bluuebunny/crossref_metadata_2025 huggingface dataset:
Trends in paediatric airway surgery: a move towards endoscopic techniques
Authors: De S , Bailey C M
Published: December 2009

The endoscope has long been an invaluable tool in assessment of the paediatric airway. Recently, its applications for definitive surgery of the airway have greatly increased, due to innovative surgical techniques, development of new instruments, improvements in anaesthesia and availability of new medications for endoscopic use. This review discusses the move towards endoscopic techniques in the management of paediatric airway disorders.
Structure–functional intimacies of transient receptor potential channels
Authors: Latorre Ramon , Zaelzer Cristián , Brauchi Sebastian
Published: December 2009

Although a unifying characteristic common to all transient receptor potential (TRP) channel functions remains elusive, they could be described as tetramers formed by subunits with six transmembrane domains and containing cation-selective pores, which in several cases show high calcium permeability. TRP channels constitute a large superfamily of ion channels, and can be grouped into seven subfamilies based on their amino acid sequence homology: the canonical or classic TRPs, the vanilloid receptor TRPs, the melastatin or long TRPs, ankyrin (whose only member is the transmembrane protein 1 [TRPA1]), TRPN after the nonmechanoreceptor potential C (nonpC), and the more distant cousins, the polycystins and mucolipins. Because of their role as cellular sensors, polymodal activation and gating properties, many TRP channels are activated by a variety of different stimuli and function as signal integrators. Thus, how TRP channels function and how function relates to given structural determinants contained in the channel-forming protein has attracted the attention of biophysicists as well as molecular and cell biologists. The main purpose of this review is to summarize our present knowledge on the structure of channels of the TRP ion channel family. In the absence of crystal structure information for a complete TRP channel, we will describe important protein domains present in TRP channels, structure–function mutagenesis studies, the few crystal structures available for some TRP channel modules, and the recent determination of some TRP channel structures using electron microscopy.
Consequentialism without Consequences: Ethics and Embryo Research
Authors: CHAN SARAH , HARRIS JOHN
Published: December 2009

The legitimacy of embryo research, use, and destruction is among the most important issues facing contemporary bioethics. In the preceding paper, Ingmar Persson and Julian Savulescu took up an argument of John Harris and tried to find some new ways of avoiding its dramatic consequences. They noted that: “John Harris has argued that if … it is morally permissible to engage in reproduction … despite knowledge that a large number of embryos will fail to implant and quickly die, then … it is morally permissible to produce embryos for other purposes that involve killing them, for instance, to harvest stem cells” and suggest that this argument fails.
Visible and near‐infrared nightglow of molecular oxygen in the atmosphere of Venus
Authors: García Muñoz A. , Mills F. P. , Slanger T. G. , Piccioni G. , Drossart P.
Published: December 2009

The Herzberg II system of O2 has been a known feature of Venus' nightglow since the Venera 9 and 10 orbiters detected its c(0)–X(v″) progression more than 3 decades ago. We search for its emission at 400 nm–700 nm in spectra obtained with the VIRTIS instrument on Venus Express. Despite the weakness of the signal, integration over a few hours of limb observations of the planet's upper atmosphere reveals the unambiguous pattern of the progression. The selected data sample mainly the northern latitudes within a few hours of local midnight. The emission is ubiquitous on the nightside of Venus and can be discerned at tangent altitudes from 80 km to 110 km. The average emission vertical profiles of the c(0)–X(v″) progression and the O2a(0)–X(0) band, the latter from simultaneous near‐infrared spectra, are quite similar, with their respective peaks occurring within ±1 km of each other. We conclude that the net yield for production of the c(0) state is low, ∼1%–2% of the oxygen recombination rate, and that O(3P) and CO2 are the two likely quenchers of the Herzberg II nightglow, although CO cannot be ruled out. We also derive a value of 2.45 × 10−16 cm3 s−1 for the rate constant at which CO2 collisionally quenches the c(0) state. Our VIRTIS spectra show hints of O2A′(0)–a(v″) emission but no traces of the O (1S–1D) green line at 557.7 nm.
Magnetoelectric spin wave amplifier for spin wave logic circuits
Authors: Khitun Alexander , Nikonov Dmitri E. , Wang Kang L.
Published: December 2009

We propose and analyze a spin wave amplifier aimed to enhance the amplitude of the propagating spin wave via the magnetoelectric effect. The amplifier is a two-layer multiferroic structure, which comprises piezoelectric and ferromagnetic materials. By applying electric field to the piezoelectric layer, the stress is produced. In turn, the stress changes the direction of the easy axis in the ferromagnetic layer. The rotation frequency of the easy axis is the same as the frequency of the spin wave propagating through the ferromagnetic layer. As a result of this two-stage process, the amplitude of the spin wave can be amplified depending on the angle of the easy axis rotation. We present results of numerical simulations illustrating the operation of the proposed amplifier. According to numerical estimates, the amplitude of the spin wave signal can be increased by several orders of magnitude. The energy efficiency of the electric-to-magnetic power conversion is discussed. The proposed amplifier preserves the phase of the initial signal, which is important for application to logic circuits based on spin waves.
Emission wavelength tuning of interband cascade lasers in the 3–4 μm spectral range
Authors: Bauer A. , Langer F. , Dallner M. , Kamp M. , Motyka M. , Sęk G. , Ryczko K. , Misiewicz J. , Höfling S. , Forchel A.
Published: December 2009

