A compact miniaturized continuous flow system for the determination of urea content in milk

A multicommutation-based flow system with photometric detection was developed, employing an analytical microsystem constructed with low temperature co-fired ceramics (LTCC) technology, a solid-phase reactor containing particles of Canavalia ensiformis DC (urease source) immobilized with glutaraldehyde, and a mini-photometer coupled directly to the microsystem which monolithically integrates a continuous flow cell. The determination of urea in milk was based on the hydrolysis of urea in the solid-phase reactor and the ammonium ions produced were monitored using the Berthelot reaction. The analytical curve was linear in the urea concentration range from 1.0 × 10⁻⁴ to 5.0 × 10⁻³ mol L⁻¹ with a limit of detection of 8.0 × 10⁻⁶ mol L⁻¹. The relative standard deviation (RSD) for a 2.0 × 10⁻³ mol L⁻¹ urea solution was lower than 0.4% (n = 10) and the sample throughput was 13 h⁻¹. To check the reproducibility of the flow system, calibration curves were obtained with freshly prepared solutions on different days and the RSD obtained was 4.7% (n = 6). Accuracy was assessed by comparing the results of the proposed method with those from the official procedure and the data are in close agreement, at a 95% confidence level.     

Influence of the zirconia transformation on the thermal behavior of zircon–zirconia composites

During a heating?Ccooling cycle, zirconia (ZrO₂) undergoes a martensitic transformation from monoclinic to tetragonal structure phases, which presents special hysteresis loop in the dilatometry curve at temperatures between 800 and 1100?°C. Monoclinic zirconia (m-ZrO₂) particles reinforced ceramic matrix composites not always present this behavior. In order to elucidate this fact a series of zircon?Czirconia (ZrSiO₄?CZrO₂) ceramic composites have been obtained by slip casting and characterized. The final properties were also correlated with the zirconia content (0?C30?vol.%). The influence of the martensitic transformation (m?Ct) in well-dispersed zirconia grains ceramic composite on the thermal behavior was analyzed. Thermal behavior evaluation was carried out; the correlation between the thermal expansion coefficients with the zirconia content showed a deviation from the mixing rule applied. A hysteresis loop was observed in the reversible dilatometric curve of composites with enough zirconia grains (??10?vol.%). Over this threshold the zirconia content is correlated with the loop area. The transformation temperatures were evaluated and correlated with the zirconia addition. When detected the m?Ct temperature transformation is slightly influenced by the zirconia content (due to the previously evaluated decrease in the material stiffness) and similar to the temperature reported in literature. The reverse (cooling) transformation temperature is strongly decreased by the ceramic matrix. The DTA results are consistent with the dilatometric analysis, but this technique showed more reliable results. Particularly the endothermic m?Ct transformation temperature showed to be easily detected even when the only m-ZrO₂ present was the product of the slight thermal dissociation of the zircon during the processing of the pure zircon material.     

Search for the standard model Higgs boson in the decay channel H→ZZ→4ℓ in pp collisions at √s=7 TeV

A search for a Higgs boson in the four-lepton decay channel H→ZZ, with each Z boson decaying to an electron or muon pair, is reported. The search covers Higgs boson mass hypotheses in the range of 110100 GeV (with 13 below 160 GeV), while 67.1±6.0 (9.5±1.3) events are expected from background. The four-lepton mass distribution is consistent with the expectation of standard model background production of ZZ pairs. Upper limits at 95% confidence level exclude the standard model Higgs boson in the ranges of 134-158 GeV, 180-305 GeV, and 340-465 GeV. Small excesses of events are observed around masses of 119, 126, and 320 GeV, making the observed limits weaker than expected in the absence of a signal.     

