Grafting vinyl monomers into nylon-6. II. Graft copolymerization of methyl methacrylate onto nylon-6 by hexavalent chromium ion

The feasibility of chromium(VI) to induce graft copolymerization of methyl methacrylate onto nylon-6 was investigated in the presence of nitrogen. The rate of grafting was determined by varying monomer concentration, chromium(VI) concentration, temperature, acidity of the medium, solvents, inorganic salts, and redox system. The graft yield increases significantly by increasing the monomer concentration. The graft yield increases with increase of [Cr(VI)] up to 0.025 mole/liter. With further increase of [Cr(VI)], the graft yield decreases. The increase of acid concentration up to 0.395 mole/liter results the increase in graft yield. Beyond this concentration the graft yield decreases. The graft yield increases with increase in temperature up to 55°C and thereafter it decreases. The graft yield is medium dependent. The graft yield increases with increasing thiourea concentration upto 0.0025 mole/liter but beyond this concentration, the percentage graft yield decreases. A suitable kinetic scheme has been proposed and the rate equation has been evaluated.     

The effect of carbon black concentration on the dynamic mechanical properties of bromobutyl rubber

The effect of carbon black concentration on the dynamic mechanical properties of bromobutyl rubber vulcanizates has been studied over a wide range of temperature (– 150 to + 250 °C), frequency (3.5 to 110 Hz) and dynamic strain amplitude (0.07 to 5%). The influence of carbon black concentration on the glass-rubber transition has also been investigated with respect to the isochronal variation in dynamic properties. The influence of carbon black concentration consists mainly of the change in the levels of the moduli values in the glassy and rubbery state. In the glassy region; the increase in stiffness with carbon black loading may be fully explained by the hydrodynamic effect of the carbon black particles embedded in the polymer continuum. With increased carbon black concentration the glass-rubber transition temperature (tan peak temperature) does not show a shift in its location but peak shoulder broadening and decrease in peak height are observed. At a particular temperature, the effect of carbon black concentration on dynamic properties of bromobutyl rubber is dependent on the combined effects of applied strain amplitude and frequency. With increase in filler concentration the thermal stability of the vulcanizate increases.     

Reversible inactivation of purified leukocyte integrin CR3 (CD11b/CD18, alpha m beta 2) by removal of divalent cations from a cryptic site

Integrins exhibit reversible changes in their ability to bind ligands and these changes enable transient cell adhesion. We recently showed that leukocyte integrin CR3 (complement receptor type three, CD11b/CD18, alpha m beta 2) may be purified in a form that is either capable or incapable of binding soluble, monomeric ligand and that "inactive" CR3 may be rendered capable of binding ligand by addition of an anti-CR3 mAb known as KIM-127 (Cai and Wright, JBC. 270: 14358, 1995). Here, we demonstrate that active CR3 may be rendered inactive by treatment of immobilized receptor with EDTA. EDTA-treated CR3 failed to bind ligand even in the presence of mM Ca2+ and Mg2+, suggesting that EDTA-treatment caused a change in the receptor that is not readily reversed. EDTA-treated receptor did, however, bind ligand upon addition of KIM-127 plus Mg2+ with an affinity (17.8 +/- 4.5 nM) similar to untreated, active receptor (12.5 +/- 4.7 nM). EDTA-treated CR3 thus exhibits the properties of inactive CR3, in which the ligand binding site is cryptic but subject to exposure by KIM-127. A candidate for the cryptic ligand binding site is the I-domain, a Mg2+-binding region in the alpha chain of CR3. We found that monomeric C3bi binds directly to recombinant I-domain in a Mg(2+)-dependent fashion with an affinity of 300 +/- 113 nM. These results thus suggest that CR3 may be inactivated by removing tightly bound divalent cation from a cryptic site in CR3.     

In vitro processing of herpes simplex virus type 1 DNA replication intermediates by the viral alkaline nuclease, UL12

Herpes simplex virus type 1 (HSV-1) DNA replication intermediates exist in a complex nonlinear structure that does not migrate into a pulsed-field gel. Genetic evidence suggests that the product of the UL12 gene, termed alkaline nuclease, plays a role in processing replication intermediates (R. Martinez, R. T. Sarisky, P. C. Weber, and S. K. Weller, J. Virol. 70:2075-2085, 1996). In this study we have tested the hypothesis that alkaline nuclease acts as a structure-specific resolvase. Cruciform structures generated with oligonucleotides were treated with purified alkaline nuclease; however, instead of being resolved into linear duplexes as would be expected of a resolvase activity, the artificial cruciforms were degraded. DNA replication intermediates were isolated from the well of a pulsed-field gel ("well DNA") and treated with purified HSV-1 alkaline nuclease. Although alkaline nuclease can degrade virion DNA to completion, digestion of well DNA results in a smaller-than-unit-length product that migrates as a heterogeneous smear; this product is resistant to further digestion by alkaline nuclease. The smaller-than-unit-length products are representative of the entire HSV genome, indicating that alkaline nuclease is not inhibited at specific sequences. To further probe the structure of replicating DNA, well DNA was treated with various known nucleases; our results indicate that replicating DNA apparently contains no accessible double-stranded ends but does contain nicks and gaps. Our data suggest that UL12 functions at nicks and gaps in replicating DNA to correctly repair or process the replicating genome into a form suitable for encapsidation.     

