture a single long-lasting phase of foreland subsidence of the Appalachian orogen starting during the Late Ordovician – Early Silurian deformation in the external Humber zone and continuing during Late Silurian – Early Devonian subsidence related to a normal faulting. This interpretation is based on a different mineral composition of the younger size fractions that consist of smectite-enriched clay minerals and could, therefore, correspond to the end of a reactivation event that was episodically active between 436 ± 45 and 406 ± 22 Ma. The faults were selectively reactivated depending on their location relative to pre-existing metamorphic and tectonic fabrics of the Grenvillian basement. The identified Late Silurian – Early Devonian reactivation of the Saint-Laurent and Montmorency faults was contemporaneous with the subsidence of the adjacent Appalachian foreland, resulting in SE-dipping faults in the crystalline basement of the St. Lawrence rift system and NW-dipping faults in the Appalachian cover.
MICROFIBER STRUCTURES FOR SENSOR APPLICATIONS
Authors: HARUN S. W. , LIM K. S. , AHMAD H.
Published: April 2012

Microfiber loop resonator (MLR) and microfiber knot resonator (MKR) are fabricated using melt-stretching method for applications in temperature and current sensor, respectively. The MLR is embedded into low refractive index polymer for robustness. Although the spacing of the transmission comb spectrum of the MLR is unchanged with temperature, the extinction ratio of the spectrum is observed to decrease linearly with temperature due to induced changes in the material's refractive index. The slope of the extinction ratio reduction against temperature is about 0.043dB/°C. With the assistance of a copper wire that is wrapped by the MKR, resonant wavelength can be tuned by varying the electric current delivered to the wire. The resonant wavelength change is based on the thermally induced optical phase shift in the MKR due to the heat produced by the flow of electric current over a short transit length. It is shown that the wavelength shift is linearly proportional to the square of current in the copper wire with a tuning slope of 46 pm/A2.
RIGOROUS NUMERICAL ANALYSIS AND CHARACTERIZATION OF A SILICON VERTICAL-SLOT NANO-WAVEGUIDE
Authors: LEUNG D. M. H. , KEJALAKSHMY N. , RAHMAN B. M. A. , GRATTAN K. T. V.
Published: April 2012

In this paper, the optical properties of a nanoscale silicon slot-waveguide has been rigorously studied by using a full vectorial H-field finite element method (VFEM) based approach. The variations of effective indices, effective areas, power densities in the slot-region and the confinement factors of the slot waveguide are thoroughly investigated. The full vectorial magnetic and electric field profiles and Poynting vector (Sz) are also presented.
STRUCTURE DEPENDENT VARIATIONS OF GROUP VELOCITY, ENERGY LOSS AND CONFINEMENT IN A REGULAR GRATED WAVEGUIDE
Authors: ALATAS HUSIN , ISKANDAR ALEXANDER A. , TJIA MAY-ON
Published: April 2012

The Green's function method in the Dyson's formulation has been employed for the ab initio numerical study of structural effects on the device performances in terms of the minimum group velocity, energy loss and energy confinement in a quasi two-dimensional grated waveguide device model. The structure parameters to be varied in this work consist of the number of the grating teeth (N) and the grating groove depth (g). It is found that those parameters exhibit roughly linear and mostly monotonous variations at the lower resonance. The reduction of the group velocity and enhancement of energy confinement are also shown to be effectively attained by increasing N, while leaving the loss parameter relatively unaffected. On the other hand, the calculated results for the upper resonance wavelength are shown to exhibit consistently non-monotonous responses to increasing g. Similarly distinct behaviors are also found in the relationship between the minimum group velocity (vg, min) and the energy loss (L) as well as that between vg, min and the confined energy (W) for various N and g at the upper resonances. This peculiarly different behaviors are shown to be related to the variations of the associated local density of states with respect to N and g calculated for the upper resonance.
ELECTROMAGNETICALLY INDUCED QUANTUM LATTICE SOLITON
Authors: GAO JIE , LI HAI , WU JIANXIONG , LI LINGYAN , MAI ZHIJIE , CHEN GUIHUA
Published: April 2012

An optical atomic discrete system through optical induction is proposed. A theoretical scheme to produce quantum discrete or lattice solitons (QLSs) in the system is presented with the use of the effects of enhanced self-phase modulation and cross-phase modulation through the giant kerr effect in the electromagnetically induced transparency. The power density and the photon flux can be tuned to a very low level by the coupling field and the soliton can propagate with very slow group velocity.
ARTERIAL WALL MECHANICS AND CLINICAL IMPLICATIONS AFTER CORONARY STENTING: COMPARISONS OF THREE STENT DESIGNS
Authors: GU LINXIA , ZHAO SHIJIA , FROEMMING STACEY R.
Published: April 2012

