bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystal structure of NusG N‐terminal (NGN) domain from Methanocaldococcus jannaschii and its interaction with rpoE″
Authors: Zhou Huihao , Liu Qi , Gao Yongxiang , Teng Maikun , Niu Liwen
Published: April 2009

Transcription in archaea employs a eukaryotic‐type transcription apparatus but uses bacterial‐type transcription factors. NusG is one of the few archaeal transcription factors whose orthologs are essential in both bacteria and eukaryotes. Archaeal NusG is composed of only an NusG N‐terminal (NGN) domain and a KOW domain, which is similar to bacterial NusG but not to the eukaryotic ortholog, Spt5. However, archaeal NusG was confirmed recently to form a complex with rpoE″ that was similar to the Spt5‐Spt4 complex. Thus, archaeal NusG presents hybrid features of Spt5 and bacterial NusG. Here we report the crystal structure of NGN from the archaea Methanocaldococcus jannaschii (MjNGN). MjNGN folds to an α‐β‐α sandwich without the appendant domain of bacterial NGNs, and forms a unique homodimer in crystal and solution. MjNGN alone was found to be sufficient for rpoE″ binding and an MjNGN‐rpoE″ model has been constructed by rigid docking. Proteins 2009. © 2009 Wiley‐Liss, Inc.
On the origin of the catalytic power of carboxypeptidase A and other metalloenzymes
Authors: Kilshtain Alexandra Vardi , Warshel Arieh
Published: April 2009

Zinc metalloenzymes play a major role in key biological processes and carboxypeptidase‐A (CPA) is a major prototype of such enzymes. The present work quantifies the energetics of the catalytic reaction of CPA and its mutants using the empirical valence bond (EVB) approach. The simulations allow us to quantify the origin of the catalytic power of this enzyme and to examine different mechanistic alternatives. The first step of the analysis used experimental information to determine the activation energy of each assumed mechanism of the reference reaction without the enzyme. The next step of the analysis involved EVB simulations of the reference reaction and then a calibration of the simulations by forcing them to reproduce the energetics of the reference reaction, in each assumed mechanism. The calibrated EVB was then used in systematic simulations of the catalytic reaction in the protein environment, without changing any parameter. The simulations reproduced the observed rate enhancement in two feasible general acid‐general base mechanisms (GAGB‐1 and GAGB‐2), although the calculations with the GAGB‐2 mechanism underestimated the catalytic effect in some treatments. We also reproduced the catalytic effect in the R127A mutant. The mutation calculations indicate that the GAGB‐2 mechanism is significantly less likely than the GAGB‐1 mechanism. It is also found, that the enzyme loses all its catalytic effect without the metal. This and earlier studies show that the catalytic effect of the metal is not some constant electrostatic effect, that can be assessed from gas phase studies, but a reflection of the dielectric effect of the specific environment. Proteins 2009. © 2009 Wiley‐Liss, Inc.
Hurricane formation in diabatic Ekman turbulence
Authors: Schecter David A. , Dunkerton Timothy J.
Published: April 2009

This article investigates the emergence of hurricanes from chaotic swirling motions in a three‐layer model of the tropical troposphere that includes basic parametrizations of cumulus convection and air‐‐sea interaction. The chaotic flow is referred to as diabatic Ekman turbulence (DET), in order to emphasize that cumulus convection and Ekman pumping are critical to its behaviour. The time required for hurricane formation in DET is examined over a broad range of sea‐surface temperatures, tropical latitudes and surface exchange coefficients for moist entropy and momentum. The mean trends are sensible, but for a given set of parameters, the genesis time can vary significantly with subtle changes to the initial turbulence. Moreover, hurricanes do not always form. In the event that a tropical depression develops into a hurricane, the process is highly asymmetric. Intensification involves a shear‐flow instability, the production of mesovortices and contraction of the basic circulation. Despite the complex evolution, the intensification rate is largely consistent with the expectations of a quasi‐linear stability analysis. Properties of mature hurricanes and the nature of their fluctuations are discussed in the context of the model. Copyright © 2009 Royal Meteorological Society
The impact of moist processes on the African easterly jet–African easterly wave system
Authors: Cornforth R. J. , Hoskins B. J. , Thorncroft C. D.
Published: April 2009

The African Easterly Jet–Easterly Wave (AEJ–AEW) system was explored in an idealised model. Prescribed zonally symmetric surface temperature and moisture profiles determine the AEJ which becomes established through meridional contrasts in dry and moist convection.

As in previous studies, a realistic AEJ developed with only dry convection. Including moist processes, increased its development rate, but reduced its speed and meridional extent. AEWs grew through barotropic–baroclinic conversions. Negative meridional potential vorticity (PV) gradients arose in the zonally symmetric state through the intrusion of the low‐PV Saharan boundary layer. Since moist processes strengthened this significantly through diabatically generated PV in the Intertropical Convergence Zone, moist AEWs were three times stronger. Larger barotropic conversions and faster AEJ development increased the moist wave growth‐rate. Jet‐level and northerly low‐level amplitudes grew, but in the moist case the low‐level amplitudes weakened as the AEW interacted with convection, consistent with their absence from observations during the peak monsoon. Striking dependencies between the AEJ, AEW and rainfall existed. Two time‐scales governed their evolution, depending on the transfer coefficients: (1) the AEJ's replenishment rate influenced by heat fluxes, and (2) the wave growth‐rate, by damping, and the slower jet development rate.

