Cégep de Saint-Laurent

Abstract We describe the progress in the science and technology of stabilized a‐Se from its early use in xerography and xeroradiography to its present use in commercial modern flat panel X‐ray imagers and ultrasensitive video tubes which utilize impact ionization of drifting holes. Both electrons and holes can drift in stabilized a‐Se, which is a distinct advantage since X‐ray photogeneration of charge carriers occurs throughout the bulk of the photoconductive layer. An a‐Se photoconductor has to be operated at high fields to ensure that the photogeneration efficiency is sufficiently large to provide reasonable X‐ray sensitivity. However, at high fields, the dark current is unacceptably large in simple metal/a‐Se/metal devices, and special multilayer device structures need to be designed. The dark current decays with time and increases with the nominal applied field. The reduction of the dark current to a tolerable level was one of the key factors that lead to the commercialization of a‐Se X‐ray detectors. We discuss the origin of the dark current, and highlight some of the current challenges in the design of next generation detectors. We also discuss the origin of impact ionization in a‐Se, and its fruitful utilization in ultrasensitive imaging devices, including the Harpicon, which are likely to lead to new high detective quantum efficiency detectors.

Spodoptera frugiperda is a polyphagous lepidopteran pest that encounters a wide range of toxic plant metabolites in its diet. The ability of this insect to adapt to its chemical environment might be explained by the action of major detoxification enzymes such as cytochrome P450s (or CYP). Forty-two sequences coding for P450s were identified and most of the transcripts were found to be expressed in the midgut, Malpighian tubules and fat body of S. frugiperda larvae. Relatively few P450s were expressed in the established cell line Sf9. In order to gain information on how these genes respond to different chemical compounds, larvae and Sf9 cells were exposed to plant secondary metabolites (indole, indole-3-carbinol, quercetin, 2-tridecanone and xanthotoxin), insecticides (deltamethrin, fipronil, methoprene, methoxyfenozide) or model inducers (clofibrate and phenobarbital). Several genes were induced by plant chemicals such as P450s from the 6B, 321A and 9A subfamilies. Only a few genes responded to insecticides, belonging principally to the CYP9A family. There was little overlap between the response in vivo measured in the midgut and the response in vitro in Sf9 cells. In addition, regulatory elements were detected in the promoter region of these genes. In conclusion, several P450s were identified that could potentially be involved in the adaptation of S. frugiperda to its chemical environment.

Abstract Levels of PCB methyl sulfones (MeSO2-CBs) and DDE methyl sulfones (MeSO2-DDEs) have been determined in tissues from polar bear (Ursus martimus), beluga whale (Delphinapterus leucas), and false killer whale (Pseudorca crassidens) from the Canadian environment, and grey seal (Halichoerus grypus), otter (Lutra lutra), and wild mink (Mustela vison) from the Swedish environment. Up to 30 MeSO2-CB congeners and three MeSO2-DDE isomers were shown to be present in the analyzed tissues. The concentration of total MeSO2-CBs ranged from 0.1 to 21 μg/g extracted lipids. 3-MeSO2-2,5,2′,4′,5′-penta-CB is the dominating MeSO2-CB congener in all the analyzed samples, but the corresponding 4-MeSO2-CB also is present in high concentrations. A smaller number of MeSO2-CBs, always dominated by the meta-substituted MeSO2-CBs, were present in livers of grey seal, otter, and mink than in adipose tissue or muscle. In all studied mammals the concentrations of MeSO2-CBs were higher in liver than in blubber or muscle. Seven PCB congeners were identified as precursors of the PCB methyl sulfones: 2,4,2′,5′-tetra-CB (CB-49), 2,5,3′,4′-tetra-CB (CB-70), 2,4,5,2′,5′-penta-CB (CB-101), 2,3,4,5,2′,5′-penta-CB (CB-87), 2,3,6,2′,4′,5′-hexa-CB (CB-149), 2,3,4,2′,3′,6′-hexa-CB (CB-132), and 2,3,4,2′,5′-hexa-CB (CB-141). All species except beluga whale contained 3-MeSO2-4,4′-DDE, but at a much lower concentration in mink and otter than in the other mammals. Polar bear and grey seal liver also contained 2-MeSO2-4,4′-DDE. The concentrations of 2- and 3-MeSO2-DDE ranged from 0.01 to 1.3 μg/g extracted lipids. A hitherto unknown MeSO2-DDE isomer was determined in false killer whale blubber by GC-MS, along with 2- and 3-MeSO2-4,4′-DDE and several unknown MeSO2-penta-CBs and MeSO2-hexa-CBs. tris(4-chlorophenyl)methanol was identified in the aryl methyl sulfone fraction of polar bear liver and grey seal blubber samples.