The goal of this work is to quantitatively assess the relationship between the reported restenosis rates and stent induced arterial stress or strain parameters through finite element method. The impact of three stent designs (Palmaz–Schatz stent, Express stent, and Multilink Vision stent) on the arterial stress distributions were characterized. The influences of initial stent deployment location, stent-tissue friction, and plaque properties on the arterial stresses were also investigated. Higher arterial stresses were observed at the proximal end of the plaque. The Multilink–Vision stent induced lesser stress concentrations due to the high stiffness of the Cobalt Chromium material and thinner strut thickness. The stent-induced arterial stress concentrations were positively correlated with the reported in-stent restenosis rates, with a correlation coefficient of 0.992. Stent deployment initiated at the center of the lumen led to less arterial stress variation, while deployment closer to the thinner edge of the plaque causes higher arterial stresses. The friction between the stent and tissue was found to contribute to larger stress alternations for the plaque only. Increased plaque stiffness resulted in a reduced arterial stress concentration and clinical restenosis rate. Results presented herein suggested that arterial stresses serve as a comprehensive index factor to predict the occurrence of in-stent restenosis, which will facilitate the new stent design and surgical planning.
UNSTEADY BLOOD FLOW IN AN ARTERY WITH AN OVERLAPPING STENOSIS
Authors: RIAHI DANIEL N. , ROY RANADHIR
Published: April 2012

We consider the problem of unsteady blood flow in an artery and in the presence of an overlapping symmetric stenosis. The blood flow in the arterial tube is assumed to be a suspension of red cells in plasma. The present formulation makes use of the variable fluid viscosity modeling that takes into account the amount of the red cells in the blood fluid flow system. Using both analytical and computational methods, we determine the expression for various quantities such as the leading order flow velocity, pressure gradient, impedance and shear stress at the throats and at the critical height, and we calculate dependence of these quantities on the temporal and spatial variables as well as on the frequency of the flow oscillation and the main parameters of the flow system. We find, in particular, that the higher value of the frequency can lead to higher values of the magnitude for the quantities such as the axial velocity, the impedance and the wall shear stress in the stenosis zone particularly if the stenosis is less mild.
EVALUATING DOT-LEAD COUPLING IN A NONPARABOLIC QUANTUM DOT CONNECTED TO TWO CONDUCTING LEADS
Authors: GRADO-CAFFARO M. A. , GRADO-CAFFARO M.
Published: April 2012

By considering excitons in a semiconductor nonparabolic quantum dot as hydrogen-atom-like quasi-particles confined in a spherical quantum box, the dot being connected to two semi-infinite conducting leads, we propose a theoretical-analytical approach by which the maximal dot-lead coupling energy is calculated in terms of the maximum Fermi velocity. In addition, numerical computations consistent with the above approach are carried out. Our results constitute a deep insight into the state of the art and agree with experimental data.
IN SITU FABRICATION OF HIGH PERFORMANCE POLYIMIDE/TYROSINE-MODIFIED LAYERED SILICATE NANOCOMPOSITES
Authors: MALLAKPOUR SHADPOUR , DINARI MOHAMMAD
Published: April 2012

Several novel organic–inorganic hybrids consisting of high performance polyimide (PI) and organically modified montmorillonite (OMMT) with trifunctional swelling agent were successfully prepared by in situ polymerization technique. In this way, at first, OMMT was prepared by surface treatment of Cloisite Na+ with protonated form of bioactive L-tyrosine amino acid. Amine functional groups of this swelling agent formed an ionic bond with the negatively charged silicates, whereas the remaining acidic and phenolic functional groups are available for further interaction with PI chains. Then, organo-soluble PI with benzimidazole pendent group was prepared from pyromellitic dianhydride and 4-(3, 5-diaminophenyl)-benzimidazole in dry N,N-dimethylacetamide. PI/OMMT nanocomposites enclosing 1–10 wt.% of OMMT were successfully prepared by an in situ polymerization reaction through thermal imidization up to 300°C. Also, the relationship between the properties and OMMT content of the PI hybrid films were examined using Fourier-transform infrared spectroscopy, X-ray diffraction measurements and electronic microscopy (FE-SEM and TEM). The silicate layers in the polymer matrix were exfoliated as confirmed by XRD, FE-SEM and TEM techniques. The PI/OMMT films have good optical transparencies, and are almost colorless. The thermal stability of hybrids such as the decomposition temperature and weight residue at 800°C were also increased with increasing OMMT content.
COMPUTING THE TAXONOMIC, MORPHOLOGICAL AND SEXUAL VARIATIONS OF BORNEAN HORNBILLS (FAMILY: BUCEROTIDAE)
Authors: LAMAN CHARLIE J. M. , KHO ANGEL
Published: April 2012

Bornean Hornbills (Family Bucerotidae) are omnivorous creatures, distinguished for their large size and large bill. In our study, only five out of eight species of Bornean hornbills were available. Our aims were to determine the taxonomic, morphological and sexual variations, among the species. Nine morphological features were measured from 83 specimens. Canonical Discriminant and Cluster analyses showed that the data were successfully clustered into 5 species. Logistic regression analyses showed that the diagnostic character differentiation is total length. Further results showed that males tend to be bigger than females.
NONLINEAR CONFORMATION OF SECONDARY PROTEIN FOLDING
Authors: JANUAR M. , SULAIMAN A. , HANDOKO L.T.
Published: April 2012