Moist AEWs were characterized by intermittent growth/decay, with growth preceded by increased mean rainfall and later, weakening AEJs. These dependencies established an internal 8–10‐day variability, consistent with intra‐seasonal observations of 9‐day rainy sequences. This internal variability offers an alternative explanation to the previously proposed external forcing and a new view of the moist AEW life cycle. Copyright © 2009 Royal Meteorological Society
Measurements of aerosol properties from aircraft, satellite and ground‐based remote sensing: a case‐study from the Dust and Biomass‐burning Experiment (DABEX)
Authors: Johnson B. T. , Christopher S. , Haywood J. M. , Osborne S. R. , McFarlane S. , Hsu C. , Salustro C. , Kahn R.
Published: April 2009

This paper presents aircraft measurements of aerosol optical properties and radiative effects from the Dust and Biomass‐burning Experiment (DABEX) over West Africa. On 19 January 2006 cloud‐free skies and high aerosol loading provided ideal conditions for an intercomparison of aircraft, satellite and ground‐based remote sensing instruments. Aerosol size distributions, optical properties, aerosol optical depth (AOD) and downwelling solar radiation were measured by the UK FAAM aircraft in the region of Niamey, Niger. The aircraft in situ measurements showed a mixture of dust and biomass‐burning aerosols and indicated an AOD of 0.79 (at 550 nm) that compared well against AODs from the Banizoumbou Aerosol Robotic Network (AERONET) site (0.74) and a Microtops sunphotometer (0.72). AERONET size distributions showed a good degree of similarity with the aircraft in situ measurements. AERONET single‐scattering albedos were also in fairly close agreement with the aircraft, having values of 0.85 and 0.87, respectively (at 550 nm). Measurements of downwelling solar radiation from the aircraft compared well with measurements from the Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) at Niamey. Radiative transfer modelling suggested a 130–160 W m−2 instantaneous reduction of downwelling solar radiation by the aerosol column (15–18% of the total flux). Measurements of downwelling solar radiation compared reasonably well against radiative transfer modelling based on the aircraft in situ data. Satellite retrievals of AOD from MISR and MODIS Deep Blue were within 0.05 of the ground‐based sunphotometers measurements although there were discrepancies in optical properties retrieved by MISR, as compared to AERONET and the aircraft. Copyright © Royal Meteorological Society, Crown Copyright 2009
Infrasound generation by tornadic supercell storms
Authors: Akhalkatsi M. , Gogoberidze G.
Published: April 2009

Acoustic wave generation by turbulence in a stratified, moist atmosphere is studied. It is shown that, in saturated moist air turbulence, in addition to the Lighthill's quadrupole and dipole sources of sound (related to stratification and temperature fluctuations), there exist monopole sources related to heat and mass production during the condensation of moisture. We determine the acoustic power of these monopole sources and show that this radiation is dominant for typical parameters of strong convective storms. The results are in good qualitative agreement with the main observed characteristics of infrasound radiation by strong convective storms, e.g. total acoustic power and characteristic frequency. Copyright © 2009 Royal Meteorological Society
Improving the numerical prediction of a cyclone in the Mediterranean by local potential vorticity modifications
Authors: Argence Sébastien , Lambert Dominique , Richard Evelyne , Pierre Chaboureau Jean , Philippe Arbogast Jean , Maynard Karine
Published: April 2009

This study explores the benefit that can be drawn from incorporating local potential vorticity (PV) modifications into a numerical forecast. The case under study is the severe cyclogenesis that occurred in the Western Mediterranean from 9 to 12 November 2001. This case was shown to be extremely sensitive to the upper‐level flow, which governed to a great extent the deepening of the depression and the location and intensity of its associated precipitation. Corrections of PV were guided by METEOSAT‐7 water vapour observations and restricted to the upper troposphere, mainly altering the topography of the dynamical tropopause. Using both the French operational global model ARPEGE and the non‐hydrostatic mesoscale model Meso‐NH, it is shown that carefully designed PV corrections lead to a substantial improvement in the simulation of the storm, both in terms of surface pressure, cloud cover and precipitation forecasts. Furthermore, the impact of the modifications is shown to be a maximum when they are introduced at the time corresponding to the incipient stage of cyclogenesis. Copyright © 2009 Royal Meteorological Society
Factors influencing cloud area at the capping inversion for shallow cumulus clouds
Authors: Lock A. P.
Published: April 2009

Large‐eddy simulations of marine cumulus clouds are performed. Aspects of the simulations are varied in order to identify those parameters that play a role in determining when the cumulus clouds spread out under the capping inversion into stratocumulus. These include the strength of the surface fluxes, which also affects the strength of the cumulus mass transport, the strength of the capping inversion, the moisture content of the free atmosphere, the strength of cloud‐top radiative cooling and whether there is significant precipitation or sedimentation of cloud drops. Tests are also performed to evaluate sensitivity to the model resolution.

