Influence of correlated errors on the estimation of the relaxation time spectrum in dynamic light scattering

An important step in analyzing data from dynamic light scattering is estimating the relaxation time spectrum from the correlation time function. This estimation is frequently done by regularization methods. To obtain good results with this step, the statistical errors of the correlation time function must be taken into account [J. Phys. A 6, 1897 (1973)]. So far error models assuming independent statistical errors have been used in the estimation. We show that results for the relaxation time spectrum are better if correlation between statistical errors is taken into account. There are two possible ways to obtain the error sizes and their correlations. On the one hand, they can be calculated from the correlation time function by use of a model derived by Sch?tzel. On the other hand, they can be computed directly from the time series of the scattered light. Simulations demonstrate that the best results are obtained with the latter method. This method requires, however, storing the time series of the scattered light during the experiment. Therefore a modified experimental setup is needed. Nevertheless the simulations also show improvement in the resulting relaxation time spectra if the error model of Sch?tzel is used. This improvement is confirmed when a lattice with a bimodal sphere size distribution is applied to experimental data.     

Changes in populations of Listeria monocytogenes in a medium with internal pH control containing Streptococcus cremoris

Behavior of Listeria monocytogenes in a commercial starter culture medium with internal pH control was examined. The IPCM-1 medium was inoculated with L. monocytogenes (strain V7, Scott A, or California) at ca. 10(3) cfu/ml and Streptococcus cremoris (.25%, 1.6 x 10(5) or 1.0%, 8.6 x 10(5) cfu/ml) and was incubated at 21 or 30 degrees C for 30 h. The pH of the uninoculated medium and control (L. monocytogenes only) was between 6.8 and 7.0 before and after incubation. The area on a figure between control and treatment curves for numbers of L. monocytogenes was calculated, designated as area of inhibition, and used to quantitate inhibition of L. monocytogenes caused by S. cremoris. No significant difference was found in area of inhibition or pH values at 6, 24, and 30 h of incubation among the three strains of L. monocytogenes for a given set of conditions (percentage of S. cremoris added and temperature). Inhibition of the pathogen increased with an increase in amount of S. cremoris inoculum used and with higher rather than lower incubation temperature. Populations of L. monocytogenes in IPCM-1 medium without S. cremoris after 30 h of incubation were 10(6) to 10(7)/ml at 21 degrees C and 10(8)/ml at 30 degrees C. At 21 degrees C inhibition of Listeria began after 18 and 24 h and at 30 degrees C after 12 and 15 h of incubation in samples inoculated with 1.0 and .25% S. cremoris, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

ESBL-producing E. coli in Austrian sewage sludge

The aim of this study was to investigate the degree of contamination of sewage sludge with ESBL-producing Escherichia coli strains and the effectiveness of different sewage sludge treatment methods.Monthly sewage sludge samples were collected between January and September 2009 in 5 different sewage treatment plants and tested for the presence of ESBL E. coli. In addition, the number of colony forming units (CFU) of E. coli and coliform bacteria before and after the different sludge treatment methods (aerobic/anaerobic digestion, lime stabilization, and thermal treatment) was investigated.Of the 72 sewage sludge samples investigated, ESBL-positive E. coli were found in 44 (61.1%) sewage sludge samples. The classification of β-lactamase groups was carried out in 15 strains resulting in the detection of 2 different groups (CTX-M and TEM) of bla genes. All 15 of them had a CTX-M gene and 4 of these strains furthermore carried a TEM gene.With regard to the CFU of E. coli and coliform bacteria, thermal treatment and lime stabilization following dehydration sufficiently reduced pathogen concentrations. The plants using merely stabilization and dehydration showed an increase of E. coli and coliform bacteria and thus also an increase in ESBL-producing E. coli.     

Isolation of a gene encoding a developmentally regulated T cell-specific protein with a guanine nucleotide triphosphate-binding motif

In this study, we describe a novel full length cDNA clone designated Tgtp that encodes a predicted 415-amino acid a T cell-specific guanine nucleotide triphosphate-binding protein (TGTP) bearing the characteristic motifs of a guanine nucleotide triphosphate (GTP) binding protein. Tgtp is expressed preferentially, if not exclusively, in T cells, and is up-regulated in both unfractionated and in purified CD4+8+ thymocytes upon TCR cross-linking. In contrast, expression of Tgtp is peripheral T cells is maintained at relatively high levels and is not grossly affected by TCR cross-linking. Antiserum generated against synthetic peptides from the predicted TGTP amino acid sequence recognized a single protein with a molecular mass of approximately 50 kDa, corresponding well with the computed molecular mass of 47 kDa. The only known relative of Tgtp is MUSGTP, which is reportedly expressed in B cells and bears a GTP binding motif. Thus, the discovery of Tgtp resolves a subfamily of molecules with GTP binding motifs and apparent lymphoid lineage-restricted expression. Given the restricted expression pattern in T cells, the up-regulated expression observed in response to TCR signaling in immature thymocytes, and the presence of the motifs characteristic of GTP binding proteins, we suggest that TGTP may have an important function in T cell development and/or T cell activation.     