A model to describe the mechanism of conformational dynamics in secondary protein based on matter interactions is proposed. The approach deploys the lagrangian method by imposing certain symmetry breaking. The protein backbone is initially assumed to be nonlinear and represented by the Sine-Gordon equation, while the nonlinear external bosonic sources is represented by ϕ4 interaction. It is argued that the nonlinear source induces the folding pathway in a different way than the previous work with initially linear backbone. Also, the nonlinearity of protein backbone decreases the folding speed.
MODELING THE INTERACTIONS OF BIOMATTER AND BIOFLUID
Authors: SULAIMAN A. , HANDOKO L.T.
Published: April 2012

The internal motions of biomatter immersed in biofluid are investigated. The interactions between the fragments of biomatter and its surrounding biofluid are modeled using field theory. In the model, the biomatter is coupled to the gauge field representing the biofluid. It is shown that at non-relativistic limit various equation of motions, from the well-known Sine-Gordon equation to the simultaneous nonlinear equations, can be reproduced within a single framework.
ON DYNAMICS OF ξS QUADRATIC STOCHASTIC OPERATORS
Authors: MUKHAMEDOV FARRUKH , SABUROV MANSOOR , JAMAL AFIFAH HANUM MOHD
Published: April 2012

In this research we introduce a new class of quadratic stochastic operators called ξ s -QSO which are defined through coefficient of the operator from measure-theoretic (namely we are looking the coefficient as the measures which are absolute continuous or singular) point of view. We also study the limiting behaviour of ξ s -QSO defined on 2D-simplex. We first describe ξ s -QSO on 2D-simplex and classify them with respect to the conjugacy and renumeration of the coordinates. We find six non-isomorphic classes of such operators. Moreover, we investigate the behaviour of each operator from three classes and prove convergence of trajectories of these classes and study their certain properties. We showed trajectories of two classes converge to the equilibrium. For the third class, it is established only the negative trajectories converge to the equilibrium.
AN ACCURATE SOLUTION TO THE LOTKA-VOLTERRA EQUATIONS BY MODIFIED HOMOTOPY PERTURBATION METHOD
Authors: CHOWDHURY M. S. H. , RAHMAN M. M.
Published: April 2012

In this paper, we suggest a method to solve the multispecies Lotka-Voltera equations. The suggested method, which we call modified homotopy perturbation method, can be considered as an extension of the homotopy perturbation method (HPM) which is very efficient in solving a varety of differential and algebraic equations. The HPM is modified in order to obtain the approximate solutions of Lotka-Voltera equation response in a sequence of time intervals. In particular, the example of two species is considered. The accuracy of this method is examined by comparison with the numerical solution of the Runge-Kutta-Verner method. The results prove that the modified HPM is a powerful tool for the solution of nonlinear equations.
A GENETIC ALGORITHM BASED ON SEXUAL SELECTION FOR THE MULTIDIMENSIONAL 0/1 KNAPSACK PROBLEMS
Authors: VARNAMKHASTI MOHAMMAD JALALI , LEE LAI SOON
Published: April 2012

In this study, a new technique is presented for choosing mate chromosomes during sexual selection in a genetic algorithm. The population is divided into groups of males and females. During the sexual selection, the female chromosome is selected by the tournament selection while the male chromosome is selected based on the hamming distance from the selected female chromosome, fitness value or active genes. Computational experiments are conducted on the proposed technique and the results are compared with some selection mechanisms commonly used for solving multidimensional 0/1 knapsack problems published in the literature.
NUMERICAL SOLUTION FOR SOLVING SECOND ORDER ORDINARY DIFFERENTIAL EQUATIONS USING BLOCK METHOD
Authors: MUKHTAR NUR ZAHIDAH , MAJID ZANARIAH ABDUL , ISMAIL FUDZIAH , SULEIMAN MOHAMED
Published: April 2012

The purpose of this paper is to present a four point direct block one-step method for solving directly the general second order nonstiff initial value problems (IVPs) of ordinary differential equations (ODEs). The mathematical problems in real world can be written in the form of differential equations and arise in the fields of science and engineering such as fluid dynamic, electric circuit, motion of rocket or satellite and other area of application. The proposed method will estimate the approximation solutions at four points simultaneously by using variable step size. Numerical results are given to show the efficiency of the proposed method.
Nuclear Hormone Receptors Enable Macrophages and Dendritic Cells to Sense Their Lipid Environment and Shape Their Immune Response
Authors: Nagy Laszlo , Szanto Attila , Szatmari Istvan , Széles Lajos
Published: April 2012

A key issue in the immune system is to generate specific cell types, often with opposing activities. The mechanisms of differentiation and subtype specification of immune cells such as macrophages and dendritic cells are critical to understand the regulatory principles and logic of the immune system. In addition to cytokines and pathogens, it is increasingly appreciated that lipid signaling also has a key role in differentiation and subtype specification. In this review we explore how intracellular lipid signaling via a set of transcription factors regulates cellular differentiation, subtype specification, and immune as well as metabolic homeostasis. We introduce macrophages and dendritic cells and then we focus on a group of transcription factors, nuclear receptors, which regulate gene expression upon receiving lipid signals. The receptors we cover are the ones with a recognized physiological function in these cell types and ones which heterodimerize with the retinoid X receptor. These are as follows: the receptor for a metabolite of vitamin A, retinoic acid: retinoic acid receptor (RAR), the vitamin D receptor (VDR), the fatty acid receptor: peroxisome proliferator-activated receptor γ (PPARγ), the oxysterol receptor liver X receptor (LXR), and their obligate heterodimeric partner, the retinoid X receptor (RXR). We discuss how they can get activated and how ligand is generated and eliminated in these cell types. We also explore how activation of a particular target gene contributes to biological functions and how the regulation of individual target genes adds up to the coordination of gene networks. It appears that RXR heterodimeric nuclear receptors provide these cells with a coordinated and interrelated network of transcriptional regulators for interpreting the lipid milieu and the metabolic changes to bring about gene expression changes leading to subtype and functional specification. We also show that these networks are implicated in various immune diseases and are amenable to therapeutic exploitation.
A Molecular Imaging Primer: Modalities, Imaging Agents, and Applications
Authors: James Michelle L. , Gambhir Sanjiv S.
Published: April 2012