As in previous studies, having sufficient resolution at the capping inversion is found to be important for robust simulation of any stratiform cloud that forms there. In addition, the cloud cover is found to be sensitive to many of the physical processes investigated. In the end, though, a clear and robust dependence emerges on the cloud‐top entrainment instability parameter, κ. For large κ, a typical (small) shallow cumulus cloud cover is seen. For κ below the threshold for buoyancy reversal, the cumulus spreads into a solid sheet of stratocumulus beneath the inversion. Consistent with previous studies, there is no abrupt transition and the cloud cover decreases smoothly as κ increases. The conclusion is reached that varying other parameters in the simulations affects the cloud cover through their impact on the size of the jumps across the inversion and thence κ. The implications for turbulent mixing parametrizations in general circulation models are discussed. © Crown Copyright 2009. Reproduced with the permission of HMSO. Published by John Wiley & Sons, Ltd.
Optimized port placement for in vivo biosensors
Authors: King Brady W. , Reisner Luke A. , Ellis R. Darin , Klein Michael D. , Auner Gregory W. , Pandya Abhilash K.
Published: April 2009

Background

We discuss the implementation of an automated port placement system for use with laparoscopic in vivo biosensors. Biosensors have physical limitations that make port placement crucial to proper data collection. The port placement process is prohibitively complex to execute optimally by human estimation.

Methods

Port placement algorithms were integrated into an image‐guided surgery system. Variables for optimization of ports include biosensor length, data collection restrictions, obstacles, and regions of interest. The port placement is applied to 3D virtual ‘patients’ created from medical imaging data. An example implementation for a Raman biosensor probe was created.

Results

The prototype system can correctly find ideal port locations on a virtual patient based on biosensor limitations and regions of interest. Conversely, the system can evaluate and score an individual port selected by a user.

Conclusion

As biosensors become incorporated into laparoscopic surgical environments, an automated port placement system would enable their optimized integration. Copyright © 2009 John Wiley & Sons, Ltd.
Involvement of the nucleolus in replication of human viruses
Authors: Greco Anna
Published: April 2009

Viruses are intracellular pathogens that have to usurp some of the cellular machineries to provide an optimal environment for their own replication. An increasing number of reports reveal that many viruses induce modifications of nuclear substructures including nucleoli, whether they replicate or not in the nucleus of infected cells. Indeed, during infection of cells with various types of human viruses, nucleoli undergo important morphological modifications. A large number of viral components traffic to and from the nucleolus where they interact with different cellular and/or viral factors, numerous host nucleolar proteins are redistributed in other cell compartments or are modified and some cellular proteins are delocalised in the nucleolus of infected cells. Well‐documented studies have established that several of these nucleolar modifications play a role in some steps of the viral cycle, and also in fundamental cellular pathways. The nucleolus itself is the place where several essential steps of the viral cycle take place. In other cases, viruses divert host nucleolar proteins from their known functions in order to exert new unexpected role(s). Copyright © 2009 John Wiley & Sons, Ltd.
Investigations on the leaf surface ultrastructure in grapevine (Vitis vinifera L.) by scanning microscopy
Authors: Bensalem‐fnayou A. , Jellouli N. , Bouamama B. , Mliki A. , Ghorbel A.
Published: April 2009

Several Scanning microscopy techniques were used to investigate the leaf surface ultrastructure in the local “Razegui” grapevine cultivar (Vitis vinifera L.). Conventional scanning electron microscopy performed on glutaraldehyde‐fixed samples allowed observation of well‐preserved epidermal cells with an overlaying waxy layer. At a high magnification, the waxy layer exhibited crystalline projections in the form of horizontal and vertical platelets. Also, to avoid eventual ultrastructural alterations inherent in the use of solvents during sample preparation, fresh leaf blade samples were directly observed by environmental scanning electron microscopy. A classical image of convex living epidermal cells was observed. At 2400× magnification, epicuticular waxes exhibited a granular structure. However, high‐magnification images were not obtained with this device. The atomic force microscopy (AFM) performed on fresh leaf blade samples allowed observation of a textured surface and heterogeneous profiles attributed to epicuticular wax deposits. AFM topography images confirmed further, the presence of irregular crystalloid wax projections as multishaped platelets on the adaxial surface of grapevine leaf. SCANNING 31: 127–131, 2009. © 2009 Wiley Periodicals, Inc.
Hierarchical additive modeling of nonlinear association with spatial correlations—An application to relate alcohol outlet density and neighborhood assault rates
Authors: Yu Qingzhao , Li Bin , Scribner Richard Allen
Published: April 2009

Previous studies have suggested a link between alcohol outlets and assaults. In this paper, we explore the effects of alcohol availability on assaults at the census tract level over time. In addition, we use a natural experiment to check whether a sudden loss of alcohol outlets is associated with deeper decreasing in assault violence. Several features of the data raise statistical challenges: (1) the association between covariates (for example, the alcohol outlet density of each census tract) and the assault rates may be complex and therefore cannot be described using a linear model without covariates transformation, (2) the covariates may be highly correlated with each other, (3) there are a number of observations that have missing inputs, and (4) there is spatial association in assault rates at the census tract level. We propose a hierarchical additive model, where the nonlinear correlations and the complex interaction effects are modeled using the multiple additive regression trees and the residual spatial association in the assault rates that cannot be explained in the model are smoothed using a conditional autoregressive (CAR) method. We develop a two‐stage algorithm that connects the nonparametric trees with CAR to look for important covariates associated with the assault rates, while taking into account the spatial association of assault rates in adjacent census tracts. The proposed method is applied to the Los Angeles assault data (1990–1999). To assess the efficiency of the method, the results are compared with those obtained from a hierarchical linear model. Copyright © 2009 John Wiley & Sons, Ltd.
Accurate estimates without local data?
Authors: Menzies Tim , Williams Steve , Elrawas Oussama , Baker Daniel , Boehm Barry , Hihn Jairus , Lum Karen , Madachy Ray
Published: April 2009

Models of software projects input project details and output predictions via their internal tunings. The output predictions, therefore, are affected by variance in the project details P and variance in the internal tunings T. Local data is often used to constrain the internal tunings (reducing T).