GaSb-based type-II quantum well (QW) structures and interband cascade lasers (ICLs) are investigated with regards to the dependence of emission wavelength on active QW thicknesses. Experimentally derived photoluminescence data and electrically driven ICL device data accompanied by theoretical calculations yield an average tuning rate of 0.55 μm per monolayer InAs in the range between 2.97 and 4.16 μm. Together with a temperature dependent ICL tuning behavior of 1.88 nm/K, the presented results provide the means for reliable and accurate emission wavelength control of ICLs in the 3–4 μm wavelength span which is of major importance for gas sensing applications.
Characteristics of surface states and charge neutrality level in Ge
Authors: Kuzum Duygu , Martens Koen , Krishnamohan Tejas , Saraswat Krishna C.
Published: December 2009

The characteristics of surface states on Ge are investigated using metal/insulator/semiconductor structures and the conductance technique. Evidence of acceptor-like and donor-like surface states on the valence band side of the Ge bandgap is shown by trap time constant analysis. The dependency of trap time constants on trap energy separation from band edge, capture cross section, and temperature are studied through conductance measurements and simulations. The effect of surface states on the location of charge neutrality level at the Ge surface and the consequences such as surface conductivity and negative charge buildup at the interface are discussed.
Electrical, magnetic, magnetodielectric, and magnetoabsorption studies in multiferroic GaFeO3
Authors: Naik V. B. , Mahendiran R.
Published: December 2009

We report electrical, magnetic, magnetodielectric, and magnetoabsorption properties of a polycrystalline GaFeO3. The resistivity measurement shows that the sample is highly insulating below 200 K and the resistivity above 200 K obey the Arrhenius law with an activation energy of Ea=0.67 eV. An anomaly occurs in the temperature dependence of permittivity (ε) near the ferrimagnetic transition temperature (TC=228 K) in a zero magnetic field and it is suppressed under μ0H=60 mT which indicates a possible magnetoelectric coupling in GaFeO3 with a fractional change of Δε/ε=−1.8% at 60 mT around TC. The coercivity (HC) of the sample increases dramatically with lowering temperature below 200 K from 0.1 T at 200 K to 0.9 T at 5 K. Magnetoabsorption was studied with a LC resonance technique and we found a close correlation between the shift in the resonance frequency due to applied magnetic field and the coercive field measured using dc magnetization measurements. Our results obtained with multiple techniques suggest that GaFeO3 is an interesting ferrimagnet with potential applications in future multiferroic devices.
Modeling of metal-ferroelectric-insulator-semiconductor structures based on Langmuir–Blodgett copolymer films
Authors: Reece Timothy J. , Ducharme Stephen
Published: December 2009

Among the ferroelectric thin films used in field-effect transistor devices; the ferroelectric copolymer of polyvinylidene fluoride (PVDF) (–CH2–CF2–), with trifluoroethylene (TrFE) (–CHF–CF2–), has distinct advantages, including low dielectric constant, low processing temperature, low cost, and compatibility with organic semiconductors. The operation of a metal-ferroelectric-insulator-semiconductor structure with P(VDF-TrFE) as the ferroelectric layer was analyzed and optimized by numerical solution of the Miller and McWhorter model. A model device consisting of 20 nm PVDF/TrFE on a 10-nm-thick high-k dielectric buffer exhibits a memory window of 5 V with an operating voltage of ±15 V. The operating voltage can be reduced to ±12 V by reducing the ferroelectric and dielectric thicknesses to 10 and 5 nm, respectively.
Long-range exciton dissociation in layered organic solar cells
Authors: Song Qun Liang , Yang Hong Bin , Li Chang Ming
Published: December 2009

Long-range charge transfer in a donor-spacer-acceptor system is observed. When tris-8-hydroxy-quinolinato aluminum (Alq3) is used as a spacer between copper phthalocyanine (CuPc, donor) and C60 (acceptor), electron transfer over 14 nm from CuPc to C60 and hole transfer over 30 nm from C60 to CuPc occur. Two charge transfer mechanisms are identified by this study: electron tunneling via gap states of Alq3 (the lowest unoccupied molecular orbitals of Alq3 act as an energy barrier) and hole transport via the highest occupied molecular orbitals of Alq3, which act as step-stone levels. A thin spacer with suitable energy levels is suggested to improve the power conversion efficiency by inhibiting the recombination of geminate pair polarons.
Relaxation of the magnetization in uniaxial single-domain ferromagnetic particles driven by a strong ac magnetic field
Authors: Déjardin Pierre-Michel , Kalmykov Yuri P.
Published: December 2009

The magnetization spectrum and reversal time of uniaxial single-domain ferromagnetic particles driven by an ac magnetic field of arbitrary strength applied along the easy axis are evaluated by solving the infinite hierarchy of recurrence equations for the Fourier components of the relaxation functions governing the frequency dependence of the magnetization. A simple analytic equation for the reversal time is also obtained via the mean first passage time method exhibiting pronounced nonlinear effects such as a rapid decrease in the reversal time as the strength of the ac field increases. For weak ac fields, the results agree with perturbation theory.
Proton migration mechanism for the instability of organic field-effect transistors
Authors: Sharma A. , Mathijssen S. G. J. , Kemerink M. , de Leeuw D. M. , Bobbert P. A.
Published: December 2009