Molecular imaging is revolutionizing the way we study the inner workings of the human body, diagnose diseases, approach drug design, and assess therapies. The field as a whole is making possible the visualization of complex biochemical processes involved in normal physiology and disease states, in real time, in living cells, tissues, and intact subjects. In this review, we focus specifically on molecular imaging of intact living subjects. We provide a basic primer for those who are new to molecular imaging, and a resource for those involved in the field. We begin by describing classical molecular imaging techniques together with their key strengths and limitations, after which we introduce some of the latest emerging imaging modalities. We provide an overview of the main classes of molecular imaging agents (i.e., small molecules, peptides, aptamers, engineered proteins, and nanoparticles) and cite examples of how molecular imaging is being applied in oncology, neuroscience, cardiology, gene therapy, cell tracking, and theranostics (therapy combined with diagnostics). A step-by-step guide to answering biological and/or clinical questions using the tools of molecular imaging is also provided. We conclude by discussing the grand challenges of the field, its future directions, and enormous potential for further impacting how we approach research and medicine.
Validity and Reproducibility of the Measurements Obtained Using the Flexicurve Instrument to Evaluate the Angles of Thoracic and Lumbar Curvatures of the Spine in the Sagittal Plane
Authors: de Oliveira Tatiana Scheeren , Candotti Cláudia Tarragô , La Torre Marcelo , Pelinson Patricia Paula Tonin , Furlanetto Tássia Silveira , Kutchak Fernanda Machado , Loss Jefferson Fagundes
Published: April 2012

Objective. to verify the validity and reproducibility of using the flexicurve to measure the angles of the thoracic and lumbar curvatures.Method. 47 subjects were evaluated by: (1) palpation and marking of the spinous processes using lead markers, (2) using X-rays in the sagittal plane to measure the Cobb angles, (3) molding the flexicurve to the spine, and (4) drawing the contour of the flexicurve onto graph paper. The angle of curvature was determined with the flexicurve based on a 3rd order polynomial.Results. No differences were found between the Cobb angles and the angles obtained using the flexicurve in thoracic and lumbar curvatures (). Correlations were strong and significant for the thoracic (, ) and lumbar (, ) curvatures. Excellent and significant correlations were found for both the intraevaluator and interevaluator measurements.Conclusion. The results show that there is no significant difference between the values obtained using the flexicurve and those obtained using the X-ray procedure and that there is a strong correlation between the two methods. This, together with the excellent level of inter- and intraevaluator reproducibility justifies its recommendation for use in clinical practice.
Uterine Healing after Therapeutic Intrauterine Administration of TachoSil (Hemostatic Fleece) in Cesarean Section with Postpartum Hemorrhage Caused by Placenta Previa
Authors: Fuglsang Katrine , Dueholm Margit , Stæhr-Hansen Estrid , Petersen Lone Kjeld
Published: April 2012

Background. Application of hemostatic fleece (TachoSil) directly onto the bleeding surfaces of the lower uterine segment has been used to obtain hemostasis during cesarean section caused by placenta previa.Methods. Eleven of 15 patients treated with TachoSil for excessive postpartum haemorrhage due to placenta previa were enrolled. An evaluation of the cesarean section scar by transvaginal ultrasound, the uterine cavity and endometrium by hysteroscopy, and the endometrium by biopsy were made. The main outcome measures were intrauterine adhesions, recovery of endometrium at the site of TachoSil application, visible remnants of TachoSil, and scar healing.Results. Eight patients had small remnants of TachoSil in the uterine cavity together with signs of resorption. All had a normal endometrial mucosa, and none had adhesions in the uterine cavity. All cesarean section scars were healed without defects.Conclusion. TachoSil did not seem to impair healing of the endometrium or scar formation in the uterus after intrauterine application. Resorption of TachoSil seems to progress individually. Intrauterine treatment with TachoSil is a valuable supplement to the traditional treatment of post partum haemorrhage and may help retain reproductive capability. This is a small study, and it will require more studies to confirm the reproducibility.
Hidden‐Markov‐Models‐Based Dynamic Hand Gesture Recognition
Authors: Wang Xiaoyan , Xia Ming , Cai Huiwen , Gao Yong , Cattani Carlo
Published: April 2012