While constraining internal tunings with local data is always the preferred option, there exist some models for which constraining tuning is optional. We show empirically that, for the USC COCOMO family of models, the effects of P dominate the effects of T i.e. the output variance of these models can be controlled without using local data to constrain the tuning variance (in ten case studies, we show that the estimates generated by only constraining P are very similar to those produced by constraining T with historical data).

We conclude that, if possible, models should be designed such that the effects of the project options dominate the effects of the tuning options. Such models can be used for the purposes of decision making without elaborate, tedious, and time‐consuming data collection from the local domain. Copyright © 2009 John Wiley & Sons, Ltd.
Fetal intraperitoneal transfusion for iatrogenic twin anemia–polycythemia sequence after laser therapy
Authors: Herway C. , Johnson A. , Moise K. , Moise K. J.
Published: April 2009

Twin anemia–polycythemia sequence (TAPS) is a rare variant of twin–twin transfusion syndrome (TTTS) without the characteristic twin oligohydramnios–polyhydramnios sequence and cardiovascular milieu attributed to renin–angiotensin system mediators. It can occur spontaneously or iatrogenically after fetoscopic laser surgery. We report the case of a woman, gravida 2 para 1, with a monochorionic diamniotic pregnancy who developed Quintero Stage III TTTS. She underwent laser photocoagulation of identifiable anastomotic vessels and subsequently developed suspected TAPS 2 weeks later. The pregnancy was successfully treated with serial intrauterine intraperitoneal transfusions (IUT‐PTs) of red blood cells. Although TAPS is a rare condition, serial middle cerebral artery peak systolic velocity measurements are warranted as follow‐up in patients who have undergone fetoscopic laser surgery for TTTS. IUT‐PTs may be superior to intravascular intrauterine transfusions in the treatment of this condition. Copyright © 2009 ISUOG. Published by John Wiley & Sons, Ltd.
Fetal dilated cardiomyopathy caused by persistent junctional reciprocating tachycardia
Authors: Cornette J. , Ten Harkel A. D. J. , Steegers E. A. P
Published: April 2009

Ultrasound examination of a fetus at 32 weeks' gestation revealed dilated cardiomyopathy and a heart rate of 170 beats per minute. Prenatally, this mild tachycardia was not primarily suspected to be the cause of the myocardial changes. Postnatal electrocardiography revealed a persistent junctional reciprocating tachycardia (PJRT) and the diagnosis of tachycardia‐induced cardiomyopathy (TICM) became apparent. After conversion to a sinus rhythm under digoxin and amiodarone, the cardiac changes regressed. PJRT is a rare form of supraventricular tachycardia. The prenatal findings in the condition have previously been described retrospectively, but it can only be diagnosed postnatally by its characteristic electrocardiographic properties. This case indicates that TICM can occur at lower heart rates than previously assumed. Even severe prenatal cardiomyopathy may be reversible once sinus rhythm has been restored. Copyright © 2009 ISUOG. Published by John Wiley & Sons, Ltd.
Role of uterine artery Doppler in interpreting low PAPP‐A values in first‐trimester screening for Down syndrome in pregnancies at high risk of impaired placentation
Authors: Herraiz I. , López‐Jiménez E. A. , García‐Burguillo A. , Nieto O. , Villar O. P. , Escribano D. , Galindo A.
Published: April 2009

Objectives

Low maternal serum levels of pregnancy‐associated plasma protein‐A (PAPP‐A) are associated with both increased risk of aneuploidies and impaired trophoblastic invasion, while high uterine artery (UtA) resistance is associated with impaired trophoblastic invasion but not with an increased risk of aneuploidies. The aim of this study was to determine whether high UtA resistance plays a role in explaining low PAPP‐A levels in the absence of aneuploidies.

Methods

This was a prospective study of 116 singleton pregnancies at high risk for impaired placentation (having at least one major risk factor: prior history of pre‐eclampsia, pregestational diabetes mellitus, chronic hypertension, chronic kidney disease, body mass index >30, autoimmune disorder, thrombophilia or recurrent pregnancy loss), booked for routine assessment of risk for aneuploidies by means of the first‐trimester combined screening test (nuchal translucency thickness (NT) + PAPP‐A + beta‐human chorionic gonadotropin (β‐hCG)). Measurement of NT and the mean UtA pulsatility index (PI) were carried out at the 11 to 13 + 6‐week scan. All values were calculated in multiples of the median (MoM) adjusted for gestational age. A cut‐off risk of 1/270 at time of sampling was adopted to differentiate high‐ from low‐risk groups for trisomy 21.

Results

There were 108 patients deemed to be at low risk for trisomy 21 and eight at high risk. None had chromosomal defects, giving a false‐positive rate for trisomy 21 of 6.9%. The greatest differences between patients at low risk and those at high risk for trisomy 21 were found in their PAPP‐A (0.98 vs. 0.38 MoM, P < 0.01) and β‐hCG (1.09 vs. 1.77 MoM, P = 0.04) values. Greater NT thickness (1.02 vs. 0.90 MoM) and higher mean UtA‐PI (1.05 vs. 0.96 MoM) were recorded in the high‐risk group, although the differences did not reach statistical significance (P = 0.19 and 0.40, respectively). After log‐transformation there were no significant correlations between mean UtA‐PI and NT and between mean UtA‐PI and β‐hCG. There was a significant negative linear correlation between mean UtA‐PI and PAPP‐A (r = −0.331; P < 0.01). After adjusting the PAPP‐A values by UtA‐PI, the false‐positive rate for trisomy 21 decreased to 2.6%.