Cannabinoids are analgesic in man, but their use is limited by their psychoactive properties. One way to avoid cannabinoid receptor subtype 1 (CB1R)-mediated central side-effects is to develop CB1R agonists with limited CNS penetration. Activation of peripheral CB1Rs has been proposed to be analgesic, but the relative contribution of peripheral CB1Rs to the analgesic effects of systemic cannabinoids remains unclear. Here we addressed this by exploring the analgesic properties and site of action of AZ11713908, a peripherally restricted CB1R agonist, in rodent pain models. Systemic administration of AZ11713908 produced robust efficacy in rat pain models, comparable to that produced by WIN 55, 212-2, a CNS-penetrant, mixed CB1R and CB2R agonist, but AZ11713908 generated fewer CNS side-effects than WIN 55, 212-in a rat Irwin test. Since AZ11713908 is also a CB2R inverse agonist in rat and a partial CB2R agonist in mouse, we tested the specificity of the effects in CB1R and CB2R knock-out (KO) mice. Analgesic effects produced by AZ11713908 in wild-type mice with Freund's complete adjuvant-induced inflammation of the tail were completely absent in CB1R KO mice, but fully preserved in CB2R KO mice. An in vivo electrophysiological assay showed that the major site of action of AZ11713908 was peripheral. Similarly, intraplantar AZ11713908 was also sufficient to induce robust analgesia. These results demonstrate that systemic administration of AZ11713908, produced robust analgesia in rodent pain models via peripheral CB1R. Peripherally restricted CB1R agonists provide an interesting novel approach to analgesic therapy for chronic pain.

Congo red (CR) has been shown to inhibit the accumulation in scrapie-infected cells of prion protein (PrP) in the abnormal protease-resistant form (PrP-res). However, it was not clear if this effect was due to a direct interaction of CR with either PrP-res or its protease-sensitive precursor (PrP-sen) or to a less direct effect on living cells. Here we show that CR inhibits PrP-res formation in a simple cell-free reaction composed predominantly of purified PrP-res and PrP-sen. Structurally modified CR analogues were also compared in both the cell-free conversion reaction and scrapie-infected neuroblastoma cells. Methylation of the central phenyl groups at the 2,2' positions diminished the inhibitory potency by > or = 10-fold. In contrast, there was little effect of 3,3' methylation of the phenyls, deletion of one phenyl, or addition of an amido group between the phenyls. The relative activities of these compounds were well correlated in both cellular and acellular systems. Molecular modeling indicated that CR and 3,3'-methyl-CR have little rotational restriction about the biphenyl bond and can readily adopt a planar conformation, as can phenyl-CR and amido-CR. In contrast, 2,2'-methyl-CR is restricted to a nonplanar conformation of the biphenyl group. Thus, planarity and/or torsional mobility of the central phenyl rings of CR and its analogues is probably important for inhibition of PrP-res formation. On the other hand, variations in the intersulfonate distance in these molecules had little effect on PrP-res inhibition. These results indicated a high degree of structural specificity in the inhibition of PrP-res formation by CR and related compounds.