This paper is concerned with the recognition of dynamic hand
gestures. A method based on Hidden Markov Models (HMMs) is presented
for dynamic gesture trajectory modeling and recognition. Adaboost
algorithm is used to detect the user′s hand and a contour‐based hand
tracker is formed combining condensation and partitioned sampling.
Cubic B‐spline is adopted to approximately fit the trajectory points
into a curve. Invariant curve moments as global features and
orientation as local features are computed to represent the
trajectory of hand gesture. The proposed method can achieve
automatic hand gesture online recognition and can successfully
reject atypical gestures. The experimental results show that the
proposed algorithm can reach better recognition results than the
traditional hand recognition method.
Oncology in Cambodia
Authors: Eav S. , Schraub S. , Dufour P. , Taisant D. , Ra C. , Bunda P.
Published: April 2012

Cambodia, a country of 14 million inhabitants, was devastated during the Khmer Rouge period and thereafter. The resources of treatment are rare: only one radiotherapy department, renovated in 2003, with an old cobalt machine; few surgeons trained to operate on cancer patients; no hematology; no facilities to use intensive chemotherapy; no nuclear medicine department and no palliative care unit. Cervical cancer incidence is one of the highest in the world, while in men liver cancer ranks first (20% of all male cancers). Cancers are seen at stage 3 or 4 for 70% of patients. There is no prevention program – only a vaccination program against hepatitis B for newborns – and no screening program for cervical cancer or breast cancer. In 2010, oncology, recognized as a full specialty, was created to train the future oncologists on site at the University of Phnom Penh. A new National Cancer Center will be built in 2013 with modern facilities for radiotherapy, medical oncology, hematology and nuclear medicine. Cooperation with foreign countries, especially France, and international organizations has been established and is ongoing. Progress is occurring slowly due to the shortage of money for Cambodian institutions and the lay public.
Gardnerella, Trichomonas and Candida in Cervical Smears of 58,904 Immigrants Participating in the Dutch National Cervical Screening Program
Authors: Boon Mathilde E. , Holloway Penny A. , Breijer Hanna , Bontekoe T. Romke
Published: April 2012

Objective: To report the prevalence of Gardnerella, Trichomonas and Candida in the cervical smears of 9 immigrant groups participating in the Dutch national cervical screening program. Study Design: Cervical smears were taken from 58,904 immigrant participants and 498,405 Dutch participants. As part of the routine screening process, all smears were screened for the overgrowth of Gardnerella (i.e. smears with an abundance of clue cells) and for the presence of Trichomonas and Candida. The smears were screened by 6 laboratories, all of which use the Dutch KOPAC coding system. The odds ratio and confidence interval were calculated for the 9 immigrant groups and compared to Dutch participants. Results: Immigrants from Suriname, Turkey and the Dutch Antilles have a 2–5 times higher prevalence of Gardnerella and Trichomonas when compared to native Dutch women. Interestingly, the prevalence of Trichomonas in cervical smears of Moroccan immigrants is twice as high, yet the prevalence of Gardnerella is 3 times lower than in native Dutch women. Conclusions: Immigrants with a high prevalence of Gardnerella also have a high prevalence of Trichomonas. In the context of the increased risk of squamous abnormalities in smears with Gardnerella, such slides should be screened with extra care.
EEG Vigilance Regulation Patterns and Their Discriminative Power to Separate Patients with Major Depression from Healthy Controls
Authors: Olbrich Sebastian , Sander Christian , Minkwitz Juliane , Chittka Tobias , Mergl Roland , Hegerl Ulrich , Himmerich Hubertus
Published: April 2012

Background/Aim: Recently, a framework has been presented that links vigilance regulation, i.e. tonic brain arousal, with clinical symptoms of affective disorders. Against this background, the aim of this study was to deepen the knowledge of vigilance regulation by (1) identifying different patterns of vigilance regulation at rest in healthy subjects (n = 141) and (2) comparing the frequency distribution of these patterns between unmedicated patients with major depression (MD; n = 30) and healthy controls (HCs; n = 30). Method: Each 1-second segment of 15-min resting EEGs from 141 healthy subjects was classified as 1 of 7 different vigilance stages using the Vigilance Algorithm Leipzig. K-means clustering was used to distinguish different patterns of EEG vigilance regulation. The frequency distribution of these patterns was analyzed in independent data of 30 unmedicated MD patients and 30 matched HCs using a χ2 test. Results: The 3-cluster solution with a stable, a slowly declining and an unstable vigilance regulation pattern yielded the highest mathematical quality and performed best for separation of MD patients and HCs (χ2 = 13.34; p < 0.001). Patterns with stable vigilance regulation were found significantly more often in patients with MD than in HCs. Conclusion: A stable vigilance regulation pattern, derived from a large sample of HCs, characterizes most patients with MD and separates them from matched HCs with a sensitivity between 67 and 73% and a specificity between 67 and 80%. The pattern of vigilance regulation might be a useful biomarker for delineating MD subgroups, e.g. for treatment prediction.
Significance of Virchow-Robin Spaces in Patients Newly Diagnosed with Multiple Sclerosis: A Case-Control Study in an Arab Population
Authors: Al-Saeed Osama , Athyal Reji , Ismail Mohammed , Sheikh Mehraj
Published: April 2012