Conclusion

Mean UtA‐PI at the 11 to 13 + 6‐week scan may be an effect‐modifier variable for PAPP‐A that should be taken into account in the first‐trimester combined screening for aneuploidies, at least in pregnancies at high risk for impaired placentation. Copyright © 2009 ISUOG. Published by John Wiley & Sons, Ltd.
Can quantitative three‐dimensional power Doppler angiography be used to predict ovarian hyperstimulation syndrome?
Authors: Jayaprakasan K. , Jayaprakasan R. , Al‐Hasie H. A. , Clewes J. S. , Campbell B. K. , Johnson I. R. , Raine‐Fenning N. J.
Published: April 2009

Objective

To test the hypothesis that ovarian vascularity is increased in women developing ovarian hyperstimulation syndrome (OHSS) and to assess its value as a predictor of OHSS during in‐vitro fertilization (IVF).

Methods

118 subjects undergoing their first cycle of IVF had a three‐dimensional (3D) transvaginal ultrasound scan in the early follicular phase of the menstrual cycle preceding IVF treatment. 18 of them developed moderate or severe OHSS and 100 subjects had normal ovarian response. Antral follicle count, ovarian volume, and ovarian vascularity (vascularization index (VI), flow index (FI) and vascularization flow index (VFI)) were compared between OHSS and control groups. Multiple regression analysis was used to assess the predictive value of these variables against age, body mass index and basal follicle‐stimulating hormone level for the development of OHSS.

Results

The ovarian blood flow indices VI (11.1 ± 11.6 vs. 8.6 ± 7.3%; P = 0.23), FI (38.0 ± 4.8 vs. 38.0 ± 5.5; P = 0.95) and VFI (4.2 ± 3.3 vs. 3.5 ± 3.1; P = 0.40) were similar in the OHSS group and the normal responders. While antral follicle count was significantly higher in women developing OHSS (33.0 ± 15.1) than in the control group (19.2 ± 9.9, P < 0.001), ovarian volume did not differ between the two groups (10.6 ± 3.8 vs. 8.9 ± 4.8 cm3, respectively, P = 0.11). On multiple regression analysis, antral follicle count was the only significant predictor of OHSS (P < 0.01).

Conclusions

Women developing OHSS during IVF do not demonstrate an increased ovarian blood flow as measured by 3D ultrasound but do have a significantly higher antral follicle count, which is the only significant predictor of OHSS. Copyright © 2009 ISUOG. Published by John Wiley & Sons, Ltd.
Rigid PVC/(layered silicate) nanocomposites produced through a novel melt‐blending approach
Authors: Matuana Laurent M.
Published: April 2009

On the basis of the fusion behavior of poly(vinyl chloride) (PVC), the influence of compounding route on the properties of PVC/(layered silicate) nanocomposites was studied. Four different compounding addition sequences were examined during the melt compounding of PVC with montmorillonite (MMT) clay, including (a) a direct dry mixing of PVC and nanoclay, (b) an addition of nanoclay at compaction, (c) an addition of nanoclay at the onset of fusion, and (d) an addition of nanoclay at equilibrium torque. Both unmodified sodium montmorillonite (Na+‐MMT) and organically modified montmorillonite (Org.‐MMT) clays were used, and the effect of the addition sequence of the clay during compounding on its dispersion in the matrix was evaluated by X‐ray diffraction and transmission electron miscroscopy. The surface color change, dynamic mechanical analysis, and flexural and tensile properties of PVC/clay nanocomposites were also studied. The experimental results indicated that both the extent of property improvement and the dispersion of nanoparticles in PVC/(layered silicate) nanocomposites are strongly influenced by the degree of gelation achieved in PVC compounds during processing. The addition of nanoclay to PVC must be accomplished at the onset of fusion, when PVC particles are reduced in size, in order to produce nanocomposites with better nanodispersion and enhanced mechanical properties. Overall, rigid PVC nanocomposites with unmodified clay (Na+‐MMT) were more thermally stable and exhibited better mechanical properties than their counterparts with organically modified clay (Org.‐MMT). J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers
Policy‐based scanning with QoS support for seamless handovers in wireless networks
Authors: Yoo Sang‐Jo , Golmie Nada
Published: April 2009

Supporting seamless handovers between different wireless networks is a challenging issue. One of the most important aspects of a seamless handover is finding a target network and point of attachment (PoA). This is achieved by performing a so‐called channel scanning. In most handovers, such as between universal mobile telecommunications system (UMTS), wireless local area network (WLAN), and worldwide interoperability for microwave access (WiMAX), channel scanning causes severe service disruptions with the current PoA and degrades the quality of service (QoS) during the handover. In this paper, a new architecture for QoS supported scanning that can be generalized to different wireless networks is proposed. It employs two techniques. The first is for determining a policy‐based order for the channel scanning sequence. With this technique, depending on the network costs and user requirements, the policy engine determines the channel scanning order for different network types and sets up a scanning sequence of PoAs for a given network type. This policy‐based scanning order provides a faster discovery of the target PoA that meets the QoS demands of the user. The second technique consists of a QoS supported dynamic scanning algorithm where the scanning frequency and duration are determined based on the user QOS requirements. Most importantly, the scanning duration is scheduled to guarantee the user QoS requirements while the scan progresses. Simulation results show that the proposed mechanism achieves relatively short service disruptions and provides the desired quality to users during the scanning period. Copyright © 2009 John Wiley & Sons, Ltd.
Hybrid TOA/AOA estimation error test and non‐line of sight identification in wireless location
Authors: Wann Chin‐Der , Lin Han‐Yi
Published: April 2009

