Mathematical model of mechanical behavior of micro/nanofibrous materials designed for extracellular matrix substitutes

Electrospun micro/nanofibrous biomaterials are widely used as extracellular matrix substitutes in tissue engineering applications because of their structural and mechanical properties. To explore the influence of microstructure on the mechanical behavior of fibrous material, a mathematical model of the fiber system was developed. The model describes the microstructural properties of a fibrous matrix using a probability density function, and enables study of their mechanical properties. The results from the mathematical model were validated by qualitative comparison with the experimental results of mechanical testing of polystyrene electrospun nanofibrous materials. The analyses show a trend of three-phase load-displacement behavior. Initially, as an increasing number of fibers are recruited for load bearing, the load-displacement curve has a 'J'-shaped toe region, which is followed by a nearly linear load-displacement curve, in which the number of load-bearing fibers remains nearly steady. Finally, there is a phase when the load-displacement curve descends, indicating failure of the material. The increase in flexibility of the fibrous material makes it stronger, but the randomness of fiber orientation makes the fibrous structure more flexible at the cost of lower strength. The measured mechanical properties of a fibrous matrix were also observed to be dependent on sample size. Therefore, the analyses establish a clear link between the structure and strength of fibrous materials for optimized design and fabrication of fibrous biomaterials with targeted use in tissue engineering, regenerative medicine and drug delivery. The model also establishes a need for standardization of experimental protocols for mechanical characterization of fibrous materials for consistency.

Search for the standard model Higgs boson in associated WH production in 9.7 fb(-1) of pp collisions with the D0 detector

We present a search for the standard model Higgs boson in final states with a charged lepton (electron or muon), missing transverse energy, and two or three jets, at least one of which is identified as a b-quark jet. The search is primarily sensitive to WH→ℓνbb production and uses data corresponding to 9.7 fb(-1) of integrated luminosity collected with the D0 detector at the Fermilab Tevatron pp Collider at √s = 1.96 TeV. We observe agreement between the data and the expected background. For a Higgs boson mass of 125 GeV, we set a 95% C.L. upper limit on the production of a standard model Higgs boson of 5.2 × σ(SM), where σ(SM) is the standard model Higgs boson production cross section, while the expected limit is 4.7 × σ(SM).

Combined search for the standard model Higgs boson decaying to bb using the D0 run II data set

We present the results of the combination of searches for the standard model Higgs boson produced in association with a W or Z boson and decaying into bb using the data sample collected with the D0 detector in pp collisions at √s = 1.96 TeV at the Fermilab Tevatron Collider. We derive 95% C.L. upper limits on the Higgs boson cross section relative to the standard model prediction in the mass range 100 GeV ≤ M(H) ≤ 150 GeV, and we exclude Higgs bosons with masses smaller than 102 GeV at the 95% C.L. In the mass range 120 GeV ≤ M(H) ≤145 GeV, the data exhibit an excess above the background prediction with a global significance of 1.5 standard deviations, consistent with the expectation in the presence of a standard model Higgs boson.

Search for the standard model Higgs boson in ZH→ℓ(+)ℓ(-)bb production with the D0 detector in 9.7 fb(-1) of pp collisions at √s = 1.96 TeV

We present a search for the standard model (SM) Higgs boson produced in association with a Z boson in 9.7 fb(-1) of pp collisions collected with the D0 detector at the Fermilab Tevatron Collider at √s = 1.96 TeV. Selected events contain one reconstructed Z→e(+)e(-) or Z→μ(+)μ(-) candidate and at least two jets, including at least one jet identified as likely to contain a b quark. To validate the search procedure, we also measure the cross section for ZZ production in the same final state. It is found to be consistent with its SM prediction. We set upper limits on the ZH production cross section times branching ratio for H→bb at the 95% C.L. for Higgs boson masses 90 ≤ M(H) ≤ 150 GeV. The observed (expected) limit for M(H) = 125 GeV is 7.1 (5.1) times the SM cross section.

Evidence for a particle produced in association with weak bosons and decaying to a bottom-antibottom quark pair in higgs boson searches at the tevatron

We combine searches by the CDF and D0 Collaborations for the associated production of a Higgs boson with a W or Z boson and subsequent decay of the Higgs boson to a bottom-antibottom quark pair. The data, originating from Fermilab Tevatron pp collisions at √s = 1.96 TeV, correspond to integrated luminosities of up to 9.7 fb(-1). The searches are conducted for a Higgs boson with mass in the range 100-150 GeV/c(2). We observe an excess of events in the data compared with the background predictions, which is most significant in the mass range between 120 and 135 GeV/c(2). The largest local significance is 3.3 standard deviations, corresponding to a global significance of 3.1 standard deviations. We interpret this as evidence for the presence of a new particle consistent with the standard model Higgs boson, which is produced in association with a weak vector boson and decays to a bottom-antibottom quark pair.