Objective: To assess the frequency and extent of dilatation of Virchow-Robin (VR) spaces at three levels of the brain in patients of Arab ethnicity in Kuwait recently diagnosed with multiple sclerosis (MS) and compare the results with age- and gender-matched controls. Methods: The magnetic resonance imaging (MRI) scans performed within 3 months of the clinical diagnosis of 80 patients recently diagnosed with active MS were compared to those of 80 age- and gender-matched controls with headache but without any neurological deficits for the frequency and size of VR spaces. MRI was done with noncontrast axial and coronal T1W FSE, axial T2W FSE, axial T2W FLAIR and sagittal FLAIR sequences followed by postcontrast axial and coronal T1W sequences. The frequency of VR spaces in MS patients and controls at midbrain, lenticulostriate vessels and supraventricular levels was analyzed using a two-tailed McNemar test. Results: There was no difference in the frequency of VR spaces at the levels of the midbrain, lenticulostriate vessels and supraventricular white matter between MS patients and controls. In the supraventricular region, however, there were 91 dilated VR spaces in 26 (32%) of the MS patients while in the control group, there were 8 dilated VR spaces in 6 (7.5%) patients and the difference was statistically significant (p < 0.0001). Conclusion: The data showed that dilated VR spaces in the supraventricular region could potentially be used as a marker for MS and as a prognostic tool. However, further studies with a larger population are needed to further evaluate and confirm this observation.
Interaction of Alfaxalone with the Neuronal and the Skeletal Muscle Sodium Channel
Authors: Foadi Nilufar , Pilawski Igor , Buchholz Vanessa , de la Roche Jeanne , Wegner Florian , Leffler Andreas , Ahrens Jörg , Kästner Sabine
Published: April 2012

The neurosteroid alfaxalone exerts potent anesthetic activity in humans and animals. In former studies on myelinated axons, alfaxalone was assumed to produce a local anesthetic-like effect on the peripheral nervous system. Therefore, the present in vitro study aimed to characterize possible modulatory actions of alfaxalone on voltage-gated sodium channels. α-Subunits of voltage-gated neuronal (Nav1.2) and skeletal muscle (Nav1.4) sodium channels were stably expressed in human embryonic kidney cells, and in vitro effects of alfaxalone were compared with lidocaine by means of the patch clamp technique. Alfaxalone preferentially blocked slow inactivated channels and therefore could provide membrane-stabilizing effects in ischemic/hypoxic tissues where slow inactivation is regarded to play a crucial role.
Fetal and Maternal Analgesia/Anesthesia for Fetal Procedures
Authors: van de Velde Marc , De Buck Frederik
Published: April 2012

For many prenatally diagnosed conditions, treatment is possible before birth. These fetal procedures can range from minimal invasive punctions to full open fetal surgery. Providing anesthesia for these procedures is a challenge, where care has to be taken for both mother and fetus. There are specific physiologic changes that occur with pregnancy that have an impact on the anesthetic management of the mother. When providing maternal anesthesia, there is also an impact on the fetus, with concerns for potential negative side effects of the anesthetic regimen used. The question whether the fetus is capable of feeling pain is difficult to answer, but there are indications that nociceptive stimuli have a physiologic reaction. This nociceptive stimulation of the fetus also has the potential for longer-term effects, so there is a need for fetal analgesic treatment. The extent to which a fetus is influenced by the maternal anesthesia depends on the type of anesthesia, with different needs for extra fetal anesthesia or analgesia. When providing fetal anesthesia, the potential negative consequences have to be balanced against the intended benefits of blocking the physiologic fetal responses to nociceptive stimulation.
Linear versus Nonlinear Filtering with Scale-Selective Corrections for Balanced Dynamics in a Simple Atmospheric Model
Authors: Subramanian Aneesh C. , Hoteit Ibrahim , Cornuelle Bruce , Miller Arthur J. , Song Hajoon
Published: April 2012

This paper investigates the role of the linear analysis step of the ensemble Kalman filters (EnKF) in disrupting the balanced dynamics in a simple atmospheric model and compares it to a fully nonlinear particle-based filter (PF). The filters have a very similar forecast step but the analysis step of the PF solves the full Bayesian filtering problem while the EnKF analysis only applies to Gaussian distributions. The EnKF is compared to two flavors of the particle filter with different sampling strategies, the sequential importance resampling filter (SIRF) and the sequential kernel resampling filter (SKRF). The model admits a chaotic vortical mode coupled to a comparatively fast gravity wave mode. It can also be configured either to evolve on a so-called slow manifold, where the fast motion is suppressed, or such that the fast-varying variables are diagnosed from the slow-varying variables as slaved modes. Identical twin experiments show that EnKF and PF capture the variables on the slow manifold well as the dynamics is very stable. PFs, especially the SKRF, capture slaved modes better than the EnKF, implying that a full Bayesian analysis estimates the nonlinear model variables better. The PFs perform significantly better in the fully coupled nonlinear model where fast and slow variables modulate each other. This suggests that the analysis step in the PFs maintains the balance in both variables much better than the EnKF. It is also shown that increasing the ensemble size generally improves the performance of the PFs but has less impact on the EnKF after a sufficient number of members have been used.
Intraseasonal Tropical Atmospheric Variability Associated with the Two Flavors of El Niño
Authors: Gushchina Daria , Dewitte Boris
Published: April 2012

The characteristics of intraseasonal tropical variability (ITV) associated with the two flavors of El Niño [i.e., the canonical or eastern Pacific (EP) El Niño and the Modoki or central Pacific (CP) El Niño] are documented using composite and regression analysis. Double space–time Fourier analysis is applied to the NCEP–NCAR zonal wind at 850 hPa (U850) to separate the different components of the ITV in the tropical troposphere, which is then used to define indices of wave activity, and document the spatial pattern of the waves.

