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Burkholderia species use BimA for intracellular actin-based motility. Uniquely, Burkholderia thailandensis BimA harbors a central and acidic (CA) domain. The CA domain was required for aetin-based motility, binding to the cellular Arp2/3 complex, and Arp2/3-dependent polymerization of actin monomers. Our data reveal distinct strategies for actin-based motility among Burkholderia species. doi: 10.1128/JB.00608-10

The leptin receptor (LEPR) is associated with insulin resistance, a key feature of metabolic syndrome (MetS). Gene- fatty acid interactions may affect MetS risk. The objective was to investigate the relationship among LEPR polymorphisms, insulin resistance, and MetS risk and whether plasma fatty acids, a biomarker of dietary fatty acids, modulate this. LEPR polymorphisms (rs10493380, rs1137100, rs1137101, rs12067936, rs1805096, rs2025805, rs3790419, rs3790433, rs6673324, and rs8179183), biochemical measurements, and plasma fatty acid profiles were determined in the LIPGENE-SU.VI.MAX study of MetS cases and matched controls (n = 1754). LEPR rs3790433 GG homozygotes had increased MetS risk compared with the minor A allele carriers [odds ratio (OR) = 1.65; 95% CI: 1.05-2.57; P = 0.028], which may be accounted for by their increased risk of elevated insulin concentrations (OR 2.40; 95% CI: 1.28-4.50; P= 0.006) and insulin resistance (OR = 2.15; 95% CI: 1.18-3.90; P= 0.012). Low (less than median) plasma (n-3) and high (n-6) PUFA status exacerbated the genetic risk conferred by GG homozygosity to hyperinsulinemia (OR 2.92-2.94) and insulin resistance (OR 3.40-3.47). Interestingly, these associations were abolished against a high (n-3) or low (n-6) PUFA background. Importantly, we replicated some of these findings in an independent cohort. Homozygosity for the LEPR rs3790433 G allele was associated with insulin resistance, which may predispose to increased MetS risk. Novel gene-nutrient interactions between LEPR rs3790433 and PUFA suggest that these genetic influences were more evident in individuals with low plasma (n-3) or high plasma (n-6) PUFA. J. Nutr. 140: 238-244, 2010. doi: 10.3945/jn.109.115329.

Signal transducer and activator of transcription 3 (STAT3) plays a key role in body weight regulation and glucose homeostasis, 2 important determinants of metabolic syndrome (MetS). Dietary fat is a key environmental factor that may interact with genotype to affect MetS risk. In this study, we investigated the relationship between STAT3 polymorphisms and MetS phenotypes and determined potential interactions with dietary fatty acids. STAT3 polymorphisms (rs8069645, rs744166, rs2306580, rs2293152, and rs10530050), biochemical measurements, and dietary fat composition were determined in the LIPGENE-SU.VI.MAX study of MetS cases and matched controls (n = 1754). STAT3 polymorphisms were not associated with MetS risk. However, minor G allele carriers for rs8069645, rs744166, and rs1053005 and major GG homozygotes for rs2293152 had increased risk of abdominal obesity compared with noncarriers [odds ratio (OR) = 2.22, P = 0.0005; OR = 2.08, P = 0.0017; OR = 2.00, P = 0.0033; and OR = 1.95, P = 0.028, respectively]. The number of risk alleles additively increased obesity risk (P = 0.0003). Dietary SFA intake exacerbated these effects; among all participants with the highest SFA intake (-> 15.5% of energy), individuals carrying >2 risk alleles had further increased risk of obesity (OR = 3.30; 95% CI = 1.50-7.28; P = 0.0079) compared with those carrying - doi: 10.3945/jn.109.100635

Accurate measurement of enzyme kinetics is an essential part of understanding the mechanisms of biochemical reactions. The typical means of studying such systems use stirred cuvettes, stopped-flow apparatus, microfluidic systems, or other small sample containers. These methods may prove to be problematic if reactants or products adsorb to or react with the container's surface. As an alternative approach, we have developed an acoustically-levitated drop reactor eventually intended to study enzyme-catalyzed reaction kinetics related to free radical and oxidative stress chemistry. Microliter-scale droplet generation, reactant introduction, maintenance, and fluid removal are all important aspects in conducting reactions in a levitated drop. A three capillary bundle system has been developed to address these needs. We report kinetic measurements for both luminol chemiluminescence and the reaction of pyruvate with nicotinamide adenine dinucleotide, catalyzed by lactate dehydrogenase, to demonstrate the feasibility of using a levitated drop in conjunction with the developed capillary sample handling system as a microreactor. 10.1021/ac901400y

Statistical analysis and modeling of wireless channels is essential to wireless communication systems. Clarke's model [1] and the corresponding statistical analysis of mobile radio reception has been widely accepted in numerous wireless applications. Since the component phases in Clarke's model are assumed to be constant in time, the well-known results of statistical analysis based on this model, such as the autocorrelation and Doppler power spectrum, are not appropriate to describe real wireless channels for which the random environments (radio propagation paths) are time-varying and accordingly for which the channel is non-constant in the absence of Doppler frequency shift. In this paper, we extend the traditional Clarke's model incorporating the effect of fluctuations in the component phases, and perform the statistical analysis which results in a closed-form expression of the autocorrelation of the fading. The theoretical power spectral density function, which is the Fourier transform of the resultant autocorrelation of the fading, is shown to fit the practical measured spectra, which is in contrast to the traditional theoretical flat fading channel spectra (Jakes' spectrum in [2]). The proposed model and statistical results should have important implications for detailed spectral analysis and channel simulations for real wireless communications systems in random fluctuating electromagnetic propagation environments. Index Terms--Multipath channels, time-varying channels, correlation, Doppler measurements, spectral analysis.

