Machine setup and component placement in printed circuit board assembly

Populating printed circuit boards is one of the most costly and time-consuming steps in electronics assembly. At the beginning of each work order, three decisions are required: (1) a sequence must be specified for placing the individual components on the board; (2) tape reels must be assigned to positions on the magazine rack; and (3) a retrieval plan must be determined should the same component type be assigned to more than one magazine slot. Collectively, these problems can be modeled as a nonlinear integer program. In this paper, we develop a series of algorithms for solving each using an iterative two step approach. Initially, a placement sequence is generated with a weighted, nearest neighbor traveling salesman problem (TSP) heuristic; the two remaining problems are then formulated as a quadratic integer program and solved with a Lagrangian relaxation scheme. As a final step, the current magazine assignments are used to update the placement sequence, and the entire process is repeated. Our ability to deal, at least in part, with simultaneous machine operations represents the major contribution of this work. The methodology was simulated for a set of boards obtained from Texas Instruments and theoretically compared with a heuristic currently in use.     

Flow cytometry: an alternative method for direct quantification of antigens adsorbed to aluminum hydroxide adjuvant

Flow cytometry (FC) has been widely used in biological research; however, its use for vaccine characterization has been very limited. Here we describe the development of an FC method for the direct quantification of two Neisseria meningitidis vaccine antigens, in mono- and multivalent formulations, while still adsorbed on aluminum hydroxide (AH) suspension. The antibody-based method is specific and sensitive. Because FC allows microscopic particle examination, the entire aluminum suspension carrying adsorbed antigen(s) can be analyzed directly. In addition to determining antigen concentration and identity, the assay is able to determine the distribution of the antigens on AH. High correlation coefficients (r²) were routinely achieved for a broad range of antigen doses from 0 to 150 μg/dose. Traditional assays for quantitative and qualitative antigen characterization on AH particles involve either complete aluminum dissolution or antigen desorption from the adjuvant. Because our direct method uses the whole AH suspension, the cumbersome steps used by traditional methods are not required. Those steps are often inefficient in desorbing the antigens and in some cases can lead to protein denaturation. We believe that this novel FC-based assay could circumvent some of the complex and tedious antigen–adjuvant desorption methods.     

miR-126&126* Restored Expressions Play a Tumor Suppressor Role by Directly Regulating ADAM9 and MMP7 in Melanoma

The abnormal expression of several microRNAs has a causal role in tumorigenesis with either antineoplastic or oncogenic functions. Here we demonstrated that miR-126 and miR-126* play a tumor suppressor role in human melanoma through the direct or indirect repression of several key oncogenic molecules. The expression levels of miR-126&126* were elevated in normal melanocytes and primary melanoma cell lines, whereas they markedly declined in metastatic cells. Indeed, the restored expression of miR-126&126* in two advanced melanoma cell lines was accompanied by a significant reduction of proliferation, invasion and chemotaxis in vitro as well as of growth and dissemination in vivo. In accordance, the reverse functional effects were obtained by knocking down miR-126&126* by transfecting antisense LNA oligonucleotides in melanoma cells. Looking for the effectors of these antineoplastic functions, we identified ADAM9 and MMP7, two metalloproteases playing a pivotal role in melanoma progression, as direct targets of miR-126&126*. In addition, as ADAM9 and MMP7 share a role in the proteolytic cleavage of the HB-EGF precursor, we looked for the effectiveness of this regulatory pathway in melanoma, confirming the decrease of HB-EGF activation as a consequence of miR-126&126*-dependent downmodulation of ADAM9 and MMP7. Finally, gene profile analyses showed that miR-126&126* reexpression was sufficient to inactivate other key signaling pathways involved in the oncogenic transformation, as PI3K/AKT and MAPK, and to restore melanogenesis, as indicated by KIT/MITF/TYR induction. In view of this miR-126&126* wide-ranging action, we believe that the replacement of these microRNAs might be considered a promising therapeutic approach.     