In this paper, a modified time‐of‐arrival (TOA) estimation error test and a hybrid time‐of‐arrival/angle‐of‐arrival (TOA/AOA) estimation error test for identification of line of sight (LOS) base stations (BSs) are proposed. The proposed schemes aim to improve the location accuracy of wireless location systems suffering from the non‐line of sight (NLOS) propagation errors. The modified TOA‐based estimation error test is considered a straightforward approach in identifying the LOS‐BS set when the number of LOS BSs is greater than or equal to three. When both TOA and AOA metrics are available, hybrid TOA/AOA squares of normalized estimation errors are formulated by adopting the approximate maximum likelihood (AML) estimation. The proposed hybrid estimation error test scheme is capable of identifying the LOS/NLOS status of each BS, and performing location estimation in the situation where only two LOS BSs exist. Simulation results show that the proposed schemes are capable of correctly identifying the LOS BSs and improving the overall location accuracy. Copyright © 2009 John Wiley & Sons, Ltd.
Drug‐eluting stent coatings
Authors: Puskas Judit E. , Muñoz‐Robledo Lyn G. , Hoerr Robert A. , Foley John , Schmidt Steven P. , Evancho‐Chapman Michelle , Dong Jinping , Frethem Chris , Haugstad Greg
Published: April 2009

This paper reviews the development of coronary stents from a polymer scientist's view point, and presents the first results of an interdisciplinary team assembled for the development of new stent systems. Poly(styrene‐b‐isobutylene‐b‐styrene) block copolymer (SIBS), a nanostructured thermoplastic elastomer, is used in clinical practice as the drug‐eluting polymeric coating on the Taxus coronary stent (trademark of Boston Scientific Co.). Our group has been developing new architectures comprising of arborescent (dendritic) polyisobutylene cores (D_SIBS), which were shown to be as biocompatible as SIBS. ElectroNanospray (Nanocopoeia Inc.™) was used to coat test coupons and coronary stents with selected DSIBS polymers loaded with dexamethasone, a model drug. The surface topology varied from smooth to nanosized particulate coating. This paper will demonstrate how drug release profiles were influenced by both the molecular weight of the polyisobutylene core and spraying conditions of the polymer‐drug mixture. Copyright © 2009 John Wiley & Sons, Inc.

This article is categorized under:

Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials
The Hsp90/Cdc37p chaperone system is a determinant of molybdate resistance in Saccharomyces cerevisiae
Authors: Millson Stefan H. , Nuttall James M. , Mollapour Mehdi , Piper Peter W.
Published: April 2009

Saccharomyces cerevisiae lacks enzymes that contain the molybdopterin co‐factor and therefore any requirement for molybdenum as a trace mineral supplement. Instead, high molybdate levels are inhibitory to its growth. Low cellular levels of heat shock protein 90 (Hsp90), an essential chaperone, were found to enhance this sensitivity to molybdate. Certain Hsp90 point mutations and co‐chaperone protein defects that partially compromise the function of the Hsp90/Cdc37p chaperone system also rendered S. cerevisiae hypersensitive to high molybdate levels. Sensitivity was especially apparent with mutations close to the Hsp90 nucleotide binding site, with the loss of the non‐essential co‐chaperone Sti1p (the equivalent of mammalian Hop), and with the abolition of residue Ser14 phosphorylation on the essential co‐chaperone Cdc37p. While it remains to be proved that these effects reflect direct inhibition of the Hsp90 of the cell by the MoO42+ oxyanion in vivo; this possibility is suggested by molybdate sensitivity arising with a mutation in the Hsp90 nucleotide binding site that does not generate stress sensitivity or an impaired stress response. Molybdate sensitivity may therefore be a useful phenotype to score when studying mutations in this chaperone system. Copyright © 2009 John Wiley & Sons, Ltd.
$^{2}_{\infty}\rm [Tb(Tz\ast)_{3}]$, A Homoleptic 2‐Dimensional Framework from a Solvent Free Synthesis of Terbium Metal with 1H‐1,2,3‐Triazole
Authors: Rybak Jens‐Christoph , Müller‐Buschbaum Klaus
Published: April 2009