Objective: Comparative study of CSF levels of tau and AD7C-neuronal thread protein (NTP) in patients with AD and control subjects. Background: AD is characterized by neurofibrillary tangles composed of the abnormally hyperphosphorylated microtubule-associated protein tau. AD7C-NTP is a proposed AD marker expressed at early stages of neurofibrillary degeneration. Methods: Enzyme-linked immunosorbent assays specific for tau and AD7C-NTP. CSF samples were obtained from 35 demented patients (25 with antemortem clinical diagnosis of probable AD, 5 with neuropathologic diagnosis of definite AD, 5 with Lewy body pathology), 29 nondemented patients with PD, and 16 elderly healthy control subjects. Receiver operating characteristics (ROC) and multivariate discriminant analysis for AD versus controls. Correlational analysis of CSF tau and AD7C-NTP and of each marker with Mini-Mental State Examination (MMSE) scores was performed. Results: Levels of both tau and AD7C-NTP were significantly elevated in the AD patients compared with control subjects. ROC analysis showed that CSF tau distinguished between patients with AD and nondemented control subjects with 63% sensitivity and 89% specificity, AD7C-NTP with 70% sensitivity and 87% specificity. Combined evaluation of both markers with discriminant analysis raised the specificity to 93% at a 63% sensitivity level. Both markers positively correlated with each other within the AD group, but not among control subjects. CSF levels of AD7C-NTP, but not of tau, showed a small but significant inverse correlation ( r = −0.43) with MMSE scores of AD patients. Conclusions: CSF levels of tau and AD7C-NTP may be useful biomarkers for AD.

Ecologically similar species may coexist when resource partitioning over time and space reduces interspecific competition. Understanding resource use within these species assemblages may help predict how species relative abundance might influence ecosystem functioning. In the Gulf of St. Lawrence, Canada, 4 species of rorqual whales (blue Balaenoptera musculus, fin B. physalus, minke B. acutorostrata and humpback Megaptera novaeangliae) coexist during the summer feeding period. They can be observed within hundreds of meters of one another, suggesting an overlap in ecological niches; yet fine-scale habitat use analyses suggest some resource partitioning.<br/>While major ecological changes have been observed in marine ecosystems, including the Gulf of St. Lawrence, we have little understanding of how the removal of predatory fish might<br/>cascade through ecosystems. Here, we take advantage of a 19 yr tissue collection subsequent to a fishery collapse (which occurred in 1992) to investigate trophic niche partitioning within a guild of<br/>rorqual whales following the loss of a key ecosystem component, groundfish. We analyzed stable isotope ratios for 626 rorqual individuals sampled between 1992 and 2010. Using Bayesian isotopic mixing models, we demonstrated that the 4 rorqual species segregated trophically by consuming different proportions of shared prey. An overall increase in δ15N values over the study period (post groundfish collapse), particularly for fin and humpback whales, suggested a progressive use of higher-trophic level prey, such as small pelagic fish, whereas the stability of blue whale diet over time confirmed their specialized feeding behaviour. This study provides the first longterm assessment of trophic ecology among rorqual populations on this Northwest Atlantic feeding ground, and evidence for differential resource use among large marine predators following ecosystem change.

Abstract Ataxia telangiectasia and Rad3-related (ATR) kinase protects genome integrity during DNA replication. RP-3500 is a novel, orally bioavailable clinical-stage ATR kinase inhibitor (NCT04497116). RP-3500 is highly potent with IC50 values of 1.0 and 0.33 nmol/L in biochemical and cell-based assays, respectively. RP-3500 is highly selective for ATR with 30-fold selectivity over mammalian target of rapamycin (mTOR) and more than 2,000-fold selectivity over ataxia telangiectasia mutated (ATM), DNA-dependent protein kinase (DNA-PK), and phosphatidylinositol 3-kinase alpha (PI3Kα) kinases. In vivo, RP-3500 treatment results in potent single-agent efficacy and/or tumor regression in multiple xenograft models at minimum effective doses (MED) of 5 to 7 mg/kg once daily. Pharmacodynamic assessments validate target engagement, with dose-proportional tumor inhibition of phosphorylated checkpoint kinase 1 (pCHK1) (IC80 = 18.6 nmol/L) and induction of phosphorylated H2A.X variant histone (γH2AX), phosphorylated DNA-PK catalytic subunit (pDNA-PKcs), and phosphorylated KRAB-associated protein 1 (pKAP1). RP-3500 exposure at MED indicates that circulating free plasma levels above the in vivo tumor IC80 for 10 to 12 hours are sufficient for efficacy on a continuous schedule. However, short-duration intermittent (weekly 3 days on/4 days off) dosing schedules as monotherapy or given concomitantly with reduced doses of olaparib or niraparib, maximize tumor growth inhibition while minimizing the impact on red blood cell depletion, emphasizing the reversible nature of erythroid toxicity with RP-3500 and demonstrating superior efficacy compared with sequential treatment. These results provide a strong preclinical rationale to support ongoing clinical investigation of the novel ATR inhibitor, RP-3500, on an intermittent schedule as a monotherapy and in combination with PARP inhibitors as a potential means of maximizing clinical benefit.