During prolonged application of a gate bias, organic field-effect transistors show an instability involving a gradual shift of the threshold voltage toward the applied gate bias voltage. We propose a model for this instability in p-type transistors with a silicon-dioxide gate dielectric, based on hole-assisted production of protons in the accumulation layer and their subsequent migration into the gate dielectric. This model explains the much debated role of water and several other hitherto unexplained aspects of the instability of these transistors.
Steady-state composition of a two-component gas bubble growing in a liquid solution: Self-similar approach
Authors: Gor G. Yu. , Kuchma A. E.
Published: December 2009

The paper presents an analytical description of the growth of a two-component bubble in a binary liquid-gas solution. We obtain asymptotic self-similar time dependence of the bubble radius and analytical expressions for the nonsteady profiles of dissolved gases around the bubble. We show that the necessary condition for the self-similar regime of bubble growth is the constant, steady-state composition of the bubble. The equation for the steady-state composition is obtained. We reveal the dependence of the steady-state composition on the solubility laws of the bubble components. Besides, the universal, independent from the solubility laws, expressions for the steady-state composition are obtained for the case of strong supersaturations, which are typical for the homogeneous nucleation of a bubble.
Physical and biological changes to a lengthening stream gradient following a decade of rapid glacial recession
Authors: FINN DEBRA S. , RÄSÄNEN KATJA , ROBINSON CHRISTOPHER T.
Published: December 2009

In mountains, environmental gradients are steep in both terrestrial and aquatic systems, and climate change is causing upward shifts of physical and biological features of these gradients. Glacial streams are an interesting system to evaluate such shifts both because streams have a linear nature (for simplicity of analysis), and because the stream habitat will at least temporarily lengthen as it follows receding glaciers upward. The Tschierva Glacier, Swiss Alps, receded 482 m upstream from 1997 to 2008. We tested the null hypothesis that the physical and biological stream gradient below this glacier maintained the same structure between these time periods, but simply shifted upward following the glacial source. We compared longitudinal patterns of water temperature and zoobenthic community structure in 1997 and 2007–2008 during three seasons (spring, summer, fall) along the uppermost ca. 5 stream km. Upward shifts were evident, including colonization of the newly exposed stream reaches by cold‐adapted taxa, and the appearance in 2007/2008 of four lower‐altitude species that were previously absent. Overall, however, results rejected the null hypothesis, instead revealing significant changes in gradient structures. These included a more steeply increasing temperature profile downstream of the glacier and increased amplitude of seasonal community turnover in 2007/2008 vs. 1997. Long‐term (1955–2007) flow records revealed increasing short‐term and seasonal hydrologic variability, which might have influenced the increased intra‐annual community variability. The steepening of the temperature gradient was likely caused by a warming lake‐outlet tributary upon which glacial influence was diminished between 1997 and 2007/2008. These results suggest that upward‐shifting gradients in glacial streams can involve complex interactions with other landscape elements and that local‐scale climate response can progress even more rapidly than the rate of glacial recession.
Low‐dose metronomic chemotherapy with cisplatin: can it suppress angiogenesis in H22 hepatocarcinoma cells?
Authors: Shen Fang‐Zhen , Wang Jing , Liang Jun , Mu Kun , Hou Ji‐Yuan , Wang Yan‐Tao
Published: December 2009

Low‐dose chemotherapy drugs can suppress tumours by restraining tumour vessel growth and preventing the repair of damaged vascular endothelial cells. Cisplatin is a broad‐spectrum, cell cycle‐non‐specific drug, but has serious side effects if used at high doses. There have been few reports on the anti‐angiogenic effects of low‐dose cisplatin and hence the effect of low‐dose metronomic (LDM) chemotherapy on the proliferation and neovascularization of H22 hepatocarcinoma cells is discussed in this research. The influence of LDM chemotherapy with cisplatin on human umbilical vascular endothelial cells (HUVECs) and proliferation of the HepG2 human hepatocarcinoma cell line were measured using MTT assays. The LDM group was treated with cisplatin 0.6 mg/kg/day; the control group with saline 0.2 ml; the maximum tolerated dose (MTD) group with cisplatin 9 mg/kg/day. Vascular endothelial growth factor (VEGF) and matrix metallopeptidase 2 (MMP‐2) were detected using immunohistochemical staining. A chicken chorio‐allantoic membrane (CAM) model was used to check the inhibitory effect of LDM chemotherapy with cisplatin on neovascularization in vivo. Low‐dose cisplatin inhibited HUVEC proliferation in a dose‐ and time‐dependent manner, but was ineffective in inhibiting HepG2 cell proliferation. Tumour growth was delayed in mice receiving LDM cisplatin, without apparent body weight loss, compared with mice that received MTD cisplatin. Microvessel density and expression of VEGF and MMP‐2 were much lower in mice receiving LDM cisplatin than in the control and MTD groups. Continuous low‐dose cisplatin suppressed CAM angiogenesis in vivo. LDM chemotherapy with cisplatin can inhibit the growth of blood vessel endothelial cells in vitro and shows anti‐angiogenic ability in vivo.
A quantitative study of lung dysfunction following haemorrhagic shock in rats
Authors: Sato Hiroaki , Tanaka Toshiko , Kita Toshiro , Tanaka Noriyuki
Published: December 2009