Single crystalline $^{2}_{\infty}\rm [Tb(Tz\ast)_{3}]$, (Tz*)– = 1,2,3‐triazolate anion, C2H2N3–, was obtained by the reaction of terbium metal with the amine 1H‐1,2,3‐triazole. As no additional solvent was used, the formation of a homoleptic framework without additional co‐ligands is accessible. Furthermore molecular hydrogen is produced. $^{2}_{\infty}\rm [Tb(Tz\ast)_{3}]$ is a 2‐dimensional framework with a (6,6) topology including (Tz*)– double bridges. The structure can be deduced from a basic structure type as it adopts the AlCl3 structure with the triazolate ligands establishing the package. (Tz*)– thus function as μ‐η1:η2/μ‐η2:η1 linkers between trivalent terbium ions that have a C.N. of nine. The framework exhibits an exceptional thermal stability up to 380 °C considering the three neighbouring nitrogen atoms of the triazolate ligands. At this point the framework decomposes in one single exothermic step under release of N2.
Metal(II) Cyamelurates Prepared from Aqueous Ammonia
Authors: Sattler Andreas , Budde Michael R. , Schnick Wolfgang
Published: April 2009

We identified three metal(II) salts of cyameluric acid, namely CaNH4(H2C6N7O3)(HC6N7O3)·6H2O, [Cu(NH3)2]3(C6N7O3)2·2H2O and (NH4)2[Zn(H2O)6](HC6N7O3)2·2H2O. All three compounds were prepared by crystallization from aqueous ammonia solutions containing the respective metal(II) ions. Apparently, the copper salt is identical with a compound claimed in the literature with formula CuNH4C6N7O3·NH3. We studied the structure of all three compounds using single‐crystal XRD (CaNH4(H2C6N7O3)(HC6N7O3)·6H2O: P\bar{1} (no. 2), a = 6.6428(13), b = 8.7159(17), c = 19.245(4) Å, α = 92.52(3), β = 92.22(3), γ = 106.95(3)°, V = 1063.3(4) Å3, Z = 2), ([Cu(NH3)2]3(C6N7O3)2·2H2O: P\bar{1} (no. 2), a = 7.1732(14), b = 9.2338(18), c = 9.994(2) Å, α = 94.15(3), β = 106.13(3), γ = 106.28(3)°, V = 602.3(3) Å3, Z = 1), ((NH4)2[Zn(H2O)6](HC6N7O3)2·2H2O: P\bar{1} (no. 2), a = 6.7568(14), b = 8.7252(17), c = 10.505(2) Å, α = 77.03(3), β = 77.08(3), γ = 82.95(3)°, V = 586.5(2) Å3, Z = 1). With the present work we provide the first structural investigation of cyamelurate salts containing divalent metal ions. We studied the occurrence of special structural features for the title compounds which have been claimed for copper salts of cyameluric acid by earlier works. We also made some fundamental discoveries about the crystal growth in these systems. The copper compound was studied further, using magnetic measurements and thermal analysis.
Hyperparathyroidism and Malnutrition with Severe Vitamin D Deficiency
Authors: Agarwal Amit , Gupta Sushil Kumar , Sukumar Ranjith
Published: April 2009

Background

Vitamin D deficiency and its associated problems are common in developing Asian countries and countries of the Middle East. Various factors, including poor nutritional status and other compounding factors such as dietary, cultural, ethnic, and environmental factors, play a major role in contributing to the poor calcium and vitamin D homeostasis. Vitamin D deficiency is thought to exacerbate signs and symptoms of hyperparathyroidism (HPT). In this overview, we present evidence of the impact of vitamin D and calcium deficiency on primary HPT (PHPT).

Methods

We performed an evidence‐based review of articles published in the English language between January 1960 and June 2008.

Results

Level IV evidence suggests widespread calcium and vitamin D deficiency in developing countries (issue 1). Limited level IV evidence suggests malnutrition as a primary cause of calcium and vitamin D deficiency (issue 2). Level IV evidence suggests that calcium and vitamin deficiencies cause secondary HPT and possibly PHPT as well (issues 3 and 4). A literature search revealed only six studies that correlated vitamin D levels with clinical, biochemical, and pathologic features of PHPT (issue 5). These studies provide level IV evidence suggesting that vitamin D deficiency causes some specific clinical features of PHPT as well as exacerbating other features of the disease.

Conclusions

In the developing countries, which have severe vitamin D and calcium deficient population, PHPT patients present with advanced disease and particularly severe bone symptoms. There is presently only level IV evidence of vitamin D status affecting the clinical severity of PHPT.
Gastroesophageal Reflux Disease and Morbid Obesity: Is There a Relation?
Authors: Fisichella Piero M. , Patti Marco G.
Published: April 2009

Gastroesophageal reflux disease (GERD) is highly prevalent in morbidly obese patients, and a high body mass index (BMI) is a risk factor for the development of GERD. However, the mechanism by which the BMI affects esophageal acid exposure is not completely understood. Although many advances have been made in the understanding of the pathophysiology of GERD, many aspects of the pathophysiology of this disease in morbidly obese patients remain unclear. The following review describes the current evidence linking esophageal reflux to obesity, covering the pathophysiology of the disease and the implications for treatment of GERD in the obese patient.
Why Are Experts Correlated? Decomposing Correlations Between Judges
Authors: Broomell Stephen B. , Budescu David V.
Published: April 2009

We derive an analytic model of the inter-judge correlation as a function of five underlying parameters. Inter-cue correlation and the number of cues capture our assumptions about the environment, while differentiations between cues, the weights attached to the cues, and (un)reliability describe assumptions about the judges. We study the relative importance of, and interrelations between these five factors with respect to inter-judge correlation. Results highlight the centrality of the inter-cue correlation. We test the model’s predictions with empirical data and illustrate its relevance. For example, we show that, typically, additional judges increase efficacy at a greater rate than additional cues.
Normal growth and development in mice over‐expressing the CCN family member WISP3
Authors: Nakamura Yukio , Cui Yajun , Fernando Carol , Kutz Wendy E. , Warman Matthew L.
Published: April 2009