Abstract Purpose: PARP plays an important role in DNA repair. Veliparib, a PARP inhibitor, enhances the efficacy of platinum compounds and has been safely combined with carboplatin and paclitaxel. The primary endpoint of this phase II trial determined whether addition of veliparib to carboplatin and paclitaxel improved progression-free survival (PFS) in previously untreated patients with advanced/metastatic non–small cell lung cancer. Experimental Design: Patients were randomized 2:1 to carboplatin and paclitaxel with either veliparib or placebo. Veliparib (120 mg) or placebo was given on days 1 to 7 of each 3-week cycle, with carboplatin (AUC = 6 mg/mL/min) and paclitaxel (200 mg/m2) administered on day 3, for a maximum of 6 cycles. Results: Overall, 158 were included (median age, 63 years; male 68%, squamous histology 48%). Median PFS was 5.8 months in the veliparib group versus 4.2 months in the placebo group [HR, 0.72; 95% confidence interval (CI), 0.45–1.15; P = 0.17)]. Median overall survival (OS) was 11.7 and 9.1 months in the veliparib and placebo groups, respectively (HR, 0.80; 95% CI, 0.54–1.18; P = 0.27). In patients with squamous histology, median PFS (HR, 0.54; 95% CI, 0.26–1.12; P = 0.098) and OS (HR, 0.73; 95% CI, 0.43–1.24; P = 0.24) favored veliparib treatment. Objective response rate was similar between groups (veliparib: 32.4%; placebo: 32.1%), but duration of response favored veliparib treatment (HR, 0.47; 95% CI, 0.16–1.42; P = 0.18). Grade III/IV neutropenia, thrombocytopenia, and anemia were comparable between groups. Conclusions: Veliparib combination with carboplatin and paclitaxel was well-tolerated and demonstrated a favorable trend in PFS and OS versus chemotherapy alone. Patients with squamous histology had the best outcomes with veliparib combination. Clin Cancer Res; 23(8); 1937–44. ©2016 AACR.

Purpose The purpose of this article is to provide a more complete perspective regarding the “best practices” for performance appraisals of “distant” employees in global organizations. Design/methodology/approach A range of published works (1998‐2009) on multinational corporations and performance appraisals was reviewed. The literature was used to determine human resource challenges associated with globalization as well as the types of performance appraisals, common pitfalls and elements for improvement of appraisal systems. Concepts were then combined to determine the “best practices” for performance appraisal in a global setting. Finally, a small questionnaire consisting of six questions was constructed and sent to managers in two companies in the health care industry meeting the criteria of having “distant” employees. The questions were open‐ended in order to allow for a variety of responses enabling the researchers to view trends and make comparisons with the literature. Findings Adequate training must be provided to both the appraiser and the appraisee in order to avoid the many rating errors that are common in performance appraisal. Training should include cultural, legal and customer differences by country providing managers with the tools to improve on the process. Managers must also be given the opportunity to build the required relationship with these employees. Research limitations/implications A questionnaire was sent to several key managers in two complex pharmaceutical firms meeting the criteria with responses received. Further empirical research on the best practices of performance appraisal for distant employees in global organizations should be pursued. Practical implications This article provides a source of information on what practices are followed in order to support the performance appraisal of “distant” employees in different parts of the world. Originality/value There is limited literature dealing with “distant” employee performance appraisal in global organizations and this article attempts to fill this gap.