Haemorrhagic shock occasionally causes an episode of lung dysfunction, the severity of which appears to correlate with fatal outcome. Our previous study indicated that proinflammatory cytokines, such as tumour necrosis factor (TNF)‐α and interleukin (IL)‐1β, played a key role in the development of lung dysfunction through recruitment of activated neutrophils by causing pulmonary endothelial cell damage. Here, we examined this issue quantitatively by grading four groups of severity of bleeding in rats. As the amount of bleeding increased, the expression of mRNA for TNF‐α and IL‐1β in the lung tissue and the pulmonary serum levels of both cytokines increased progressively up to 5 h, and the frequency of activated neutrophils increased likewise. The lung dysfunction indices serum lactic dehydrogenase‐3 isozyme (LDH‐3), partial pressure of arterial oxygen (PaO2) and alveolar‐arterial oxygen tension difference (AaDO2) in blood deteriorated as the amount of bleeding increased. The frequency of activated neutrophils in the lung correlated well with the LDH‐3 level 5 h after haemorrhagic shock. The present results demonstrate that the increase of proinflammatory cytokines and the recruitment of activated neutrophils into the lung following haemorrhagic shock are quantitatively related to progression of lung dysfunction as the amount of bleeding increases.
Potential role of CXCL10 in the induction of cell injury and mitochondrial dysfunction
Authors: Singh Lipi , Arora Sunil Kumar , Bakshi Dapinder K. , Majumdar Siddarth , Wig Jai Dev
Published: December 2009

Chemokines have been known to play a critical role in pathogenesis of chronic pancreatitis and acinar cell death. However, the role played by one of the CXC chemokines: CXCL10 in regulation of acinar cell death has remained unexplored. Hence, this study was designed to assess the role of CXCL10 promoting apoptosis in ex vivo cultured acinar cells. Primary human pancreatic acinar cell cultures were established and exposed to varying doses of CXCL10 for different time intervals. Apoptotic induction was evaluated by both qualitative as well as quantitative analyses. Various mediators of apoptosis were also studied by Western blotting, membrane potential (Ψm) and ATP depletion in acinar cells. Analysis of apoptosis via DNA ladder and cell death detection – ELISA demonstrated that CXCL10 induced 3.9‐fold apoptosis when administrated at an optimal dose of 0.1 μg of recombinant CXCL10 for 8 h. Quantitative analysis using FACS and dual staining by PI‐annexin showed increased apoptosis (48.98 and 53.78% respectively). The involvement of upstream apoptotic regulators like pJNK, p38 and Bax was established on the basis of their increased expression of CXCL10. The change of Ψm by 50% was observed in the presence of CXCL10 in treated acinar cells along with enhanced expression of Cytochrome C, apaf‐1 and caspase 9/3 activation. In addition, ATP depletion was also noticed in CXCL10 stimulated acinar cells. CXCL10 induces cell death in human cultured pancreatic cells leading to apoptosis and DNA fragmentation via CXCR3 signalling. These signalling mechanisms may play an important role in parenchymal cell loss and injury in pancreatitis.
Relative importance of habitat connectivity in shaping the genetic profiles of two southern African elephant‐shrews
Authors: Smit Hanneline A. , Watson Johan , Jansen van Vuuren Bettine
Published: December 2009

Aim  When interpreting genetic patterns across a landscape it is surprisingly difficult to disentangle the effects of landscape connectivity from those of species biology. Here, the spatial distributions of genetic variation of two sympatric elephant‐shrew species, the western rock elephant‐shrew (Elephantulus rupestris) and the round‐eared elephant‐shrew (Macroscelides proboscideus), are determined and compared. We selected these species because they have similar biologies but differ markedly in habitat use, the rationale being that differences in their genetic structure should be a result largely of landscape variables directly or indirectly affecting dispersal rather than of the biology of the species.

Location  South Africa and Namibia.

Methods  Mitochondrial sequence data (control region and cytochrome b) were used to describe the phylogeographic structure of these elephant‐shrew species across their distribution. To determine whether genetic variation is significantly structured, spatial analyses of molecular variation were performed. Isolation‐by‐distance versus alternative patterns of genetic structure was investigated using a Mantel test.

Results  Our analyses indicated an overall structured genetic profile for E. rupestris, a species closely associated with rocky outcrops. This was in contrast to a pattern mostly of isolation‐by‐distance across the distribution of M. proboscideus, a species found on gravel plains.

Main conclusions  Specific landscape features will differentially affect gene flow (both historical and current), and therefore also the spatial genetic structure, of species with markedly different habitat requirements. The genetic profiles for the two species included here support predictions based on the connectivity of their respective occupied habitats. The results also support the more general prediction that species with a naturally clustered distribution (such as E. rupestris) should have a more structured genetic pattern than those having a more continuous distribution (M. proboscideus).
DCTN1 mutations are implicated in multiple neurodegenerative disorders
Authors: Uribe V
Published: December 2009

DCTN1 mutations in Perry syndrome

Farrer et al. (2009)

Nature Genetics 40: 163–165
Sovereign Wealth Funds: Stylized Facts about their Determinants and Governance*
Authors: Aizenman Joshua , Glick Reuven
Published: December 2009

Concerns about the implications of foreign investments by sovereign wealth funds (SWFs) stem in large part from apprehensions about the objectives and governance quality of these institutions. This paper contributes to a better understanding of the stylized facts of SWFs by providing a statistical analysis of a range of characteristics of SWFs, including the motivation for their establishment as well as their size, governance and effect on reserve management behaviour. Specifically, it estimates what factors foster the establishment of SWFs as well as affect their size. It also investigates the extent to which the governance and transparency of individual SWFs correlate with domestic and global governance practices. Lastly, it analyses how asset accumulation by SWFs may affect central bank holdings of official reserves.
Erasure: Temporality and the Second Generation
Authors: FELLOWS DIANE
Published: December 2009

