Solid phase microextraction of stale flavour volatiles from the headspace of UHT milk

Solid phase microextraction (SPME) offers a solvent‐free and less labour‐intensive alternative to traditional flavour isolation techniques. In this instance, SPME was optimised for the extraction of 17 stale flavour volatiles (C3–11,13 methyl ketones and C4–10 saturated aldehydes) from the headspace of full‐cream ultrahigh‐temperature (UHT)‐processed milk. A comparison of relative extraction efficiencies was made using three fibre coatings, three extraction times and three extraction temperatures. Linearity of calibration curves, limits of detection and repeatability (coefficients of variation) were also used in determining the optimum extraction conditions. A 2 cm fibre coating of 50/30 µm divinylbenzene/Carboxen/polydimethylsiloxane in conjunction with a 15 min extraction at 40 °C were chosen as the final optimum conditions. This method can be used as an objective tool for monitoring the flavour quality of UHT milk during storage. Copyright © 2005 Society of Chemical Industry     

Chromatographic studies on fatty acid dinners: Gas-liquid chromatography,high performance liquid chromatography and thin-layer chromatography

A high performance size exclusion Chromatographic method was developed for the separation of monomer, dimer and trimer fatty acids in thermally oxidized or used fats and oils. The system was composed of two styrene/divinylbenzene copolymer columns with toluene as the mobile phase and refractometry as the mode of detection. The internal standardization method was used for quantitation with monostearin as the internal standard. Quantitation of monomer, dimer and trimer content in various samples correlated well with results obtained by GLC analysis and gravimetically by size exclusion chromatography.     

Cyclic fatty acid monomer: Isolation and purification with solid phase extraction

The application of a combined solid phase extraction (SPE)/clean-up procedure to the isolation of a purified fraction containing all the monomeric cyclic fatty acid methyl esters is described. Extraction of the nonpolar lipid components from nonurea-adducting (NUA) filtrates is performed on a reverse phase octadecyl bonded silica minicolumn. Stepwise elution of the SPE-retained materials through silica gel using several solvents allowed the separation of a pure fraction containing the cyclic monomers that can be used for a more reliable quantitative estimation of these compounds in edible fats and oils.     

Characterization of the volatile decomposition products of oxidized methyl arachidonate

The volatile thermal and oxidative decomposition products of methyl arachidonate were separated by capillary gas chromatography and identified by mass spectrometry. Various aldehydes, ketones, aldehyde esters, hydrocarbons and alcohols were identified. The major products included hexanal, methyl 5-oxopentanoate, pentane, methyl butanoate and 2,4-decadienal, which could be important to off-odor development in oxidized food systems containing arachidonate.     

Scalability study of the ad hoc on‐demand distance vector routing protocol

As mobile networking continues to experience increasing popularity, the need to connect large numbers of wireless devices will become more prevalent. Many recent proposals for ad hoc routing have certain characteristics that may limit their scalability to large networks. This paper examines five different combinations of modifications that may be incorporated into virtually any on‐demand protocol in order to improve its scalability. The scalability of current on‐demand routing protocols is evaluated through the selection of a representative from this class of protocols. The performance of the un‐modified on‐demand protocol is compared against that of it combined with each of the scalability modifications. Each scheme's behavior is analyzed in networks as large as 10,000 nodes through detailed simulation. Based on the observations, conclusions are drawn as to the expected scalability improvement that can be achieved by each modification. Copyright © 2003 John Wiley & Sons, Ltd.     

System-level reliability assessment of mixed-signal convergent microsystems

The next-generation convergent microsystems, based on system-on-package (SOP) technology, require up-front system-level design-for-reliability approaches and appropriate reliability assessment methodologies to guarantee the reliability of digital, optical, and radio frequency (RF) functions, as well as their interfaces. Systems approach to reliability requires the development of: i) physics-based reliability models for various failure mechanisms associated with digital, optical, and RF Functions, and their interfaces in the system; ii) design optimization models for the selection of suitable materials and processing conditions for reliability, as well as functionality; and iii) system-level reliability models understanding the component and functional interaction. This paper presents the reliability assessment of digital, optical, and RF functions in SOP-based microsystems. Upfront physics-based design-for-reliability models for various functional failure mechanisms are presented to evaluate various design options and material selection even before the prototypes are made. Advanced modeling methodologies and algorithms to accommodate material length scale effects due to enhanced system integration and miniaturization are presented. System-level mixed-signal reliability is discussed thorough system-level reliability metrics relating component-level failure mechanisms to system-level signal integrity, as well as statistical aspects.     