It is shown that the ITV characteristics are altered during CP El Niño compared to the typical seasonal dependence of the ITV–ENSO relationship. In particular, while EP El Niño is characterized by enhanced MJO and equatorial Rossby (ER) wave activity during spring–summer prior to the ENSO peak, during CP El Niño, the ITV activity is increased during the mature and decaying phases. It is suggested that ITV is more propitious to the triggering of the EP event; while during the CP event, it contributes mostly to the persistence of positive SST anomalies. The oceanic response of these ITV anomalous patterns is further investigated in the Simple Ocean Data Assimilation (SODA) reanalysis by documenting the seasonal evolution of the intraseasonal equatorial oceanic Kelvin wave (IEKW) activity during the two flavors of El Niño. It is shown that anomalous westerlies associated with ITV may generate the corresponding response in the ocean in the form of anomalous IEKW activity.
Cerebral Vasculopathy in Children With Neurofibromatosis Type 1
Authors: Ghosh Partha S. , Rothner A. David , Emch Todd M. , Friedman Neil R. , Moodley Manikum
Published: April 2012

Cerebral vasculopathy is an important but underrecognized complication of neurofibromatosis type 1. Over a 10-year period, we retrospectively assessed the prevalence, clinical manifestations, management, and outcome of cerebral vasculopathy in children with neurofibromatosis type 1. Magnetic resonance imaging (MRI) of the brain was performed on 78% of the patients (312/398) of which 46% (143/312) had magnetic resonance angiography of the intracranial arteries; 4.8% (15/312) had cerebral vasculopathy. Approximately half were asymptomatic at presentation; none had neurologic deficits. Cerebral vasculopathy included moyamoya changes (7) and stenosis/occlusion of major intracranial arteries (8). On follow-up (mean 4 years), 2 patients developed radiologic progression; 1 was treated with aspirin alone, whereas another underwent revascularization surgery. Although cerebral vasculopathy in neurofibromatosis type 1 may be asymptomatic at presentation, there may be radiologic and clinical progression leading to morbidity and mortality. Magnetic resonance angiography should be considered with brain MRI for early detection and timely intervention of cerebral vasculopathy.
No Such Thing as a “Blind Culture”
Authors: Weisleder Pedro
Published: April 2012

Cochlear implant technology has altered the landscape for the Deaf and for those who provide services to the profoundly hearing impaired. As indicated by Teagle in one of the companion articles, cochlear implants afford the profoundly hearing impaired child the ability to circumvent the effects of deafness. Cochlear implants, as indicated by Lee in the other companion article, are regarded differently by members of the Deaf Community where some see the technology as a threat to Deaf Culture. Members of a different community, which comprises the visually impaired, cite lack of a common language as the main argument against the existence of a “Blind Culture.” As indicated by Pierce “We [the blind] often enjoy each other's company, and we certainly spend time together working on the problems that face what we often call the ‘blind community,’ but I would argue that this community is different from an actual culture.”
Curcumin and resveratrol in combination modulates benzo(a)pyrene-induced genotoxicity during lung carcinogenesis
Authors: Malhotra A , Nair P , Dhawan DK
Published: April 2012

The present study attempted to explore the efficacy of curcumin and resveratrol in modulating mitotic catastrophe and apoptosis during lung carcinogenesis. The mice were segregated into five groups, which included normal control, benzo(a)pyrene (BP)-treated, BP + curcumin (C)-treated, BP + resveratrol (R)-treated and BP + C + R-treated groups. The BP treatment resulted in a significant increase in the formation of micronuclei as well as in the protein expression of bcl-2 in the lungs of mice. On the other hand, a significant decrease was observed in the number of apoptotic cells and protein expression of bax in the lungs of BP-treated mice. Supplementation of curcumin and resveratrol individually to BP-treated animals resulted in a decrease in the micronuclei formation; however, it was not statistically significant. Interestingly, combination of curcumin and resveratrol resulted in a statistically significant decrease in micronuclei formation. Moreover, phytochemicals in combination significantly reduced the protein expression of bcl-2 in BP-treated mice. Furthermore, supplementation of phytochemicals in combination brought a noticeable improvement in the number of apoptotic cells as well as in the protein expression of bax. The present study, therefore, concludes that the combined treatment with curcumin and resveratrol modulates mitotic catastrophe by stimulating apoptosis in BP-treated mice.
Depressive Symptoms and Diurnal Salivary Cortisol Patterns Among Female Caregivers of Stroke Survivors
Authors: Saban Karen L. , Mathews Herbert L. , Bryant Fred B. , O’Brien Timothy E. , Janusek Linda Witek
Published: April 2012

