Measurement of the tt production cross section in pp collisions at square root of s = 1.96 TeV

We present a measurement of the top quark pair production cross section in pp collisions at square root of s = 1.96 TeV using 318 pb(-1) of data collected with the Collider Detector at Fermilab. We select tt[over ] decays into the final states enu+jets and mu nu+ jets, in which at least one b quark from the t-quark decays is identified using a secondary vertex-finding algorithm. Assuming a top quark mass of 178 GeV/c2, we measure a cross section of 8.7 +/- 0.9(stat)(-0.9)+1.1(syst) pb. We also report the first observation of tt[over ] with significance greater than 5sigma in the subsample in which both b quarks are identified, corresponding to a cross section of 10.1(-1.4)+1.6(stat)(-1.3)+2.0(syst) pb.     

Search for a neutral Higgs boson decaying to a W boson pair in pp collisions at square root of s = 1.96 TeV

We present the results of a search for standard model Higgs boson production with decay to WW*, identified through the leptonic final states e+ e- nu nu,+/-mu -/+nu nu and mu+ mu- nu nu. This search uses 360 pb -1 of data collected from pp collisions at square root of s =1.96 TeV by the upgraded Collider Detector at Fermilab (CDF II). We observe no signal excess and set 95% confidence level upper limits on the production cross section times branching ratio for the Higgs boson to WW* or any new scalar particle with similar decay products. These upper limits range from 5.5 to 3.2 pb for Higgs boson masses between 120 and 200 GeV/c2.     

Hydrophobic self-assembly of a perylenediimide-linked DNA dumbbell into supramolecular polymers

The self-assembly of DNA dumbbell conjugates possessing hydrophobic perylenediimide (PDI) linkers separated by an eight-base pair A-tract has been investigated. Cryo-TEM images obtained from dilute solutions of the dumbbell in aqueous buffer containing 100 mM NaCl show the presence of structures corresponding to linear end-to-end assemblies of 10-30 dumbbell monomers. The formation of assemblies of this size is consistent with analysis of the UV-vis and fluorescence spectra of these solutions for the content of PDI monomer and dimer chromophores. Assembly size is dependent upon the concentration of dumbbell and salt as well as the temperature. Kinetic analysis of the assembly process by means of salt-jump stopped-flow measurements shows that it occurs by a salt-triggered isodesmic mechanism in which the rate constants for association and dissociation in 100 mM NaCl are 3.2 × 10(7) M(-1)s(-1) and 1.0 s(-1), respectively, faster than the typical rate constants for DNA hybridization. TEM and AFM images of samples deposited from solutions having higher concentrations of dumbbell and NaCl display branched assemblies with linear regions >1 μm in length and diameters indicative of the formation of small bundles of dumbbell end-to-end assemblies. These observations provide the first example of the use of hydrophobic association for the assembly of small DNA duplex conjugates into supramolecular polymers and larger branched aggregates.     

A disposable microfluidic cassette for DNA amplification and detection

A pneumatically driven, disposable, microfluidic cassette comprised of a polymerase chain reaction (PCR) thermal cycler, an incubation chamber to label PCR amplicons with up-converting phosphor (UPT) reporter particles, conduits, temperature-activated, normally closed hydrogel valves, and a lateral flow strip, was constructed and tested. The hydrogel valves, which were opened and closed with the aid of electrically controlled thermoelectric units, provided a simple means to seal the PCR reactor and suppress bubble formation. The hydrogel-based flow control was electronically addressable, leakage-free, and biocompatible. To test the device, a solution laden with genomic DNA isolated from B. cereus was introduced into the microfluidic cassette and a specific 305 bp fragment was amplified. The PCR amplicons were labelled with the phosphor (UPT) reporter particles, applied to the lateral flow strip, bound to pre-immobilized ligands, and detected with an IR laser that scanned the lateral flow strip and excited the phosphor (UPT) particles that, in turn, emitted light in the visible spectrum. The UPT particles do not bleach, they provide a permanent record, and they readily facilitate the filtering of background noise. The cassette described herein will be used for rapid testing at the point of care.     

