The bar spectral sequence converging toh *(SO(2n+1))

We study the bar spectral sequence converging toh _*(SO(2n+1)), whereh is an algebra theory overBP. The differentials are determined completely ifh=P(l) andn<2 ^l . These results will be used in a future paper on the MoravaK-theories ofSO(2n+1), with no restriction onn. As another application, we determineBP _*(Spin(7)) including much of its algebra structure.AMS Subject Classification: 57T10, 57T30, 55N22     

Berechnung des Wirkungsquerschnitts der direkten Paarerzeugung bei Streuung von 5,511 MeV- und 32 MeV-Elektronen an einem statischen Coulombfeld

Differential cross sections for direct pair production by electrons with total energiesE ₀=5.511 and 32 MeV in copper are calculated in lowest order of pertubation theory and Born approximation, including the matrix elements of the electron exchange effect. Integration over particle angles and — in the case ofE ₀=32 MeV — over the energy of one outgoing electron was performed numerically on an IBM 7044 computer by using Gaussian quadrature formulas in FORTRAN-programs. The results forE ₀=5.511 MeV show a severe reduction of the differential cross section due to the exchange effect, while the results for 32 MeV are in fairly good agreement with the pair production experiment performed byCriegee in 1959.     

Validation of three rapid screening methods for detection of verotoxin-producing Escherichia coli in foods: interlaboratory study

An interlaboratory study was conducted for the validation of 3 methods for the detection of all verotoxin-producing Escherichia coli (VTEC) in foods. The methods were a multi-analyte 1-step lateral flow immunoassay (LFIA) for detection of E. coli O157 and verotoxin (VT); an enzyme-linked immunosorbent assay targeted against VT1, VT2, and VT2c (VT-ELISA); and a polymerase chain reaction (PCR) method for detection of VT genes (VT-PCR). Aliquots (25 g or 25 mL) of 4 food types (raw minced [ground] beef, unpasteurized milk, unpasteurized apple juice [cider], and salami) were individually inoculated with low numbers (<9 to 375 cells/25 g) of 6 test strains of E. coli (serogroups O26, O103, O111, O145, and O157) with differing VT-producing capabilities. Five replicates for each test strain and 5 uninoculated samples were prepared for each food type. Fourteen participating laboratories analyzed samples using the LFIA, 9 analyzed the samples by ELISA, and 9 by PCR. The LFIA for O157 and VT had a specificity (correct identification of negative samples) of 92 and 94%, respectively, and a sensitivity (correct identification of positive samples) of 94 and 55%, respectively. The VT-ELISA and VT-PCR had a specificity of 98 and 99%, respectively, and a sensitivity of 89 and 72%, respectively.     

Temporal Control of Gelation and Polymerization Fronts Driven by an Autocatalytic Enzyme Reaction

Chemical systems that remain kinetically dormant until activated have numerous applications in materials science. Herein we present a method for the control of gelation that exploits an inbuilt switch: the increase in pH after an induction period in the urease‐catalyzed hydrolysis of urea was used to trigger the base‐catalyzed Michael addition of a water‐soluble trithiol to a polyethylene glycol diacrylate. The time to gelation (minutes to hours) was either preset through the initial concentrations or the reaction was initiated locally by a base, thus resulting in polymerization fronts that converted the mixture from a liquid into a gel (ca. 0.1 mm min^?1). The rate of hydrolytic degradation of the hydrogel depended on the initial concentrations, thus resulting in a gel lifetime of hours to months. In this way, temporal programming of gelation was possible under mild conditions by using the output of an autocatalytic enzyme reaction to drive both the polymerization and subsequent degradation of a hydrogel.     

Synthesis of 2-substituted oxazoloquinazolinones

Chemistry of Heterocyclic Compounds - The reaction of methyl 2-isothiocyanatobenzoate and 1-azido-3-(4-substituted phenyl)propan-2-ones in the presence of triphenyl phosphine in dioxane by heating...     

Application of 2,6-diazidopurine derivatives in the synthesis of thiopurine nucleosides

2,6-Diazidopurine derivatives undergo double azide–alkyne 1,3-dipolar cycloaddition (CuAAC) reactions to give 2,6-bis-(triazolyl)purine analogs, which undergo selective nucleophilic aromatic substitution with various thiols at C(6). This synthetic sequence produces nucleoside analogs with 6-alkyl/arylthio-2-(4-alkyl/aryl-1H-1,2,3-triazol-1-yl)purine bases. In contrast, glycosylated 2,6-diazidopurines exhibit reasonable C(2) selectivity in nucleophilic aromatic substitution with thiols. This permits the synthesis of 2-alkylthio-6-azido-purine derivatives, which after CuAAC provide the corresponding 2-alkylthio-6-triazolyl-purine analogs. The latter are also susceptible to nucleophilic aromatic substitution with amines at C(6). The above mentioned compounds are useful molecular platforms in terms of medicinal chemistry.