We screened 5,700 Salmonella enterica serovar Typhimurium mutants for defects in type III secretion system 1 (T3SS-1)-mediated contact-dependent hemolysis to identify novel genes and pathways affecting the activity of T3SS-1. Our data suggest that previously unrecognized factors such as type I fimbriae may modulate the expression, activity, or deployment of this key virulence factor.

The ventilation factor and capacitance used in numerical models to represent ice crystal aggregates directly affects the growth rate of the ice crystal aggregates, and consequently the sink of atmospheric water vapor. Currently, numerical models that prognose ice water content (IWC) and water vapor mixing ratio represent the capacitance and ventilation factor of precipitation-sized particles with simplified geometries, such as hexagonal plates. The geometries of actual precipitation-sized particles are often more complex, and a test of the values being employed is needed. Aircraft observations obtained during a Lagrangian spiral descent through the sublimation zone of a tropical anvil cloud have been used to determine an estimate of combined dimensionless capacitance and ventilation factor for the nonpristine geometries exhibited by ice crystal aggregates. By combining measurements of bulk ice water content, the particle size distribution, and environmental subsaturation, the change in ice water content was modeled throughout the spiral descent and compared with observations of the change in ice water content. Uncertainties resulting from potential systematic biases in the measurements and parameterizations used in the analysis were investigated with sensitivity tests. Most of the uncertainty was related to an assumed maximum potential bias in the measurement of IWC of [+ or -] 45%. The resulting combined ventilation factor and dimensionless capacitance value was 1.3 (with a range of 0.6-1.9, defined by 68% of sensitivity test trials) for a particle size-weighted mean value of [(Sc).sup.1/3][(Re).sup.1/2] = 14.9 [+ or -] 1.7, where Sc is the Schmidt number and Re is the Reynolds number. Results from commonly adopted combinations of ventilation factor relations and capacitances are compared with the observations presented here, and, finally, surrogate dimensionless capacitances are suggested that when combined with commonly used ventilation factor relations are consistent with the results presented herein.

A theoretical framework has been developed describing nonequilibrium formation and maintenance of mixed-phase clouds. The necessary and sufficient conditions required to activate liquid water within a preexisting ice cloud, and thus convert it to mixed phase, are considered for three scenarios: (i) uniform ascent, (ii) harmonic vertical oscillations, and (iii) turbulent fluctuations. The general conditions are the following: 1) First necessary condition: The vertical velocity of an ice cloud parcel must exceed a threshold velocity to activate liquid water. 2) Second necessary condition: The activation of liquid water within an ice cloud parcel, below water saturation, requires a vertical ascent above some threshold altitude to bring the vapor pressure of the parcel to water saturation. Only when the first and second conditions are true do these conditions become sufficient for the activation of liquid water in ice clouds. These required conditions for the generation of mixed-phase cloud are supported by parcel modeling results and analogous conditions for a harmonic oscillation concerning the amplitude and tangential velocity of the parcel motion are proposed. The authors do not assume steadystate conditions, but demonstrate that nonequilibrium evolution of cloud parcels can lead to long-term steady existence of mixed-phase cloud.

Many microphysical process rates involving snow are proportional to moments of the snow particle size distribution (PSD), and in this study a moment estimation parameterization applicable to both midlatitude and tropical ice clouds is proposed. To this end aircraft snow PSD data were analyzed from tropical anvils [Tropical Rainfall Measuring Mission/Kwajelein Experiment (TRMM/KWAJEX), Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE)] and midlatitude stratiform cloud [First International Satellite Cloud Climatology Project Research Experiment (FIRE), Atmospheric Radiation Measurement Program (ARM)]. For half of the dataset, moments of the PSDs are computed and a parameterization is generated for estimating other PSD moments when the second moment (proportional to the ice water content when particle mass is proportional to size squared) and temperature are known. Subsequently the parameterization was tested with the other half of the dataset to facilitate an independent comparison. The parameterization for estimating moments can be applied to midlatitude or tropical clouds without requiring prior knowledge of the regime of interest. Rescaling of the tropical and midlatitude size distributions is presented along with fits to allow the user to recreate realistic PSDs given estimates of ice water content and temperature. The effects of using different time averaging were investigated and were found not to be adverse. Finally, the merits of a single-moment snow microphysics versus multimoment representations are discussed, and speculation on the physical differences between the rescaled size distributions from the Tropics and midlatitudes is presented.