NK cells can recognize different forms of class I MHC

NK recognition and lysis of targets are mediated by activation receptor(s) whose effects may be over-ridden by inhibitory receptors recognizing class I MHC on the target. Incubation of normal lymphoblasts with a peptide that can bind to their class I MHC renders them sensitive to lysis by syngeneic NK cells. By binding to class I MHC, the peptide alters or masks the target structure recognized by an inhibitory NK receptor(s). This target structure is most likely an "empty" dimer of class I heavy chain and beta2m as opposed to a "full" class I trimer formed by binding of specific peptide that is recognized by CTL.     

Primary structure of gene H of cattle plague virus strain K]

The paper analyzes the standard legal and methodological assurance of the quality and safety of animal food raw materials and foodstuffs (meat, meat products, fish, shellfish, crayfish and their processing products) by the parasitic purity rates according the requirements under the Russian Federation's laws "On Sanitary and Epidemiological Well-Being of the Population", "On Protection of Consumer's Rights", "On Certification of Products and Services", those of SanPiN, such as 2.3.2.560-96 "Sanitary Requirements for the Quality and Safety of Food Raw Materials and Foodstuffs" and 3.2.569-96 "Prevention of Parasitic Diseases in the Russian Federation".     

Trace Analysis of Zn(II), Be(II), and Bi(III) by Enzyme-Catalyzed Chemiluminescence

A novel technique for the trace analysis of metal ions Zn(II), Be(II), and Bi(III) in bulk solutions is discussed. This technique involves the generation of a chemiluminescence signal from alkaline phosphatase catalyzed hydrolysis of a phosphate derivative of 1,2-dioxetane. Zn(II) can be determined by two methods, reactivation of the alkaline phosphatase apoenzyme and inhibition of the native enzyme. Be(II) and Bi(III) can be determined quantitatively by inhibition of the native enzyme. Subppb to ppm level detection of Zn(II), Be(II), and Bi(III) has been achieved. Initial studies with mixed metals are also reported. The technique described is rapid and sensitive and can be readily applied to the microassay of heavy metal ions.     

An improved load-balancing mechanism based on deadline failure recovery on GridSim

Grid computing has emerged a new field, distinguished from conventional distributed computing. It focuses on large-scale resource sharing, innovative applications and in some cases, high performance orientation. The Grid serves as a comprehensive and complete system for organizations by which the maximum utilization of resources is achieved. The load balancing is a process which involves the resource management and an effective load distribution among the resources. Therefore, it is considered to be very important in Grid systems. For a Grid, a dynamic, distributed load balancing scheme provides deadline control for tasks. Due to the condition of deadline failure, developing, deploying, and executing long running applications over the grid remains a challenge. So, deadline failure recovery is an essential factor for Grid computing. In this paper, we propose a dynamic distributed load-balancing technique called “Enhanced GridSim with Load balancing based on Deadline Failure Recovery” (EGDFR) for computational Grids with heterogeneous resources. The proposed algorithm EGDFR is an improved version of the existing EGDC in which we perform load balancing by providing a scheduling system which includes the mechanism of recovery from deadline failure of the Gridlets. Extensive simulation experiments are conducted to quantify the performance of the proposed load-balancing strategy on the GridSim platform. Experiments have shown that the proposed system can considerably improve Grid performance in terms of total execution time, percentage gain in execution time, average response time, resubmitted time and throughput. The proposed load-balancing technique gives 7 % better performance than EGDC in case of constant number of resources, whereas in case of constant number of Gridlets, it gives 11 % better performance than EGDC.     

Obtaining a durable power of attorney for health care from nursing home residents

BACKGROUND: A durable power of attorney for health care (DPA) allows a person to appoint a surrogate decision-maker for any future period of mental incapacity. The absence of advance directives can lead to confusion and the expenditure of resources while trying to exert a substituted judgment. METHODS: The Wisconsin DPA was presented with an organized pilot program to 150 residents who had been judged by their social workers to have the capacity to make informed decisions regarding medical care. The reasons residents gave for accepting or rejecting a DPA were analyzed. RESULTS: Seventy-nine percent prepared a DPA. Reasons for signing included allowing the resident to decide who would make medical decisions and assuring that specific wishes would be carried out. Twenty-one percent did not execute a DPA. Reasons were categorized as confusion and misunderstanding regarding the legal system, mistrust, or social isolation. CONCLUSIONS: The high rate (79%) of DPA completion is probably related to individually counseling residents. However, competent residents who despite counseling do not choose to execute a DPA can have detailed advance directives ("living wills") prepared without appointing a decision-maker.     

Influence of dietary iron deficiency on acute metal intoxication

The frequent difficulties encountered in the diagnosis of pediatric sarcomas, caused by the lack of observable differentiation at the light microscopic level, has led to the routine use of immunohistochemistry in pediatric surgical pathology. To a large degree the advent of this staining technique has led to the correct assessment of many perplexing lesions that previously would have been given inconclusive diagnoses. However, with increased usage and testing, it has become apparent that there are few, if any, "magic bullets" in immunohistochemistry for pediatric pathologists. Thus, it behooves diagnosticians to be careful in the usage of this technique, to be aware of possible discrepancies in its results, and to remember the ancillary nature of its application. The following article will review selected markers commonly used in pediatric surgical pathology, from both previous reports and the author's perspective, and will briefly consider several new phenotypic markers which have potential utility with childhood sarcomas.