Loss‐of‐function mutations in the gene WISP3 cause the autosomal recessive human skeletal disease Progressive Pseudorheumatoid Dysplasia, whereas mice with knockout mutations of Wisp3 have no phenotype. The lack of a phenotype in the Wisp3 knockout mice has constrained studies of the protein’s in vivo function. Over‐expression experiments in zebrafish indicated that WISP3 may function as a BMP and Wnt signaling modulator. To determine whether these biologic activities are retained in mice, we created two strains of transgenic mice that over‐express WISP3 in a broad array of tissues. Despite strong and persistent protein over‐expression, the transgenic mice remained phenotypically indistinguishable from their non‐transgenic littermates. Surprisingly, WISP3 contained in conditioned medium recovered from transgenic mouse primary kidney cell cultures was able to bind BMP and to inhibit BMP signaling in vitro. Factors that account for the difference between the in vitro and in vivo activities of WISP3 remain unknown. At present, the mouse remains a challenging model organism in which to explore the biologic function of WISP3.

Summary of article. Transgenic mice that broadly over‐express WISP3 were created to search for in vivo biologic activities, since mice that lack WISP3 were normal. Surprisingly, transgenic mice were also phenotypically indistinguishable from wild‐type animals. The mouse is a challenging model organism in which to explore the biologic function of WISP3.
La descente infinie, l’induction transfinie et le tiers exclu
Authors: Gauthier Yvon
Published: April 2009

RÉSUMÉ : Cet article propose que l’équivalence postulée entre la descente infinie et l’induction transfinie dans les fondements de l’arithmétique fait intervenir le principe du tiers exclu par la double négation sur l’ensemble infini des nombres naturels et ne saurait donc être admissible du point de vue de la logique et des mathématiques intuitionnistes. Si, par ailleurs, on adopte le point de vue de la logique classique, les principes de l’induction complète, de l’induction transfinie, du plus petit nombre et de la descente infinie sont tous équivalents; pourtant, la descente infinie en jeu dans l’arithmétique ensembliste de Dedekind-Peano ne correspond pas à la descente infinie de Fermat en théorie des nombres et en arithmétique classique de Gauss jusqu’à nos jours. C’est là le point d’ancrage d’une critique fondationnelle qui cherche à mieux définir les options philosophiques dans les fondements de la logique et des mathématiques.
Is Society-Centered Moral Theory a Contemporary Version of Natural Law Theory?
Authors: Copp David
Published: April 2009

ABSTRACT: David Braybrooke argues that the core of the natural law theory of Thomas Aquinas survived in the work of Hobbes, Locke, Hume, and Rousseau. Much to my surprise, Braybrooke argues as well that David Copp’s society-centered moral theory is a secular version of this same natural law theory. Braybrooke makes a good case that there is an important idea about morality that is shared by the great philosophers in his group and that this idea is also found in Copp’s work. The idea is captured by the Functionalist Thesis, the thesis that moral propositions are made true by facts about what, given the nature of human beings and their circumstances, enables people to live together in thriving communities. I argue that Copp can accept Braybrooke’s suggestion and use it to improve his formulation of the basic idea of the society-centered theory.
Hume’s Causal Reconstruction of the Perceptual Relativity Argument inTreatise1.4.4
Authors: Butler Annemarie
Published: April 2009

ABSTRACT: In Treatise 1.4.4, on behalf of modern philosophers, Hume described a causal argument that shows that our impressions of secondary qualities do not resemble qualities of objects themselves. However, in their respective arguments, Hume’s philosophical predecessors did not argue causally, but appealed to contrary qualities. I argue that Hume’s presentation was not simply a “gratuitous” stylistic difference, but an important correction of his predecessors in light of his own philosophical discoveries.
Aspects cognitifs en logique intensionnelle et théorie de la vérité
Authors: Vanderveken Daniel
Published: April 2009

RÉSUMÉ : Dans l’optique de la recherche d’un critère plus fin d’identité propositionnelle pour une analyse adéquate du sens et de la pensée, je propose une révision de l’ontologie de la théorie des types de sens et de dénotations de Frege et Church, et je formule une logique naturelle prédicative des propositions qui explique leur forme logique en termes d’actes de prédication. Je définis en outre la notion plus subjective de vérité selon un agent ainsi qu’une nouvelle notion d’implication propositionnelle forte. La logique intensionnelle ainsi préconisée explique pourquoi les agents humains sont pourvus d’une rationalité minimale. Je conclus par la présentation d’une nouvelle axiomatisation de la logique épistémique minimale.
Explaining the Qualitative Dimension of Consciousness: Prescission Instead of Reification
Authors: Champagne Marc
Published: April 2009

ABSTRACT: This paper suggests that it is largely a want of notional distinctions which fosters the “explanatory gap” that has beset the study of consciousness since T. Nagel’s revival of the topic. Modifying Ned Block’s controversial claim that we should countenance a “phenomenal-consciousness” which exists in its own right, we argue that there is a way to recuperate the intuitions he appeals to without engaging in an onerous reification of the facet in question. By renewing with the full type/token/tone trichotomy developed by C. S. Peirce, we think the distinctness Block (rightly) calls attention to can be seen as stemming not from any separate module lurking within the mind, but rather from our ability toprescindqualities from occurrences.