This essay is about one street, Lottumstraße, in Berlin, Germany, where my parent and grandparents lived prior to 1940. The current morphology of the street is contrasted with my mother's experience of life on Lottumstraße during the 1930s. The essay is part of a longer investigation regarding issues of post‐memory as interpreted by the second and third generation of trauma survivors. The essay suggests that, through the act of erasure, traces of the original urban or street condition, and the subsequent urban mark‐making of each successive generation, would be perceived and interpreted in order to authenticate the particulars of place over time. Traces underscore the responsibility to not only remember historic events but to recognize that those events have contemporary political and social implications. The larger scope of the work includes a film production titled ‘TopoNarratives 1‐4’: four short stories based upon specific people and places shaped by the events of the second world war that resonate through subsequent generations across topographies and contemporary political events. The work investigates the relationship of the second generation's personal construction of place to the public consequence of those private interpretations within the built environment.

L'essai concerne une rue de Berlin, Lottumstraße, où ma mère et mes grands‐parents ont vécu avant 1940. Il met en opposition la morphologie actuelle de la rue et l'expérience de vie de ma mère pendant les années 1930. Ce travail s'inscrit dans une étude plus longue sur des aspects de la post‐mémoire dans son interprétation par les deuxième et troisième générations de survivants à des traumatismes. Par l'acte d'effacement, les traces de l'état originel de la ville ou de la rue, ainsi que les empreintes urbaines ultérieures de chaque génération, sont perçues et interprétées de manière à authentifier les caractéristiques d'un lieu à travers le temps. Ces traces soulignent la responsabilité de ne pas oublier des événements historiques, mais aussi celle de reconnaître les implications politiques et sociales contemporaines de ceux‐ci. Le champ élargi de l'étude comprend la production d'un film intitulé‘TopoNaratives 1‐4’, soit quatre histoires courtes liées à des personnes et des lieux particuliers, façonnés par les épisodes de la seconde guerre mondiale qui résonnent au fil des générations successives à travers les topographies et les événements politiques contemporains. Le travail examine le lien entre l'élaboration individuelle d'un lieu par la deuxième génération et l'impact public de ces interprétations privées au sein de l'environnement construit.
Packing identical spheres into a cylinder
Authors: Stoyan Yu. G. , Yaskov G. N.
Published: December 2009

The paper deals with the optimization problem of packing identical spheres into a cylinder of minimal height. A mathematical model of the problem is constructed and its characteristics are considered. On the ground of characteristics, a strategy of searching for an approximation to a global minimum is offered. The strategy includes a special search tree construction, a modification of the Zoutendijk method of feasible directions to calculate local minima, and a modification of the decremental neighborhood method to search for an approximation to a global minimum. Numerical examples and performance analysis of solutions are given. On the basis of the mathematical model and numerical experiment, a number of conclusions are drawn.
Infantile spasms and pigmentary mosaicism
Authors: Hansen Lars K. , Bygum Anette , Krogh Lotte N.
Published: December 2009

We present a 3‐year‐old boy with pigmentary mosaicism and persistent intractable infantile spasms due to mosaicism of chromosome 7. Getting the diagnosis of pigmentary mosaicism in a child with infantile spasms may not be easy, as most diagnostic work‐up is done in infancy, at a time when skin manifestations can be subtle. We stress the need for a meticulous search for an etiology in cases of infantile spasms. Diagnostic work‐up should include a dermatologic evaluation with skin biopsies for fibroblast culture (and karyotyping) from abnormal pigmented skin areas.
Role of Proton Magnetic Resonance Spectroscopy in Differentiating Oligodendrogliomas from Astrocytomas
Authors: Chawla Sanjeev , Oleaga Laura , Wang Sumei , Krejza Jaroslaw , Wolf Ronald L. , Woo John H. , O'Rourke Donald M. , Judy Kevin D. , Grady Michael S. , Melhem Elias R. , Poptani Harish
Published: December 2009

BACKGROUND AND PURPOSE

Preoperative differentiation of astrocytomas from oligodendrogliomas is clinically important, as oligodendrogliomas are more sensitive to chemotherapy. The purpose of this study was to assess the role of proton magnetic resonance spectroscopy in distinguishing astrocytomas from oligodendrogliomas.

METHODS

Forty‐six patients [astrocytomas (n= 17) and oligodendrogliomas (n= 29)] underwent magnetic resonance imaging and multi voxel proton magnetic resonance spectroscopic imaging before treatment. Peak areas for N‐acetylaspartate (NAA), creatine (Cr), choline (Cho), myo‐inositol (mI), glutamate/glutamine (Glx), and lipids + lactate (Lip+Lac) were analyzed from voxels that exhibited hyperintensity on fluid‐attenuated inversion recovery images and were normalized to Cr from each voxel. The average metabolite/Cr ratios from these voxels were then compared between astrocytomas and oligodendrogliomas. Receiver‐operating curve analyses were used as measures of differentiation accuracy of metabolite ratios. A threshold value for a metabolite ratio was estimated by maximizing the sum of sensitivity and specificity.