Correlates of dental visits among community‐residing Latino elders: a public health alert

doi:10.1111/j.1741‐2358.2009.00335.x
Correlates of dental visits among community‐residing Latino elders: a public health alert Objectives: To examine oral service utilisation in a probability sample of community‐residing Latino elders. Background: Older Latinos are at a potential increased risk of oral diseases, given their higher prevalence of co‐morbidities and lower rate of dental service utilisation. Methods: A prevalence survey was conducted among a random sample of Latino (largely Puerto Rican) elders (n = 205; mean age = 75.8; SD ± 5.3) in New York City during 2001–2002. A systematic random sample was drawn from the Centers for Medicare and Medicaid Services Beneficiary tape files. Current use of oral health services and self‐reported health conditions was obtained. Functional and cognitive impairment were assessed. Results: Less than half of the sample reported a dental visit in the previous year. The average time since the last dental visit was 54 months (SD ± 84.5). Last year dental visit compliers were more likely to be unmarried, living alone, with higher levels of education, fewer health conditions and less impairment with activities of daily living. In multivariate analyses, problem‐oriented behaviour, Medicaid beneficiary, education, living alone, chronic health conditions and mobility impairment explained 14% of the ‘time since last dental visit’ variance. Conclusions: Given that socio‐demographic and level of functioning determinants appear to influence the frequency of dental visits, a multilevel approach to oral health promotion is imperative.     

Cutting edge: NLRC5-dependent activation of the inflammasome

The nucleotide-binding domain leucine-rich repeat-containing proteins, NLRs, are intracellular sensors of pathogen-associated molecular patterns and damage-associated molecular patterns. A subgroup of NLRs can form inflammasome complexes, which facilitate the maturation of procaspase 1 to caspase 1, leading to IL-1β and IL-18 cleavage and secretion. NLRC5 is predominantly expressed in hematopoietic cells and has not been studied for inflammasome function. RNA interference-mediated knockdown of NLRC5 nearly eliminated caspase 1, IL-1β, and IL-18 processing in response to bacterial infection, pathogen-associated molecular patterns, and damage-associated molecular patterns. This was confirmed in primary human monocytic cells. NLRC5, together with procaspase 1, pro-IL-1β, and the inflammasome adaptor ASC, reconstituted inflammasome activity that showed cooperativity with NLRP3. The range of pathogens that activate NLRC5 inflammasome overlaps with those that activate NLRP3. Furthermore, NLRC5 biochemically associates with NLRP3 in a nucleotide-binding domain-dependent but leucine-rich repeat-inhibitory fashion. These results invoke a model in which NLRC5 interacts with NLRP3 to cooperatively activate the inflammasome.     

Mycophenolic acid differentially impacts B cell function depending on the stage of differentiation

Production of pathogenic Abs contributes to disease progression in many autoimmune disorders. The immunosuppressant agent mycophenolic acid (MPA) has shown clinical efficacy for patients with autoimmunity. The goal of these studies was to elucidate the mechanisms of action of MPA on B cells isolated from healthy individuals and autoimmune patients. In this study, we show that MPA significantly inhibited both proliferation and differentiation of primary human B cells stimulated under various conditions. Importantly, MPA did not globally suppress B cell responsiveness or simply induce cell death, but rather selectively inhibited early activation events and arrested cells in the G0/G1 phase of the cell cycle. Furthermore, MPA blocked expansion of both naive and memory B cells and prevented plasma cell (PC) differentiation and Ab production from healthy controls and individuals with rheumatoid arthritis. Finally, whereas MPA potently suppressed Ig secretion from activated primary B cells, terminally differentiated PCs were not susceptible to inhibition by MPA. The target of MPA, IMPDH2, was found to be downregulated in PCs, likely explaining the resistance of these cells to MPA. These results suggest that MPA provides benefit in settings of autoimmunity by directly preventing activation and PC differentiation of B cells; however, MPA is unlikely to impact autoantibody production by preexisting, long-lived PCs.     

Selection with a peptide fusion inhibitor corresponding to the first heptad repeat of HIV-1 gp41 identifies two genetic pathways conferring cross-resistance to peptide fusion inhibitors corresponding to the first and second heptad repeats (HR1 and HR2) of gp41

We generated four HIV-1 cultures that are resistant to a peptide fusion inhibitor corresponding to the first heptad repeat of gp41 in order to study mechanisms of resistance and gain insights into envelope glycoprotein-mediated membrane fusion. Two genetic pathways emerged that were defined by acquisition of a specific mutation in either the first or second heptad repeat region of gp41 (HR1 or the HR2, respectively). Each pathway was enriched in mutations that clustered in either HR2 and V3 or in HR1 and residues in or near CD4 contact sites. The gp41 mutations in both pathways not only accounted for resistance to the selecting HR1 peptide but also conferred cross-resistance to HR2 peptide fusion inhibitors and enhanced the stability of the six-helix bundle formed by the self-assembly of HR1 and HR2. The gp120 mutations alone enhanced fusion but did not appear to directly contribute to resistance. The implications of these findings for resistance mechanisms and regulation of envelope-mediated fusion are discussed.