Membrane-damaging potential of natural L-(-)-usnic acid in Staphylococcus aureus

The purpose of this investigation was to try to understand the antibacterial mechanism of L-(-)-usnic acid isolated for the first time from fruticose lichen Usnea subfloridana using clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA). The minimum inhibitory concentration (MIC) of L-(-)-usnic acid against the clinical isolates of MRSA and reference strain S. aureus MTCC-96 (SA-96) was in the range 25-50 μg/ml. Treatment of both reference and clinical strains (MRSA-ST 2071) with four-fold MIC concentrations (100-200 μg/ml) of L-(-)-usnic acid reduced the viability of cells without damaging the cell wall. However, the loss of 260 nm absorbing material and increase in propidium iodide uptake was observed in both of the strains. Similarly, a combined effect of L-(-)-usnic acid (25-50 μg/ml) and 7.5 % NaCl resulted in a reduced number of viable cells within 24 h in comparison to the control. These observations clearly indicate that L-(-)-usnic acid exerts its action by disruption of the bacterial membrane. Further, in vivo efficacy showed that L-(-)-usnic acid significantly (p < 0.001) lowered the microbial load of spleen at doses ranging from 1 to 5 mg/kg. Further, toxicity studies in infected mice at doses 20 times higher than the efficacious dose indicated L-(-)usnic acid to be safe. Paradoxically, L-(-)usnic acid exhibited changes in serum triglycerides, alkaline phosphatase (ALKP) and liver organ weight in the healthy mice administered with only 25 mg/kg body weight. The results obtained in this study showed that natural L-(-)-usnic acid exerts its antibacterial activity against MRSA by disruption of the cell membrane. Further, the natural L-(-)-usnic acid was found to be safe up to 100 mg/kg body weight, thereby, making it a probable candidate for treating S. aureus infections.

The gastro-esophageal reflux barrier: biophysical analysis on 3D models of anatomy from magnetic resonance imaging

BACKGROUND

The function and structure of the gastro-esophageal junction (GEJ) determine its efficacy as a reflux barrier. This study presents a novel methodology for the quantitative assessment of GEJ and proximal gastric morphology from magnetic resonance (MR) imaging. Based on this data we propose a new conceptualization of the hypothesis that a flap valve mechanism contributes to reflux protection.

METHODS

3D models of the GEJ and proximal stomach were reconstructed from MR images in 12 healthy volunteers during respiration and on eating a test meal to maximum satiation. A rotating plane analysis measured the gastro-esophageal insertion angle and span of contact. An ellipsoid fit provided quantitative assessment of gastric shape and orientation relative to a fixed anatomical reference point. Position of the esophageal insertion on the 'gastric ellipse' was noted. An ellipsoid-cylinder model was designed to analyze the relationships among parameters describing the GEJ morphology.

KEY RESULTS

The insertion angle became more acute on expiration, but did not change with meal ingestion. In contrast the span of contact did not vary with respiration, but increased with gastric filling. Changes in gastric morphology with distension further augmented the span of gastro-esophageal contact in almost 70% of the studies.

CONCLUSIONS & INFERENCES

Novel MR imaging and biophysical analysis of the GEJ and proximal stomach provide a quantitative description of structures contributing to the reflux barrier. Changes in these parameters during respiration and on eating support the hypothesis that structural components of a functional 'flap valve' like mechanism contribute to reflux protection.

Search for violation of Lorentz invariance in top quark pair production and decay

Using data collected with the D0 detector at the Fermilab Tevatron Collider, corresponding to 5.3 fb(-1) of integrated luminosity, we search for violation of Lorentz invariance by examining the tt[over ¯] production cross section in lepton+jets final states. We quantify this violation using the standard-model extension framework, which predicts a dependence of the tt[over ¯] production cross section on sidereal time as the orientation of the detector changes with the rotation of the Earth. Within this framework, we measure components of the matrices (c(Q))(μν33) and (c(U))(μν33) containing coefficients used to parametrize violation of Lorentz invariance in the top quark sector. Within uncertainties, these coefficients are found to be consistent with zero.

Measurements of WW and WZ production in W + jets final states in pp collisions

We study WW and WZ production with ℓνqq (ℓ=e,μ) final states using data collected by the D0 detector at the Fermilab Tevatron Collider corresponding to 4.3  fb(-1) of integrated luminosity from pp collisions at sqrt[s]=1.96  TeV. Assuming the ratio between the production cross sections σ(WW) and σ(WZ) as predicted by the standard model, we measure the total WV (V=W,Z) cross section to be σ(WV)=19.6(-3.0)(+3.2)  pb and reject the background-only hypothesis at a level of 7.9 standard deviations. We also use b-jet discrimination to separate the WZ component from the dominant WW component. Simultaneously fitting WW and WZ contributions, we measure σ(WW)=15.9(-3.2)(+3.7)  pb and σ(WZ)=3.3(-3.3)(+4.1)  pb, which is consistent with the standard model predictions.