RESULTS

A significant difference in mI/Cr was observed between astrocytomas and oligodendrogliomas (.50 ± .18 vs. 0.66 ± 0.20, P < .05). Using a threshold value of .56 for mI/Cr ratio, it was possible to differentiate oligodendrogliomas from astrocytomas with a sensitivity of 72.4% and specificity of 76.4%.

CONCLUSION

These results suggest that mI/Cr might aid in distinguishing oligodendrogliomas from astrocytomas.

J Neuroimaging 2010;20:3‐8.
Elevated Levels of Pre‐Procedural High‐Sensitivity C‐Reactive Protein Is Associated with Midterm Restenosis after Extra‐ and Intracranial Stenting
Authors: Gupta Rishi , Bhatt Archit , Kassab Mounzer , Majid Arshad
Published: December 2009

BACKGROUND AND PURPOSE

High‐sensitivity C‐reactive protein (hsCRP) is an inflammatory marker associated with subsequent coronary events and neointimal hyperplasia after coronary artery stent placement. We sought to determine if elevated levels of hsCRP are associated with restenosis after placement of extra‐ and intracranial stents.

METHODS

We retrospectively reviewed 73 consecutive patients at Michigan State University from July 2006 until June 2007 who underwent treatment with carotid artery stent placement or intracranial stent placement. Data were collected in regards to demographics, pre‐procedural hsCRP, and LDL levels, and angiographic variables characterizing the lesion before and after treatment. A binary logistic regression model was constructed to determine independent predictors of restenosis.

RESULTS

A total of 73 patients with a mean age of 69 ± 11 years were studied. A total of 57 patients were treated with extracranial carotid stenting, 22 (38%) of whom were symptomatic, while 16 patients underwent intracranial stenting (all were symptomatic). There were 9 patients (4 intracranial stents [25%] and 5 carotid stents [8.8%]) who developed a restenosis of >50%. In binary logistic regression modeling, the following variables were found to be independently predictive of developing restenosis: smaller vessel diameter (OR .49, 95% CI .23‐.98, P‐value .046) and elevated hsCRP (OR 2.2, 95% CI 1.29‐6.66, P‐value .018).

CONCLUSIONS

Elevated levels of pre‐procedural hsCRP may be predictive of the development of neointimal hyperplasia in patients treated with extra‐ or intracranial stenting procedures. Future prospective multicenter studies will be required to confirm these findings.

J Neuroimaging 2010;20:74‐77.
Measurement of Antiplatelet Inhibition during Neurointerventional Procedures: The Effect of Antithrombotic Duration and Loading Dose
Authors: Pandya DJ , Fitzsimmons BFM , Wolfe TJ , Hussain SI , Lynch JR , Ortega‐Gutierrez S , Zaidat OO
Published: December 2009

BACKGROUND/OBJECTIVE

Symptomatic thromboembolic events are the most common complications associated with aneurysm coiling, and carotid and intracranial stenting. Our objective is to assess the effect of aspirin (ASA) and clopidogrel dose and duration on platelet inhibition using a point of care assay in neurointerventional (NI) suite.

METHOD

The dose, duration, and point of care platelet function assay data for clopidogrel and aspirin therapy were prospectively collected between February 2006 and November 2007. Inadequate platelet inhibition for ASA was defined as ≥550 ASA reaction units (ARU), and for clopidogrel was defined as ≤50% inhibition of the P2Y12/ADP receptor

RESULTS

We collected data from 216 consecutive patients. Inadequate platelet inhibition was noted in 13% of patients on aspirin and 66% of patients on clopidogrel (P‐value < .0001). Patients taking clopidogrel 75 mg for ≥7 days, 300 mg for 24 hours, and 600 mg same day load had a mean P2Y12/ADP inhibition of 45%, 35% (P‐value = .09), and 16%, respectively (P‐value = .005).

CONCLUSION

Premedication with clopidogrel, in contrast to aspirin, does not achieve adequate platelet inhibition in about two‐third of the patients. Same day antiplatelet loading may be insufficient to achieve adequate platelet inhibition and should be avoided if clinically feasible.

J Neuroimaging 2010;20:64‐69.
Decreased Cortical Somatosensory Finger Representation in X‐Linked Recessive Bulbospinal Neuronopathy (Kennedy Disease): A Magnetoencephalographic Study
Authors: Suntrup Sonja , Kristina Teismann Inga , Steinstraeter Olaf , Bernd Ringelstein Erich , Pantev Christo , Dziewas Rainer
Published: December 2009

BACKGROUND

Kennedy disease (KD) clinically presents as progressive lower motor neuron disease with minimal or no sensory impairment. However, electrophysiological studies found abnormal somatosensory‐evoked potentials even in absence of clinical deficits. Little is known about possible influences of this sensory neuropathy on the central somatosensory processing.

METHODS

In this study, the cortical topography of index finger representation was studied in 7 patients with genetically proven KD compared to healthy control subjects by means of magnetoencephalography using an established stimulation paradigm. Data analysis was carried out with synthetic aperture magnetometry (SAM). Additionally, the latency and source amplitude of the earliest cortical somatosensory‐evoked field (SEF) component were determined based on traditional single dipole source analysis.

RESULTS

In KD patients the latency of the SEF was prolonged (48.6 vs. 37.4 ms, P < .005). There was no significant difference in dipole source amplitude, but stimulus‐related SAM activation of the contralateral sensorimotor cortex (pseudo‐t‐values –.107 vs. –.199, P < .05), including maximum activity (53.5%), was reduced.