Reduction of the allylic substituents in Ni(I)(1,8-dipropenyl-1,4,8,11-tetraazacyclotetradecane)+ by the central Ni(I) in aqueous solutions

The complex Ni(II)(1,8,-di-2-propenyl-1,4,8,11-tetraazacyclotetradecane)(2+), (NiL(1))(2+), was synthesized. X-ray crystallography demonstrates that the complex obtained is the trans-III isomer. The allylic substituents shift the redox couples (NiL(1))(3+/2+) and (NiL(1))(2+/+) anodically relative to the corresponding couples for Ni(II)(1,4,8,11-tetraazacyclotetradecane)(2+), (NiL(2))(2+), as expected. Surprisingly, the lifetime of (NiL(1))(+) in neutral aqueous solutions is shorter than that of (NiL(2))(+). Pulse radiolysis experiments reveal that the allylic substituents are reduced by the central Ni(I) ion. The first step in this reduction is a general acid catalyzed process. The results suggest that this step involves schematically the reaction Ni(I)[bond]NCH(2)CH[double bond]CH(2)(+) + H(+) --> Ni(III)[bond]NCH2CH2CH(2)(2+). The latter transient decomposes slowly with a half-life time of several minutes. Preliminary results support the suggestion that (NiL(2))(+), or other Ni(I)L complexes of this family, might reduce many alkenes present in the solution.     

Reduction of pyracylene by alkali metals: Mechanism and formation of aggregates

Five reaction stages have been identified in the reduction of pyracylene to its dianion. The same stages were also observed in the photochemical oxidation starting with the dianion. The formation of dimers of anions and of mixed valence aggregates is discussed.     

The contribution of the accreditation process to public administration: promotion of vital organizational changes

Accumulative evidence suggests that the implementation of international standard operating procedures, induce, by their virtues, major organizational changes. These changes are both cultural and behavioral including changes in decision-making processes, organizational norms, and values. The decision of any organization to adopt quality assurance, specifically via accreditation, should be regarded as a strategic one. As such, it prerequisites top management commitment, budgeting the process and promoting active inter-collaboration of all organizational members. The accreditation process according to ISO/IEC 17025:1999 of the Haifa Public Health Laboratory, will be used as a case study. A number of practical benefits of such organizational changes will be demonstrated and discussed, among them improved quality customer service and handling customer's complaints, establishing multichannel communication, enhanced interlaboratory collaboration and coordination. It is important to note that the accreditation process was accompaniment by extensive training of both management and employees on-site and off-site.     

Light Irradiation of Mouse Spermatozoa: Stimulation of In Vitro Fertilization and Calcium Signals

Irradiation of mouse spermatozoa by 630 nm He-Ne laser was found to enhance the intracellular calcium levels and fertilizing potential of these cells. The effect of light on calcium transport and on fertilization rate was abrogated in the absence of Ca²⁺during the irradiation time, indicating that the effect of light is Ca²⁺dependent. The stimulatory effect of light on Ca²⁺uptake was abolished in the presence of a voltage-dependent Ca²⁺-channel inhibitor nifedipine, indicating the involvement of a plasma membrane voltage-dependent Ca²⁺channel. Furthermore, the stimulatory effect of light was completely inhibited by the mitochondrial uncoupler FCCP, indicating that laser irradiation might affect the mitochondrial Ca²⁺transport mechanisms. A causal association between laser irradiation, reactive oxygen species (ROS) generation and sperm function was indicated by studies with ROS scavengers, superoxide dismutase (SOD) and catalase, and exogenous hydrogen peroxide. The SOD treatment, which enhanced H₂O₂ production, resulted in increased Ca²⁺uptake and enhanced fertilization rate. On the other hand, catalase, which decomposes H₂O₂, impaired the light-induced stimulation in Ca²⁺uptake and the fertilization rate. Taken together, the data suggest that H₂O₂ might be involved in the irradiation effects, and indeed laser irradiation enhances the production of H₂O₂, by spermatozoa. These results indicate that the effect of 630 nm He-Ne laser irradiation is mediated through the generation of H₂O₂ by the spermatozoa and that this effect plays a significant role in the augmentation of the sperm cells' capability to fertilize metaphase H-arrested eggs in vitro.     

Electron spin polarization of functionalized fullerenes. Reversed quartet mechanism

Time-resolved electron paramagnetic resonance (TREPR) spectroscopy was used to study two functionalized fullerenes consisting of a C60 moiety covalently linked to TEMPO radical via spacers of different length. Photoinduced electron spin polarization (ESP) reflecting a non-Boltzmann population within the energy levels of the spin system was observed in the electronic ground and excited states. Both fullerenes are characterized by a sign inversion of their TREPR spectra. A new mechanism of ESP generation was suggested to explain the experimental results. This mechanism, termed as the reversed quartet mechanism (RQM), includes the intersystem crossing process, which generates ESP in the excited trip-doublet and trip-quartet (2T1 and 4T1) states. This ISC is accompanied by ESP transfer to the ground state (2S0) by either electron-transfer reaction (in our case via charge transfer state, 2CT, i.e., 2T1--> 2CT --> 2S0 or internal conversion, 2T1--> 2S0.