Search for signatures of extra dimensions in the diphoton mass spectrum at the large hadron collider

A search for signatures of extra spatial dimensions in the diphoton invariant-mass spectrum has been performed with the CMS detector at the LHC. No excess of events above the standard model expectation is observed using a data sample collected in proton-proton collisions at √s=7 TeV corresponding to an integrated luminosity of 2.2 fb(-1). In the context of the large-extra-dimensions model, lower limits are set on the effective Planck scale in the range of 2.3-3.8 TeV at the 95% confidence level. These limits are the most restrictive bounds on virtual-graviton exchange to date. The most restrictive lower limits to date are also set on the mass of the first graviton excitation in the Randall-Sundrum model in the range of 0.86-1.84 TeV, for values of the associated coupling parameter between 0.01 and 0.10.     

Investigation of fundamental transport properties and thermodynamics in diglyme-salt solutions

Ionic mobility, the thermodynamics of ionic association, and the structure of associated species are studied in solutions of diglyme containing either lithium triflate or tetrabutylammonium triflate. Infrared spectroscopic, PFG NMR, thermodynamic, and crystallographic data suggest that the solute species existing in diglyme-lithium triflate are "free" ions, contact ion pairs, and dimers. Equilibrium constants, S(o), deltaH(o), and deltaG(o) are calculated for processes occurring between these species. In particular, the equilibrium constant, corrected for nonideality using a modified Debye-Hückel expression, is calculated for the dissociation of contact ion pairs into "free" cations and anions. A second equilibrium constant for the formation of dimers from contact ion pairs is also calculated; these constants do not significantly vary with salt concentration up to about 1.3 x 10(-3) mol cm(-3). The measured temperature dependence of equilibrium constants was used to calculate deltaH(o) and deltaS(o) for the two processes. The value of deltaS(o) = -102 J mol(-1) K(-1) for the dissociation of contact ion pairs shows that the large entropy decrease due to cation solvation outweighs the entropy increase due to dissociation of a contact ion pair. Ionic mobilities are calculated in lithium triflate-diglyme solutions using conductivity data in conjunction with information about the nature and concentrations of solute species obtained from IR spectroscopy. Mobilities in tetrabutlyammonium triflate-diglyme solutions are calculated directly from conductivity data. It was concluded that the concentration dependence of the molar conductivity is due in large part to the variation of the ion mobilities with concentration.     

Synthesis and characterization of palladium(II) complexes with new diphosphonium-diphosphine and diphosphine ligands. Production of low molecular weight alternating polyketones via catalytic CO/ethene copolymerisation

The bis-cationic diphosphonium-diphosphine 6,7-di(di-2-methoxyphenyl)phosphinyl-2,2,4,4-tetra(di-2-methoxyphenyl)-2 lambda 4,4 lambda 4-diphosphoniumbicyclo[3.1.1]heptane-bis(PF6) ((o-MeO-PCP)(PF6)2) and the diphosphine rac-2,4-bis((di-2-methoxyphenyl)phosphino)pentane (rac-o-MeO-bdpp) have been synthesized. Both ligands have been employed to coordinate PdCl2 and Pd(OAc)2 to give [PdCl2(o-MeO-PCP)](PF6)2 (1a), PdCl2(rac-o-MeO-bdpp) (1b), [Pd(OAc)2(o-MeO-PCP)](PF6)2 (2a) and Pd(OAc)2(rac-o-MeO-bdpp) (2b). The ligands and complexes have been fully characterized in solution by multinuclear NMR spectroscopy. In addition, 1a and 1b have been authenticated by single crystal X-ray structure analyses. The Pd(II) complexes 1a and 1b have been employed as catalyst precursors for the CO/ethene copolymerisation in water-acetic acid mixtures, while 2a and 2b have been tested in methanol in the presence of p-toluenesulfonic acid. Irrespective of the reaction media, perfectly alternating polyketones were obtained in excellent yields and with number-average molecular weights ranging from 7.1-13.9 kg mol(-1) with the diphosphonium-diphosphine catalysts and from 37.2-48.2 kg mol(-1) with the diphosphine catalysts.     