Measurement of the W boson mass with the D0 detector

We present a measurement of the W boson mass using data corresponding to 4.3  fb(-1) of integrated luminosity collected with the D0 detector during Run II at the Fermilab Tevatron pp collider. With a sample of 1,677,394 W → eν candidate events, we measure M(W) = 80.367 ± 0.026  GeV. This result is combined with an earlier D0 result determined using an independent Run II data sample, corresponding to 1  fb(-1) of integrated luminosity, to yield M(W) = 80.375 ± 0.023  GeV.

Search for universal extra dimensions in pp collisions

We present a search for Kaluza-Klein (KK) particles predicted by models with universal extra dimensions (UED) using a data set corresponding to an integrated luminosity of 7.3 fb(-1), collected by the D0 detector at a pp center-of-mass energy of 1.96 TeV. The decay chain of KK particles can lead to a final state with two muons of the same charge. This signature is used to set a lower limit on the compactification scale of R(-1)>260 GeV in a minimal UED model.

Search for charged massive long-lived particles

We report on a search for charged massive long-lived particles (CMLLPs), based on 5.2  fb(-1) of integrated luminosity collected with the D0 detector at the Fermilab Tevatron pp collider. We search for events in which one or more particles are reconstructed as muons but have speed and ionization energy loss (dE/dx) inconsistent with muons produced in beam collisions. CMLLPs are predicted in several theories of physics beyond the standard model. We exclude pair-produced long-lived gauginolike charginos below 267 GeV and Higgsino-like charginos below 217 GeV at 95% C.L., as well as long-lived scalar top quarks with mass below 285 GeV.

Evidence for spin correlation in t ̅t production

We present a measurement of the ratio of events with correlated t and t ̅t spins to the total number of t ̅t events. This ratio f is evaluated using a matrix-element-based approach in 729 t ̅t candidate events with a single lepton ℓ (electron or muon) and at least four jets. The analyzed p ̅p collisions data correspond to an integrated luminosity of 5.3 fb(-1) and were collected with the D0 detector at the Fermilab Tevatron collider operating at a center-of-mass energy √s=1.96 TeV. Combining this result with a recent measurement of f in dileptonic final states, we find f in agreement with the standard model. In addition, the combination provides evidence for the presence of spin correlation in t ̅t events with a significance of more than 3 standard deviations.

Search for doubly charged Higgs boson pair production in pp¯ collisions at √s=1.96 TeV

We present a search for pair production of doubly charged Higgs bosons in the processes qq¯→H(++)H(--) decaying through H(±±)→τ(±)τ(±),μ(±)τ(±),μ(±)μ(±). The search is performed in pp¯ collisions at a center-of-mass energy of √s = 1.96 TeV using an integrated luminosity of up to 7.0 fb(-1) collected by the D0 experiment at the Fermilab Tevatron Collider. The results are used to set 95% C.L. limits on the pair production cross section of doubly charged Higgs bosons and on their mass for different H(±±) branching fractions. Models predicting different H(±±) decays are investigated. Assuming B(H(±±)→τ(±)τ(±))=1 yields an observed (expected) lower limit on the mass of a left-handed H(L)(±±) boson of 128 (116) GeV and assuming B(H(±±)→μ(±)τ(±))=1 the corresponding limits are 144 (149) GeV. In a model with B(H(±±)→τ(±)τ(±))=B(H(±±)→μ(±)τ(±))=B(H(±±)→μ(±)μ(±))=1/3, we obtain M(H(L)(±±))>130 (138) GeV.

Wγ production and limits on anomalous WWγ couplings in pp collisions at sqrt[s] = 1.96 TeV

We measure the cross section and the difference in rapidities between photons and charged leptons for inclusive W(→lν) + γ production in eγ and μγ final states. Using data corresponding to an integrated luminosity of 4.2  fb(-1) collected with the D0 detector at the Fermilab Tevatron Collider, the measured cross section times branching fraction for the process pp → Wγ + X → lνγ + X and the distribution of the charge-signed photon-lepton rapidity difference are found to be in agreement with the standard model. These results provide the most stringent limits on anomalous WWγ couplings for data from hadron colliders: -0.4<Δκ(γ)<0.4 and -0.08<λ(γ)<0.07 at the 95% C.L.

Effects of aromatase inhibitor on menopausal hyperplasia in a case of obesity

The aromatase inhibitor anastrazole proved effective in the treatment of endometrial hyperplasia and postmenopausal bleeding in an obese 65-year-old woman with high operative risk. During anastrazole administration for 12 months, the endometrial thickness decreased from 9.8 mm to 2.4 mm and the control endometrial histology showed an atrophic endometrium. Uterine bleeding did not occur in the post-treatment, 3-year follow-up period. The endometrial thicknesses measured yearly by ultrasonography were 2.9, 3.5 and 3.3 mm. The plasma estradiol levels increased from < 73 pmol/l post-treatment to 112, 98 and 103 pmol/l. This case demonstrates that long-term aromatase inhibitor treatment can result in a refractory status of the endometrium and the estradiol produced in the adipose tissue does not exert a proliferative effect.