Myelofibrosis (MF) is a progressive chronic myeloproliferative neoplasm characterized by hyperactivation of JAK/STAT signaling and dysregulation of the transcription factor GATA1 in megakaryocytes (MKs). TGF-β plays a pivotal role in the pathobiology of MF by promoting BM fibrosis and collagen deposition and by enhancing the dormancy of normal hematopoietic stem cells (HSCs). In this study, we show that MF-MKs elaborated significantly greater levels of TGF-β1 than TGF-β2 and TGF-β3 to a varying degree, and we evaluated the ability of AVID200, a potent TGF-β1/TGF-β3 protein trap, to block the excessive TGF-β signaling. Treatment of human mesenchymal stromal cells with AVID200 significantly reduced their proliferation, decreased phosphorylation of SMAD2, and interfered with the ability of TGF-β1 to induce collagen expression. Moreover, treatment of MF mononuclear cells with AVID200 led to increased numbers of progenitor cells (PCs) with WT JAK2 rather than mutated JAK2V617F. This effect of AVID200 on MF PCs was attributed to its ability to block TGF-β1-induced p57Kip2 expression and SMAD2 activation, thereby allowing normal rather than MF PCs to preferentially proliferate and form hematopoietic colonies. To assess the in vivo effects of AVID200, Gata1lo mice, a murine model of MF, were treated with AVID200, resulting in the reduction in BM fibrosis and an increase in BM cellularity. AVID200 treatment also increased the frequency and numbers of murine progenitor cells as well as short-term and long-term HSCs. Collectively, these data provide the rationale for TGF-β1 blockade, with AVID200 as a therapeutic strategy for patients with MF.

Water quality degradation is a serious concern for the St. Lawrence River. While some environmental data are available for the St. Lawrence ecosystem, long‐term monitoring data are generally lacking. To infer past environmental changes, we undertook a paleolimnological assessment of diatom assemblages preserved in four 210 Pb‐ and 137 Cs‐dated sediment cores from two fluvial lakes in the river, and used diatom transfer functions to infer past shoreline habitat characteristics. At sites in Lake Saint‐François, a fluvial lake downstream from Cornwall, water quality decreased this century in response to human impacts (e.g. macrophyte density and nutrient levels increased). These trends were apparent from an increase in epiphytic diatom taxa, followed by an increase in eutrophic planktonic taxa. Water quality, however, appears to have improved somewhat in response to rehabilitation measures during the last two decades. From a sediment core near Montréal (Lake Saint‐Louis), we also noted a large proportion of eutrophic and epiphytic taxa, but less evidence was recorded of a recent improvement in water quality. The diatom‐based inference model for habitat characteristics appeared to reconstruct environmental conditions in the St. Lawrence River during the last century. The most notable shift has been an increase in diatom taxa commonly associated with macrophyte substrates. Trends in some of the planktonic diatoms were similar to those recorded in paleolimnological investigations from Lake Ontario, but cores from the river also may be reflecting local environments. This study shows that diatom‐based paleolimnological studies are possible in large river systems, if coring sites (e.g. fluvial lakes) are carefully selected.