The influence of poly(ethylene oxide) and illumination on the copper electrodeposition process onto n-Si(100)

In this study, we examined the influence of illumination and the presence of poly(ethylene oxide) (PEO) as an additive for the copper electrodeposition process onto n-Si(100). The study was carried out by means of cyclic voltammetry (CV) and the potential steps method, from which the corresponding nucleation and growth mechanism (NGM) were determined. Likewise, a morphologic analysis of the deposits obtained at different potential values by means of atomic force microscopy (AFM) was carried out. In a first stage, Mott-Schottky measurements so as to characterize the energetics of the semiconductor/electrolyte interface were made. Also, parallel capacity measurements were carried out in order to determine the surface state density of the substrate. It was found that when PEO concentration is increased, the number of these surface states decreases. The CV results indicated that the presence of PEO inhibits the photoelectrochemical reaction of oxide formation on the surface of the semiconductor. This allows a decrease in the overpotential associated with the electrodeposition process. The analysis of the j/t transients shows that the NGM corresponds to progressive three-dimensional (3D) diffusional controlled (PN3D(Diff)), which was confirmed by the AFM technique. Neither illumination nor the presence of PEO changes the mechanisms. Their influence is in that they diminish the size of the nuclei and the speed with which these are formed, which produces a more homogeneous electrodeposit.     

Search for quark compositeness with the dijet centrality ratio in pp collisions at √s=7 TeV

A search for quark compositeness in the form of quark contact interactions, based on hadronic jet pairs (dijets) produced in proton-proton collisions at √s=7 TeV, is described. The data sample of the study corresponds to an integrated luminosity of 2.9 pb(-1) collected with the CMS detector at the LHC. The dijet centrality ratio, which quantifies the angular distribution of the dijets, is measured as a function of the invariant mass of the dijet system and is found to agree with the predictions of the standard model. A statistical analysis of the data provides a lower limit on the energy scale of quark contact interactions. The sensitivity of the analysis is such that the expected limit is 2.9 TeV; because the observed value of the centrality ratio at high invariant mass is below the expectation, the observed limit is 4.0 TeV at the 95% confidence level.     

How Do Sperm Get to the Egg? Bioengineering Expertise Needed!

In order to provide better diagnosis and treatment of infertility and to develop better contraceptive methods, more needs to be learned about how sperm move through the female reproductive tract. Crucial phases of mammalian sperm transport include passage through the cervix and uterotubal junction, storage in the oviductal sperm storage reservoir, release from the reservoir, and location of the egg. There is some evidence for the existence of special passageways for sperm in the cervix, but this needs to be demonstrated and the mechanism of guiding sperm through the cervix needs to be elucidated. Passage of sperm through the uterotubal junction requires sperm to have certain proteins, but how these proteins function is not known. To release themselves from the oviductal storage reservoir, sperm undergo motility hyperactivation; however, the process is not understood. Finally, chemotactic agents emanating from the vicinity of the egg may modulate sperm flagellar movement; however, little is known about how motility is regulated and how changes in flagellar beat patterns enable sperm to reach the egg. There are three main areas in which bioengineers can provide crucial help for elucidating these mysteries: (1) by developing a method for measuring and comparing sperm flagellar bending patterns, (2) by improving optical methods for envisioning the movement of sperm within the female reproductive tract, and (3) by developing chambers that mimic the physical environment of the tract so that molecular mechanisms that regulate sperm movement can be identified.     

Comparison of INAA and RNAA Methods with Thermal-Ionization Mass Spectrometry for Iridium Determinations in Atmospheric Tracer Studies

The sensitivity and precision of instrumental neutron activation analysis (NAA), radiochemical neutron activation analysis (RNAA), and thermal ionization mass spectrometry (TIMS) are compared for the determination of Ir in ambient size-fractionated aerosol particulate samples. The results of the TIMS analyses indicated high analytical precision (0.2% at >50 pg Ir), but the sensitivity of detection was limited by blank values (300–500 fg). The sensitivities for INAA and RNAA were comparable, i.e., 60 to 90 fg in size-segregated particulate samples.