8,149 research outputs found
Sensivity analysis and design calculations with biofiltration models
Biofiltration is a new technology for biological treatment of volatile organic compounds present in airstreams. It is a complex process and thus, engineering models which attempt to describe it are by necessity very involved and contain a large number of parameters.
In this study, two models describing biofiltration of airstreams carrying a single pollutant (VOC) were used in detailed parameter-sensitivity studies. One model concerned biofiltration under steady-state conditions, while the second described the transient behavior of the process. The intent of the sensitivity studies was to determine which model parameters need to be known with accuracy in order to allow for a good prediction of the size of a biofilter needed to achieve a Oven VOC-control objective. Studies with the steady-state biofiltration model have shown that accurate knowledge of the values of two kinetic parameters and the specific area of biofilm (and therefore the packing configuration) are essential. Studies with the transient model have revealed that in regards to transient behavior, the mass transfer coefficient is the most important design parameter.
Design calculations were also performed in this study for an integrated process involving soil venting and biofiltration for cleaning a contaminated aquifer. Preliminary results (based on a number of simplifying assumptions) have shown that the proposed concept is plausible in the sense that a reasonable biofilter size is adequate for remediating a site in a relatively short period of time. It was also found that a given mass of contaminant can be treated more efficiently (shorter time, smaller biofilter volume) under constant venting rate if the volume of the aquifer is smaller (i.e., when the residence time of air in the aquifer is larger). This finding could be taken advantage of through faster remediation of a spill (before it spreads), or if seasonal variations affect the size of the aquifer
Periodic Slab LAPW Computations for Ferroelectric BaTiO
Linearized augmented plane wave (LAPW) calculations are performed for
periodic (001) and (111) slabs of BaTiO to understand the effects of
surfaces on ferroelectric BaTiO. The (111) slab is found to be much less
stable than the (001) slab. The average surface energies are respectively 3700
erg/cm and 1600 erg/cm. The depolarization field is sufficiently large
in the ideal unrelaxated slab to completely inhibit the ferroelectric
instability. No mid-gap surface states are evident, but there are surface
states in the upper gap in the unrelaxed slab and at the top of the valence
band. The dangling surface Ti bonds self-heal making the Ti-O surface very
reactive and an excellent epitaxial substrate. The charge density on atoms only
one unit cell away from the surface are almost identical to the bulk.
Keywords: ferroelectric, surface, slab, electronic structure, depolarization,
BaTiO, thin filmComment: LaTeX (RevTex),10 pages, 3 PS figures ( fig. 1 and fig. 3 are color),
1 table, J. Phys. Chem. Solids, Proceedings of Third Williamsburg Workshop on
Fundamental Experiments in Ferroeletrics, T. Egami, edito
The Potential of Synergistic Static, Dynamic and Speculative Loop Nest Optimizations for Automatic Parallelization
Research in automatic parallelization of loop-centric programs started with
static analysis, then broadened its arsenal to include dynamic
inspection-execution and speculative execution, the best results involving
hybrid static-dynamic schemes. Beyond the detection of parallelism in a
sequential program, scalable parallelization on many-core processors involves
hard and interesting parallelism adaptation and mapping challenges. These
challenges include tailoring data locality to the memory hierarchy, structuring
independent tasks hierarchically to exploit multiple levels of parallelism,
tuning the synchronization grain, balancing the execution load, decoupling the
execution into thread-level pipelines, and leveraging heterogeneous hardware
with specialized accelerators. The polyhedral framework allows to model,
construct and apply very complex loop nest transformations addressing most of
the parallelism adaptation and mapping challenges. But apart from
hardware-specific, back-end oriented transformations (if-conversion, trace
scheduling, value prediction), loop nest optimization has essentially ignored
dynamic and speculative techniques. Research in polyhedral compilation recently
reached a significant milestone towards the support of dynamic, data-dependent
control flow. This opens a large avenue for blending dynamic analyses and
speculative techniques with advanced loop nest optimizations. Selecting
real-world examples from SPEC benchmarks and numerical kernels, we make a case
for the design of synergistic static, dynamic and speculative loop
transformation techniques. We also sketch the embedding of dynamic information,
including speculative assumptions, in the heart of affine transformation search
spaces
Genetic and Immune Predictors for Hypersensitivity Syndrome to Antiepileptic Drugs
Hypersensitivity syndrome reactions (HSR) to antiepileptic drugs (AED) are associated with severe clinical cutaneous adverse reactions (SCAR).Our aims are: to assess HSRs to AEDs using the in vitro lymphocyte toxicity assay (LTA) in patients who manifested HSRs clinically, to correlate LTA results with the clinical syndrome, to correlate LTA results with the human leukocyte antigen (HLA) allele B*1502 (HLA-B*1502) positivity in a Han Chinese-Canadian population, and to determine the cytokine network in this population. HSR patients developed fever and cutaneous eruptions in the presence or absence of organ involvement within 8 weeks of exposure to carbamazepine (CBZ), phenytoin (PHY) or lamotrigine (LTG). Control patients received AEDs without presenting HSR. We investigated 10 CBZ-HSR (4 presented with Stevens-Johnson syndrome (SJS)), 24 CBZ-controls, 10 PHY-HSR (4 presented with drug-induced liver injury (DILI)), 24 PHY-controls, 6 LTG-HSR (1 SJS and 1 DILI) and 24 LTG-controls. There were 30 Han Chinese individuals (14 HSR patients and 16 controls) in our cohort. LTA toxicity greater than 12.5%±2.5% was considered positive. Differences among groups were determined by analysis of variance. In addition, we measured cytokine secretion in the patient sera between 1 month and 3 years after the event. All Han Chinese individuals and 30% of Caucasians were genotyped for HLA-B*1502.A perfect correlation (r=0.92) was observed between positive LTA and clinical diagnosis of DILI and SJS/toxic epidermal necrolysis (TEN). HLA-B*1502 positivity in Han Chinese is a predictor of CBZ-HSR and PHY-HSR. HLA-B*1502-negative Han Chinese receiving only CBZ or a combination of CBZ-PHY tolerated the drug(s) clinically, presenting negative CBZ-LTA and PHY-LTA. However, 3 patients presenting negative CBZ-LTA and PHY-LTA, as well as negative HLA-B*1502, showed positive LTG-LTA (38%, 28% and 25%, respectively), implying that they should not be prescribed LTG. Three patients had LTA positive to both PHY and CBZ, and 3 others had LTA positive to both PHY and LTG. Clinically, all six patients presented HSR to both drugs that they tested positive to (cross-reactivity). Patients were grouped based on the clinical presentation of their symptoms as only rash and fever or a triad that characterizes "true" HSR (rash, fever and DILI or SJS/TEN). Levels of pro-inflammatory cytokines were significantly higher in patient sera compared to control sera. More specifically, the highest levels of tumor necrosis factor (TNF)-α was measured in patients presenting "true" HSR, as were the apoptotic markers Fas, caspase 8 activity and M30. We concluded that LTA is sensitive for DILI and SJS/TEN regardless of drug or ethnicity. HSR prediction will prevent AED-induced morbidity. In Han Chinese, HLA-B*1502 positivity is a predictor for CBZ-HSR and PHY-HSR. Its negativity does not predict a negative LTG-HSR. There is cross-reactivity between AEDs. Additionally, T-cell cytokines and chemokines control the pathogenesis of SJS/TEN and DILI, contributing to apoptotic processes in the liver and in the skin
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