Cisplatin resistance is associated with reduced interferon-gamma-sensitivity and increased HER-2 expression in cultured ovarian carcinoma cells

In ovarian carcinoma cells, the combination of interferon-gamma (IFN-gamma) and cisplatin (cDDP) has been reported to result in a synergistic amplification of antiproliferative activity. To assess whether IFN-gamma may also prevent the occurrence of cisplatin resistance, the human ovarian carcinoma cell line HTB-77 was treated repeatedly in an intermittent fashion with either cisplatin alone (HTB-77cDDP) or cisplatin plus IFN-gamma (HTB-77cDDP + IFN). After 8 months of treatment, both new lines (HTB-77cDDP or HTB-77cDDP + IFN) were found to be three times more resistant to cisplatin than the wild-type cells (HTB-77wt). IFN-gamma could not prevent the development of cisplatin resistance. Interestingly, both HTB-77cDDP and HTB-77cDDP + IFN cells were also less IFN-gamma sensitive than the parental line. Both cisplatin-resistant lines expressed p185HER-2 and HER-2 mRNA at a higher concentration than the HTB-77wt cells. IFN-gamma was in all three HTB-77 cell lines able to suppress the HER-2 message and its encoded protein. The expression of IFN-gamma-induced antigens, namely CA-125 and class II antigens of the major histocompatibility complex (HLA-DR), was markedly augmented by IFN-gamma in all three lines, whereby the most prominent effect was seen in HTB-77cDDP and HTB-77cDDP + IFN.     

Borrelia burgdorferi: another cause of foodborne illness?

Borrelia burgdorferi was identified as the etiological agent of Lyme disease in 1982. This Gram-negative spirochete is classified in the order Spirochaetales and the family Spirochaetaceae. The pathogen is fastidious, microaerophilic, mesophilic and metabolises glucose through the Embden-Meyerhof pathway. A generation time of 11 to 12 h at 37 degrees C in Barbour-Stoenner-Kelly medium has been reported. Lyme disease, named after Lyme in Connecticut, is distributed globally. It is the most commonly reported vector-borne disease in the United States, where the incidence is highest in the eastern and midwestern states. Since establishment of national surveillance in 1982, there has been a nine-fold increase in the number of cases reported to the U.S. Centers for Disease Control. The deer tick of the genus Ixodes is the primary vector of Lyme borreliosis. The tick may become infected with B. burgdorferi, by feeding on an infected host, at any point in its 2-year life cycle which involves larval, nymphal and adult stages. The infection rate in deer ticks may be as high as 40% in endemic areas. The primary vertebrate reservoirs for Ixodes are the white-footed mouse (Peromyscus leucopus) and the white-tailed deer (Odocopileus virginianus). Dairy cattle and other food animals can be infected with B. burgdorferi and hence some raw foods of animal origin might be contaminated with the pathogen. Recent findings indicate that the pathogen may be transmitted orally to laboratory animals, without an arthropod vector. Thus, the possibility exists that Lyme disease can be a food infection. In humans, the symptoms of Lyme disease, which manifest themselves days to years after the onset of infection, may involve the skin, cardiac, nervous and/or muscular systems, and so misdiagnosis can occur.     

Application of heterogeneous nucleation theory to precipitate nucleation at GP zones

The accelerated nucleation of precipitates at GP zones is explained using heterogeneous nucleation theory. Nucleation at zone : matrix boundaries is encouraged by several factors: 1) the chemical interfacial energy of zone : matrix boundaries can significantly decrease the interfacial energy barrier to nucleation; 2) destruction of quenched-in excess vacancies at incoherent portions of the nucleus surface may make the change in the volume free energy significantly more negative; 3) the crystal structures of the zone and matrix are identical and parallel which permits the nucleus to be faceted in both phases. Some additional assistance to nucleation at GP zones is provided by: 4) the accelerated diffusivity resulting from the presence of excess vacancies and 5) the large area of zone : matrix boundary per unit volume of matrix. These factors can more than compensate for the decreased solute supersaturation due to the formation of GP zones and provide an explanation for the enhanced nucleation of precipitates in the presence of GP zones.     

Traffic analysis and display for the San Francisco Vessel Traffic System

To help improve harbor safety in the face of increasing shipping volume and vessel sites, an experimental Vessel Traffic System has been designed, fabricated, and installed in San Francisco Harbor. The Traffic Analysis and Display portion of the system uses computer generated synthetic map and text displays to provide an interactive system for up to three operators. A series of services has been designed which enable the operators to obtain radar contact information and to enter, modify, and recall text information through a series of simple keyboard actions.

In addition to the interactive working displays, 4 supporting displays have been provided for designated map segments of the harbor, along with two alpha numeric displays for summary text information. A set of symbols has been developed to allow quick recognition of the vessel traffic situation by the operators.

A control computer connected to three interactive display computers and five passive display units provides complete radar contact processing and display, as well as quick response to independent operator requests for information or services. The operators can put vessels into any one of 3 basic categories which allows them to keep the vessels sorted and easily follow the progress of the important ones through the harbor.

A background program supplements the operator actions by looking for and reporting specific trouble situations, such as collision warnings, allowing an operator to concentrate on a particular situation without fear of missing a major problem elsewhere in the harbor.