The present study investigates the electrocoagulation-electroreduction (EC-ER) and ozonation process (ECRO process) for the treatment of grey wastewater (GWW) loaded with organic and inorganic matter, oil and greases (O&G), and total suspensions solids (TSS). Several factors, such as electrode materials, current density, electrolysis time, initial pH, wastewater conductivity, and ozone dosage were investigated. High treatment efficiency of GWW was recorded while applying the EC-ER technique followed by the ozonation process. The best performance for GWW treatment by the EC-ER process was obtained using aluminum and graphite electrodes operated at current density of 0.9 A/dm2, during 90 min of electrolysis time and at pH around 10 whereas the ozonation treatment of GWW was found to be more effective at pH 8 and at 9.2 g/h of ozone dosage. Under these optimal conditions, combining the electrochemical (EC-ER) and ozonation processes enhanced the removal of organic and inorganic contaminants from GWW. The ECRO process reduced total chemical oxygen demand (CODT) by 91.31±1.09%, total organic carbon (TOC) by 84.59±1.71%, soluble chemical oxygen demand (CODs) by 90.17±0.26%, and dissolved organic carbon (DOC) by 82.11±2.19%. Besides, the removal efficiency of biological organic demand (BOD), O&G, and total phosphorous (PT) reached 92.61±0.24%, 90.40±0.31%, and 86.66±0.00%, respectively.

The current Flight Management System (FMS), CMA-9000, from CMC Electronics - Esterline, only optimizes the vertical flight profile in terms of aircraft speeds. This article defines a methodology that optimizes the vertical flight profile in terms of speeds and altitudes, obtaining a trajectory that reduces the global flight cost.

In charmless $B\ensuremath{\rightarrow}PPP$ decays, where $P$ is a pseudoscalar meson, there are six possibilities for the symmetry of the final state. In this paper, for $P=\ensuremath{\pi},K$, we examine the properties of the fully-symmetric final state. We present expressions for all 32 $B\ensuremath{\rightarrow}PPP$ decay amplitudes as a function of both SU(3) reduced matrix elements and diagrams, demonstrating the equivalence of diagrams and SU(3). We also give 25 relations among the amplitudes in the SU(3) limit, as well as those that appear when the diagrams $E/A/PA$ are neglected. In the SU(3) limit, one has the equalities $\sqrt{2}\mathcal{A}({B}^{+}\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{)}_{\text{FS}}=\mathcal{A}({B}^{+}\ensuremath{\rightarrow}{K}^{+}{K}^{+}{K}^{\ensuremath{-}}{)}_{\text{FS}}$ and $\sqrt{2}\mathcal{A}({B}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{K}^{+}{K}^{\ensuremath{-}}{)}_{\text{FS}}=\mathcal{A}({B}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{)}_{\text{FS}}$, where FS denotes the fully-symmetric final state. These provide good tests of the standard model that can be carried out now by the LHCb Collaboration.

Abstract Herein we report the first enantioselective total synthesis of 3,5‐dimethylorsellinic acid‐derived meroterpenoids (−)‐berkeleyone A and its five congeners ((−)‐preaustinoids A, A1, B, B1, and B2) in 12–15 steps, starting from commercially available 2,4,6‐trihydroxybenzoic acid hydrate. Based upon the recognition of latent symmetry within D‐ring, our convergent synthesis features two critical reactions: 1) a symmetry‐breaking, diastereoselective dearomative alkylation to assemble the entire carbon core, and 2) a Sc(OTf) 3 ‐mediated sequential Krapcho dealkoxycarbonylation/carbonyl α‐ tert ‐alkylation to forge the intricate bicyclo[3.3.1]nonane framework. We also conducted our preliminary biomimetic investigations and uncovered a series of rearrangements (α‐ketol, α‐hydroxyl‐β‐diketone, etc.) responsible for the biomimetic diversification of (−)‐berkeleyone A into its five preaustinoid congeners.