CONCLUSIONS

These results implicate that even subclinical sensory neuropathy leads to possible functional reorganization of the sensorimotor cortex in KD patients and reinforces the view that in KD the somatosensory system is extensively involved.
Stenotrophomonas maltophilia: a very rare cause of tropical pyomyositis
Authors: THOMAS Joe , PRABHU Vadivelmurugan Nagasubramani Naga , VARAPRASAD Irlapatti Rajendra , AGRAWAL Sumeet , NARSIMULU Gumdal
Published: December 2009

Pyomyositis is a purulent infection of skeletal muscles that arise from hematogenous spread associated with abscess formation. Most often caused by Staphylococcus aureus in more than 90–95% of cases but other rare organisms can cause this infection. Herein we report a rare case of strenotrophomonas maltophilia as a cause of pyomyositis which is a rare occurrence, especially in immunocompetent adults. Strenotrophomonas is a multidrug‐resistant aerobic non‐fermentative, non‐sporulating, Gram‐negative bacillus which usually produces nosocomial infections, but community‐acquired infections are also rarely reported. This a first case report of strenotrophomonas maltophilia causing pyomyositis in an immunocompetent adult.
LNA‐substituted degenerate primers improve detection of nitrogenase gene transcription in environmental samples
Authors: Burbano Claudia Sofía , Reinhold‐Hurek Barbara , Hurek Thomas
Published: December 2009

In order to study the active diazotrophic bacterial community and to capture the majority of its individuals in environmental samples, strategies improving gene detection by increasing sensitivity and efficiency of PCR reactions are highly desirable. Since LNA (locked nucleic acids) modifications might alleviate a low sensitivity and specificity often limiting PCR reactions utilizing degenerate primers, the effect of LNA substituted primers on the detection of nifH transcripts in roots of rice and sugar cane by direct reverse transcription polymerase chain reaction (RT‐PCR) was studied. The LNA substitution of the RT primer increased the sensitivity of the RT‐PCR up to 26‐fold, whereas LNA substitution of the PCR primers decreased specificity. Terminal restriction fragment length polymorphism (T‐RFLP) analysis of RT‐PCR products showed that LNA substitutions in the RT‐primer did not change the pattern of nifH cDNA phylotypes. The use of the LNA‐substituted RT‐primer allowed the detection of nifH transcripts in sugar cane, where DNA primers alone failed to produce RT‐PCR products. These results suggest that similar improvements to PCR detection of nucleic acids can be expected for other environmental samples and genes likewise, when LNA‐substituted primers are used.
Molecular evaluation of the human gut methanogenic archaeal microbiota reveals an age‐associated increase of the diversity
Authors: Mihajlovski Agnès , Doré Joël , Levenez Florence , Alric Monique , Brugère Jean‐François
Published: December 2009

The methanogenic diversity of the human intestinal microbiota has long been viewed as composed of two Methanobacteriales: Methanobrevibacter smithii and Methanosphaera stadtmanae. Recently, Mx‐01, a new phylotype hypothesized to belong to a putative sixth methanogenic order, was recovered from human faeces. Here we examined the diversity and the distribution of methanogens among healthy people of three age groups by analysing mcrA and 16S rDNA clones. The mcrA analysis of ∼1200 clones revealed that the usual Methanobacteriales were present without any significant difference among adults and elderly (respectively 60% and 80% of carriers, n = 40, P = 0.3). In addition, four new phylotypes that grouped with Mx‐01 in the same monophyletic clade were recovered. These phylotypes were significantly more frequently detected in elderly people (40%, n = 20) than in adults (10%, n = 20, P = 0.065). In parallel, new 16S rDNA phylotypes affiliated near or within Thermoplasmatales were recovered. Altogether, these results indicate an age‐related apparition of Mx‐phylotypes, putatively methanogenic, which are formed of several species carrying a mcrA gene and that are not related to any of the five methanogenic orders. These species may be related to Thermoplasmatales or may cohabit with archaeal species related to Thermoplasmatales.
Joint Pricing and Contingent Free‐Shipping Decisions in B2C Transactions
Authors: Leng Mingming , Becerril‐Arreola Rafael
Published: December 2009

We consider an online retailer's joint pricing and contingent free‐shipping (CFS) decisions in both monopoly and duopoly structures, which is an important marketing‐operations interface problem. We begin by investigating the impacts of a retailer's decisions on consumers' purchase behaviors, and show that the CFS strategy is useful to acquire the consumers with large order sizes. Then, we compute the probability of repeated purchases, and construct an expected profit function for an online retailer in the monopolistic setting. We find that the fixed shipping fees may have the largest impact on the retailer's profit among all shipping‐related parameters, and the retailer can benefit more from homogeneous markets than from heterogeneous ones. Next, we consider the competition between two retailers in the duopoly structure, and analytically show that, if two retailers have identical fixed and variable shipping fees, then their equilibrium decisions are equal. In order to numerically find a Nash equilibrium for two retailers, we develop a simulation approach using Arena and OptQuest. Our simulation‐based examples suggest that, as a result of the competition, the two retailers should decrease their profit margins but increase their CFS cutoff levels if they have the same fixed and also the same variable shipping fees.
The Impact of External Demand Information on Parallel Supply Chains with Interacting Demand
Authors: Zhang Xiaolong , Zhao Yao
Published: December 2009