Modeling wireless channels is essential to wireless communication systems. An autoregressive (AR) process of order one for wireless channel has long been assumed, but without a rigorous mathematical/physical basis. In this paper, we derive a first-order stochastic AR model for a flat stationary wireless channel, which comes from stochastic differential equation (SDE) theory concerning the nature of multipath fading channels. The resulting AR model describes more of the origin of multipath fading channels than previous AR models, and it can efficiently model and generate Rayleigh-distributed stationary fading channels. The Markovian property of the AR model is inherited through the SDE approach. Index Terms--Autoregressive (AR) process, multipath channels, Rayleigh, stochastic differential equation (SDE).

Ice particle size distributions (PSDs) can be scaled onto a single exponential distribution for a wide range of observed conditions as demonstrated using data from Atmospheric Research Measurement (ARM) cirrus uncinus, Tropical Rainfall Measurement Mission (TRMM) tropical anvils, and First International Satellite Cloud Climatalogy Project (ISCCP) Regional Experiment (FIRE1) midlatitude cirrus field programs. The successful scaling of the PSDs is the result of the dominance of the aggregation process. The PSD is found to be a function of mean particle size and precipitation rate only. A correlation between precipitation rate and particle mass and fall speed relations is demonstrated and made use of in a semiempirical model of ice cloud that predicts the evolution of PSDs.

This study reports on the evolution of particle size distributions (PSDs) and habits as measured during slow, Lagrangian-type spiral descents through deep subtropical and tropical cloud layers in Florida, Brazil, and Kwajalein, Marshall Islands, most of which were precipitating. The objective of the flight patterns was to learn more about how the PSDs evolved in the vertical and to obtain information of the vertical structure of microphysical properties. New instrumentation yielding better information on the concentrations of particles in the size (D) range between 0.2 and 2 cm, as well as improved particle imagery, produced more comprehensive observations for tropical stratiform precipitation regions and anvils than have been available previously. Collocated radar observations provided additional information on the vertical structure of the cloud layers sampled. Most of the spirals began at cloud top, with temperatures (T) as low as -50[degrees]C, and ended at cloud base or below the melting layer (ML). The PSDs broadened from cloud top toward cloud base, with the largest particles increasing in size from several millimeters at cloud top, to 1 cm or larger toward cloud base. Some continued growth was noted in the upper part of the ML. Concentrations of particles less than 1 mm in size decreased with decreasing height. The result was a consistent change in the PSDs in the vertical. Similarly, systematic changes in the size dependence of the particle cross-sectional area was noted with decreasing height. Aggregation--as ascertained from both the changes in the PSDs and evolution of particle habits as observed in high detail with the cloud particle imager (CPI) probe--was responsible for these trends. The PSDs were generally well-represented by gamma distributions of the form N = [N.sub.0[GAMMA]][D.sup.mu][e.sup.-[lambda][GAMMA]]D that were fitted to the PSDs over 1-km horizontal intervals throughout the spirals. The intercept ([N.sub.0[GAMMA]]), slope ([[lambda].sub.[GAMMA]]), and dispersion ([mu]) values were derived for each PSD. Exponential curves (N = [N.sub.0][e.sup.-[lambda]D]; [mu] = 0) were also fitted to the distributions. The [[lambda].sub.[GAMMA]] values for given spirals varied systematically with temperature as did the values of [lambda] (exponential), and the data generally conformed to values found in previous studies involving exponential fits to size distributions in midlatitude frontal and cirrus layers. Considerable variability often noted in the PSD properties during the loops of individual spirals was manifested primarily in large changes in [N.sub.0[GAMMA]] and [N.sub.0], but [mu], [[lambda].sub.[GAMMA]], and [lambda] remained fairly stable. Temperature is not found to be the sole factor controlling [[lambda].sub.[GAMMA]] or [lambda], but is a primary one. Direct relationships were found between [[lambda].sub.[GAMMA]] and [N.sub.0[GAMMA]], or [[lambda].sub.[GAMMA]] and [mu], for the gamma distributions, and [lambda] and [N.sub.0] for the exponential. The latter relationship was not found as distinctly in earlier studies; observed PSDs in this study had better fidelity with less scatter. The [mu] values changed monotonically with T over the range of temperatures .and were directly related to [N.sub.0[GAMMA]] or [[lambda].sub.[GAMMA]], thereby reducing the number of variables in the PSD functional equation to two. In the upper part of the ML, [N.sub.0], and A continued to decrease, and in the lower part these values began to increase as the largest particles melted. General expressions relating various bulk microphysical, radar, and radiative-transfer-related variables to [N.sub.0[GAMMA]] and [[lambda].sub.[GAMMA]] were developed; they are useful for both tropical and midlatitude clouds. These relationships facilitate the specification of a number of bulk properties in cloud and climate models. The results presented in this paper apply best to temperatures between 0[degrees] and -40[degrees]C, for which the measured radar reflectivities fall in the range of 0 to 25 dB[Z.sub.e].