Informal caregivers of stroke survivors experience elevated chronic stress and are at risk of developing depressive symptoms. The cumulative effects of chronic stress can increase allostatic load and dysregulate biological processes, thus increasing risk of stress-related disease. Stress-induced alterations in the pattern of cortisol secretion vary with respect to stressor onset, intensity, and chronicity. Little is known about the psychoendocrine response to stress in female caregivers of stroke survivors. The purpose of this study was to examine perceived stress, caregiver burden, and the association between caregiver depressive symptoms and diurnal cortisol in 45 females caring for a significant other who experienced a stroke within the past year. Women completed the Center for Epidemiologic Studies Depression Scale (CES-D) and collected saliva for cortisol upon awakening, 30 min postawakening, noon, and bedtime for 2 consecutive days. Results revealed that women had high levels of perceived stress and caregiver burden. In women with CES-D scores ≥ 16, salivary cortisol levels were significantly lower across the day relative to women with CES-D scores < 16. This difference persisted after adjusting for age, number of caregiving hours per week, perceived social support, and quality of sleep. Younger age was associated with more depressive symptoms as well as lower levels of cortisol at awakening and 30 min postawakening. Results demonstrate that the burden of caregiving increases risk of depressive symptoms and hypocortisolism across the day. Hypocortisolism may contribute to increased risk of depressive symptoms as a result of the loss of glucocorticoid attenuation of stress-induced inflammation.
The impact of pretransplant 25-hydroxy vitamin D deficiency on subsequent graft function: An observational study
Authors: Kim Hyunwook , Kang Shin-Wook , Yoo Tae-Hyun , Kim Myoung Soo , Kim Soon Il , Kim Yu Seun , Choi Kyu Hun
Published: April 2012

Background

In addition to its canonical role in musculoskeletal health, several reports have demonstrated that serum vitamin D level may influence kidney function. However, the effect of pretransplant serum vitamin D level on subsequent graft function has not been explored. Therefore, this study was undertaken to examine the effect of serum vitamin D level at the time of kidney transplantation (KT) on subsequent graft function.

Methods

We analyzed 106 patients who underwent KT and for whom 25-hydroxy vitamin D (25-OHD) levels were measured during hospitalization prior to transplantation. We measured estimated glomerular filtration rates (eGFR) using the Modification of Diet in Renal Disease (MDRD) formula at baseline and at six-month intervals up to 36 months after KT.

Results

38.7% of the patients were diagnosed with 25-OHD deficiency defined as less than 10 ng/mL. Recipient gender (female vs. male, odds ratio [OR] 3.30, 95% CI 1.33-8.21,P= 0.010), serum albumin level (per 1 mg/dl increase, OR 0.35, 95% CI 0.13-0.98,P= 0.047), and predominant renal replacement therapy modality before KT (P< 0.001) were found to be independent pretransplant risk factors for 25-OHD deficiency by multivariate logistic regression analysis. Subsequent repeated measures analysis of covariance revealed that 25-OHD level had the only significant main effect on eGFR during the 36-month follow-up period [F(1, 88) = 12.07,P= 0.001].

Conclusions

Pretransplant 25-OHD deficiency was significantly associated with a lower post-transplant eGFR, suggesting that 25-OHD may play an important role in maintaining graft function after KT.
Non-physician providers of obstetric care in Mexico: Perspectives of physicians, obstetric nurses and professional midwives
Authors: DeMaria Lisa M , Campero Lourdes , Vidler Marianne , Walker Dilys
Published: April 2012

Background

In Mexico 87% of births are attended by physicians. However, the decline in the national maternal mortality rate has been slower than expected. The Mexican Ministry of Health’s 2009 strategy to reduce maternal mortality gives a role to two non-physician models that meet criteria for skilled attendants: obstetric nurses and professional midwives. This study compares and contrasts these two provider types with the medical model, analyzing perspectives on their respective training, scope of practice, and also their perception and/or experiences with integration into the public system as skilled birth attendants.

Methodology

This paper synthesizes qualitative research that was obtained as a component of the quantitative and qualitative study that evaluated three models of obstetric care: professional midwives (PM), obstetric nurses (ON) and general physicians (GP). A total of 27 individual interviews using a semi-structured guide were carried out with PMs, ONs, GPs and specialists. Interviews were transcribed following the principles of grounded theory, codes and categories were created as they emerged from the data. We analyzed data in ATLAS.ti.

Results

All provider types interviewed expressed confidence in their professional training and acknowledge that both professional midwives and obstetric nurses have the necessary skills and knowledge to care for women during normal pregnancy and childbirth. The three types of providers recognize limits to their practice, namely in the area of managing complications.

We found differences in how each type of practitioner perceived the concept and process of birth and their role in this process. The barriers to incorporation as a model to attend birth faced by PMs and ONs are at the individual, hospital and system level. GPs question their ability and training to handle deliveries, in particular those that become complicated, and the professional midwifery model particularly as it relates to a clinical setting, is also questioned.

Conclusions

Hospitals in the Mexican public health sector have a heavy obstetric workload; physicians carry the additional burden of non-obstetric cases. The incorporation of a non- physician model at the primary health center level to attend low-risk, normal deliveries would contribute to the reduction of non-necessary referrals. There is also a role for these providers at the hospital level.