Detection of terminal deoxynucleotidyl transferase (TdT) in nonhematopoietic small round cell tumors of children

In the differential diagnosis of small round cell tumors (SRCTs), terminal deoxynucleotidyl transferase (TdT) is often used as a marker for lymphoblastic lymphomas and leukemias. However, the specificity of TdT using the avidin-biotin-immunoperoxidase (ABC) method is not well documented. To address this issue, we stained paraffin-embedded biopsy specimens of 64 cases of childhood SRCTs using the ABC method with anti-TdT. For any TdT-positive tumors, an additional antibody panel for lymphoid markers was applied. Two patterns of TdT positivity were observed: (1) tumor specific, consisting of strong to moderate nuclear staining, and (2) scattered positive lymphoid cells, usually in a perivascular location and expressing T-cell markers. Analysis showed that 7 of 10 medulloblastomas stained with TdT in a tumor-specific pattern (4 cases moderately to strongly positive in 75-100% of tumor cells, 3 cases weakly to moderately positive in 25-50% of cells). Also, 1 of 19 rhabdomyosarcomas and 1 of 8 Ewing's sarcomas showed moderate to strong tumor-specific TdT staining in 100 and 10% of cells, respectively. Scattered TdT-positive lymphoid cells were observed in 27% of these 64 SRCTs. These findings emphasize that TdT positivity should not be relied upon exclusively for making a diagnosis of lymphoblastic leukemia or lymphoma or ruling out other SRCTs.     

The return to smoking: 1-year relapse trajectories among female smokers.

Research has demonstrated that a lapse in cigarette abstinence often leads smokers to fully relapse (i.e., return to daily smoking). However, patterns of smoking resumption beyond the point at which relapse occurs have not been examined in systematic follow-up studies. Daily cigarette intake data for 108 female adult smokers who participated in a smoking cessation trial were recorded at several points during the 365 days following the participants' quit date. SAS Proc Traj, a group-based mixture modeling procedure, was used to determine cigarette-use trajectories over time (i.e., patterns of smoking resumption). Over the 365 days, 27% of the sample maintained abstinence. Among the 73% who relapsed, four distinct trajectories emerged: low-level users (8% of the overall sample), moderate users (17%), slow-returners (15%), and quick-returners (33%). A few individual characteristics differentiated these groups. Overall, the findings illustrate that, after relapsing, smokers do not follow a unitary course of smoking resumption; rather, they exhibit more variable resumption patterns than previously assumed.     

SEK1 deficiency reveals mitogen-activated protein kinase cascade crossregulation and leads to abnormal hepatogenesis

SEK1 (MKK4/JNKK) is a mitogen-activated protein kinase activator that has been shown to participate in vitro in two stress-activated cascades terminating with the SAPK and p38 kinases. To define the role of SEK1 in vivo, we studied stress-induced signaling in SEK1(-/-) embryonic stem and fibroblast cells and evaluated the phenotype of SEK1(-/-) mouse embryos during development. Studies of SEK1(-/-) embryonic stem cells demonstrated defects in stimulated SAPK phosphorylation but not in the phosphorylation of p38 kinase. In contrast, SEK1(-/-) fibroblasts exhibited defects in both SAPK and p38 phosphorylation, demonstrating that crosstalk exists between the stress-activated cascades. Tumor necrosis factor alpha and interleukin 1 stimulation of both stress-activated cascades are severely affected in the SEK1(-/-) fibroblast cells. SEK1 deficiency leads to embryonic lethality after embryonic day 12.5 and is associated with abnormal liver development. This phenotype is similar to c-jun null mouse embryos and suggests that SEK1 is required for phosphorylation and activation of c-jun during the organo-genesis of the liver.