Active pixel sensor (APS) circuits are an alternate to passive pixel sensor (PPS) circuits, which, while common in CMOS technology, have yet to be incorporated into commercial amorphous silicon (a-Si) large-area imagers. A proof-of-concept 64 × 64 APS array for low-exposure medical X-ray imaging is fabricated in a-Si technology and mated with an amorphous selenium photoconductor. Modulation transfer function (MTF) response and transient response for the APS imager indicate significant charge trapping at the top insulator/a-Se interface. MTF response indicates an effective fill factor of 94.5 % for a geometric fill factor of 57% at an electric field strength of 10 V/μm. Signal-to-noise ratio (SNR) performance from the prototype imager is comparable to a state-of-the-art commercially available a-Si PPS X-ray imager for X-ray exposures down to 1.5 μR using an RQA5 standard fluoroscopic characterization beam. Pixel design and fabrication process improvements are suggested to improve the SNR performance of the APS imager below 1.5 μR.

infection. VetParasitol 34: 159-163.7. Jeffrey M, O’Toole D, Smith T, Bridges AW: 1988, Immu-nocytochemistry of ovine sporozoan encephalitis and enceph-alomyelitis. J Comp Pathol 98:213-224.8. Jortner BS, Troutt HF, Collins T, Scarratt K: 1985, Lesions ofspinal cord parelaphostrongylosis in sheep. Sequential changesfollowing intramedullary larval migration, Vet Pathol 22:137-140.9. Leek RG, Fayer R: 1980, Amprolium for prophylaxis of ovine

PURPOSE: A numerical model and the experimental methods to study the x-ray exposure dependent change in the modulation transfer function (MTF) of amorphous selenium (a-Se) based active matrix flat panel imagers (AMFPIs) are described. The physical mechanisms responsible for the x-ray exposure dependent change in MTF are also investigated. METHODS: A numerical model for describing the x-ray exposure dependent MTF of a-Se based AMFPIs has been developed. The x-ray sensitivity and MTF of an a-Se AMFPI have been measured as a function of exposure. The instantaneous electric field and free and trapped carrier distributions in the photoconductor layer are obtained by numerically solving the Poisson's equation, continuity equations, and trapping rate equations using the backward Euler finite difference method. From the trapped carrier distributions, a method for calculating the MTF due to incomplete charge collection is proposed. RESULTS: The model developed in this work and the experimental data show a reasonably good agreement. The model is able to simultaneously predict the dependence of the sensitivity and MTF on accumulated exposure at different applied fields and bias polarities, with the same charge transport parameters that are typical of the particular a-Se photoconductive layer that is used in these AMFPIs. Under negative bias, the MTF actually improves with the accumulated x-ray exposure while the sensitivity decreases. The MTF enhancement with exposure decreases with increasing applied field. CONCLUSIONS: The most prevalent processes that control the MTF under negative bias are the recombination of drifting holes with previously trapped electrons (electrons remain in deep traps due to their long release times compared with the time scale of the experiments) and the deep trapping of drifting holes and electrons.

PURPOSE: To evaluate HsS (elastoviscous hylan surgical shield, 0.45%) as an alternative to repeated corneal irrigation with a balanced salt solution during cataract surgery. SETTING: York Finch General Hospital, Toronto, Ontario (Center A), and Centre Hospitalier de St. Laurent, St. Laurent, Quebec (Center B), Canada. METHODS: This dual-center, randomized, prospective clinical trial comprised 60 patients (40 at Center A; 20 at Center B) who had routine small incision cataract surgery (Center A, endolenticular phacoemulsification; Center B, Khoury manual phacofragmentation) with in-the-bag implantation of a posterior chamber intraocular lens. The corneal irrigating fluid was randomly assigned to be HsS or a balanced salt solution. The frequency of required applications, duration of efficacy of each application, and assessment of corneal moisture, clarity, transparency, and reflection in the HsS and balanced salt solution groups were recorded and compared. RESULTS: Mean frequency of applications was 13.9 per procedure in the balanced salt solution group and 1.3 per procedure in the HsS group (P = .0001). Mean duration of effectiveness per application was 23.4 minutes for HsS and 2.0 minutes for balanced salt solution (P = .0001). No significant differences in safety or effect on corneal health were observed between the two solutions. CONCLUSION: The HsS was significantly more effective than a balanced salt solution in maintaining corneal moisture, clarity, and transparency. The use of HsS may be a safer, more effective option in ophthalmic surgery because it minimizes the obstructed visualization of the surgical field caused by frequent corneal irrigation and loss of surgeon concentration.