This paper considers two parallel supply chains with interacting demand streams. Each supply chain consists of one supplier and one retailer. The two demand streams are jointly described with a vector autoregressive time‐series process in which they interact and their respective innovation errors correlate contemporaneously. For each supply chain, we develop insights into when and how much the supplier and the retailer can improve on their forecasting accuracy if the external demand history of the other supply chain is utilized. When this external demand history is not available or made available after a time lag, we develop a partial process and a delayed process to characterize the demand structure that the retailer can recover from the available demand histories. Our results show that the external demand history of the other supply chain always helps the retailer make better forecasts when demand streams interact; however, the enhanced information alters the retailer's order process, which may produce larger forecasting errors for the supplier. Conditions are established for the supplier to benefit from the external demand history of the other supply chain.
The Impact of Organizational Structure on Mass Customization Capability: A Contingency View
Authors: Huang Xiaowen , Kristal Mehmet Murat , Schroeder Roger G.
Published: December 2009

This study investigates the role of organizational structure in facilitating the development of mass customization (MC) capability in various manufacturing settings. Specifically, three dimensions of organizational structure are considered—flatness, centralization, and employee multifunctionality. We model organizational structure as a second‐order factor whose value is captured on a mechanistic‐organic continuum, where the organic form is characterized by a flat, decentralized structure with a wide use of multifunctional employees. We propose that a positive relationship exists between the organic organizational structure and MC capability. Additionally, building upon contingency theory, we argue that this positive relationship is moderated by mass customizer type—full mass customizers, which customize products at the design or fabrication stage of the production cycle, versus partial customizers, which customize products only at the assembly or delivery stages. Based on a study of 167 manufacturing plants from three industries and eight countries, we find that, for the overall sample, organic structure plays a significant role in enabling firms to pursue MC capability. However, an analysis of full versus partial mass customizers shows that the positive impact of organic structure on MC capability is statistically significant only for full mass customizers, not for partial mass customizers.
On the Nonsimilarity Boundary-Layer Flows of Second-Order Fluid Over a Stretching Sheet
Authors: You Xiangcheng , Xu Hang , Liao Shijun
Published: December 2009

In this paper, the nonsimilarity boundary-layer flows of second-order fluid over a flat sheet with arbitrary stretching velocity are studied. The boundary-layer equations describing the steady laminar flow of an incompressible viscoelastic fluid past a semi-infinite stretching flat sheet are transformed into a partial differential equation with variable coefficients. An analytic technique for highly nonlinear problems, namely, the homotopy analysis method, is applied to give convergent analytical approximations, which agree well with the numerical results given by the Keller box method. Furthermore, the effects of physical parameters on some important physical quantities, such as the local skin-friction coefficient and the boundary-layer thickness, are investigated in detail. Mathematically, this analytic approach is rather general in principle and can be applied to solve different types of nonlinear partial differential equations with variable coefficients in physics.
System Dynamics of the Open-Draw With Web Adhesion: Particle Approach
Authors: Edvardsson Sverker , Uesaka Tetsu
Published: December 2009

In the present work we propose a particle approach, which is designed to treat complex mechanics and dynamics of the open-draw sections that are still present in many of today’s paper machines. First, known steady-state continuous solutions are successfully reproduced. However, it is shown that since the boundary conditions depend on the solution itself, the solutions for web strain and web path in the open-draw section are generally time-dependent. With a certain set of system parameters, the nonsteady solutions are common. A temporal fluctuation of Young’s modulus, for example, destabilizes the system irreversibly, resulting in the continuous growth of web strain, i.e., break. Finally we exemplify with some strategic draw countermeasures how to prevent a dangerous evolution in the web strain.
Kinematic Analysis of a Swash-Plate Controlled Variable Displacement Axial-Piston Pump With a Conical Barrel Assembly
Authors: Shi Zhiru , Parker Gordon , Granstrom Jonathan
Published: December 2009

Variable displacement, swash-plate controlled, axial-piston pumps are widely used in applications that require high pressure and variable flow rates. The pump consists of a rotating barrel assembly that houses several pistons in a circular array. A swash-plate is used to control the displacement of the pistons to adjust the output flow of hydraulic fluid. As the barrel rotates, the pistons slide along the angled swash-plate and draw oil from the supply and then discharge oil into the high pressure circuit. This results in an almost constant output flow rate. This paper analyzes the kinematics of a pump based on its geometry dependent characteristics. The analysis assumes an idealized case in which there is no oil leakage and the fluid is considered to be incompressible. It is revealed through the analysis that the piston displacement and the pump output flow are slightly increased by using a conical barrel. Instantaneous and mean flow rate equations are used to describe the output flow characteristics and flow ripple effect. The output flow rate ripple profile is found to be a function of both swash-plate angle and the conical barrel angle. A term defined as the flow rate uniformity coefficient is used to better quantify the flow ripple phenomenon. A frequency analysis is performed on the output flow rate and an additional order is found to be present when using a conical barrel pump versus one with a cylindrical barrel when the pumps have an odd number of pistons. Conical barrel piston pumps are found to have a slight increase in piston displacement, velocity, and acceleration relative to the rotating barrel frame of reference over a pump with a cylindrical barrel. This translates into an increase in the output flow rate for a conical piston pump under the same operating conditions. The conical barrel is also found to have a reduction in the rotational inertia allowing for faster angular acceleration. The presence of an extra order from a frequency analysis for a conical pump with an odd number of pistons has the potential to cause unwanted noise or vibration to the structure or components attached to the pump.