Search

Gwyneth A van Rijn, 1 C Jasper F Wijnen, 1 Bart TH van Dooren, 2, 3 Yanny YY Cheng, 1 Jan-Willem M Beenakker, 1, 4 Gregorius PM Luyten 1 1Department of Ophthalmology, Leiden University Medical Center, Leiden, The Netherlands; 2Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands; 3Department of Ophthalmology, Amphia Medical Hospital, Breda, The Netherlands; 4C.J.Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, The NetherlandsCorrespondence: Gwyneth A van RijnDepartment of Ophthalmology, Leiden University Medical Center, Leiden, The NetherlandsEmail g.a.van_rijn@lumc.nlIntroduction: During our clinical practice and research, we encountered an interchangeability problem when using the SP-2000P and SP-3000P TopCon corneal specular microscopes (CSMs) (TopCon Medical Systems, Tokyo, Japan) regarding the endothelial cell count (ECC). We describe a method to improve interchangeability between these CSMs.Methods: Five consecutive good-quality endothelial cell photographs were obtained in 22 eyes of 11 subjects. An ECC comparison between the two CSMs was performed after (I) gauging and calibration by the manufacturer, (II) adjustment of the magnification, (III) correction after external horizontal and vertical calibration.Results: There was a statistically significant difference between the ECC of the SP-2000P and SP-3000P at the start. The SP-2000P counted an average of 500 cells/mm 2 more than the SP-3000P (p=0.00). After correction for magnification and determining a correction factor based on external calibration, the difference between the ECC of the SP-2000P and the SP-3000P was then found to be 0.4 cells/mm 2 and was not statistically significant (p=0.98).Discussion: We propose a method for improving interchangeability, which involves checking magnification settings, re-checking magnification calibration with external calibration devices, and then calculating correction factors. This method can be applied to various specular or confocal microscopes and their associated endothelial cell analysis software packages to be able to keep performing precise endothelial cell counts and to enable comparison of ECCs when a CSM needs to be replaced or when results from different microscopes need to be compared.Keywords: corneal endothelium, corneal endothelial cells, specular microscopy, endothelial cell count, endothelial cell density, corneal endothelial cell analysis

textabstractIntroduction: During our clinical practice and research, we encountered an interchangeability problem when using the SP-2000P and SP-3000P TopCon corneal specular microscopes (CSMs) (TopCon Medical Systems, Tokyo, Japan) regarding the endothelial cell count (ECC). We describe a method to improve interchangeability between these CSMs. Methods: Five consecutive good-quality endothelial cell photographs were obtained in 22 eyes of 11 subjects. An ECC comparison between the two CSMs was performed after (I) gauging and calibration by the manufacturer, (II) adjustment of the magnification, (III) correction after external horizontal and vertical calibration. Results: There was a statistically significant difference between the ECC of the SP-2000P and SP-3000P at the start. The SP-2000P counted an average of 500 cells/mm2 more than the SP-3000P (p=0.00). After correction for magnification and determining a correction factor based on external calibration, the difference between the ECC of the SP-2000P and the SP-3000P was then found to be 0.4 cells/mm2 and was not statistically significant (p=0.98). Discussion: We propose a method for improving interchangeability, which involves checking magnification settings, re-checking magnification calibration with external calibration devices, and then calculating correction factors. This method can be applied to various specular or confocal microscopes and their associated endothelial cell analysis software packages to be able to keep performing precise endothelial cell counts and to enable comparison of ECCs when a CSM needs to be replaced or when results from different microscopes need to be compared.

Nuclear science is a young science, less than a hundred years old, but the one that may in the end save the world from self-destruction; particularly if James Lovelock's Gaia Hypothesis is correct[1]. The current reliability, safety, life-capacity, and overall capability of nuclear power reactors signify that here hangs the key to a secure future for society including energy availability, predictable fuel costs, and a non-toxic environment.

For implantation of silicon dopant into gallium arsenide, sheet resistance and damage increase as the ion dose rate increases in the high-dose regime (>5.0 × 1013 cm−2). But, in the low-dose regime (

Control of threshold voltage during gallium arsenide (GaAs) Metal Semiconductor Field Effect Transistor (MESFET) processing is critical. Variation in the dose rate during ion implantation has previously been demonstrated to affect sheet resistance and peak damage fraction for doses of 5 × 1013 ions/cm2 and higher. In this high dose regime, sheet resistance and damage increase as the dose rate increases. This paper describes dose rate effects in the low dose regime, where traditional channel implants are done, i.e., for 29Si+ in the low 1012 ions/cm2 range. 29Si+ was implanted at 3 × 1012 ions/cm2 followed by a co-implant of 9Be+ at 1 × 1012 ions/cm2 into GaAs substrates. The silicon dose rate was varied from 3 nA/cm2 to 44 nA/cm2. The FET channel resistance varied by 4.0%, and was a direct function of the implanted beam current. Sheet resistance decreased as the beam current increased, which is in sharp contrast to results previously published for the high dose regime. Damage has been characterized and correlated to the electrical properties in the low dose regime. The results are compared to those for the high dose regime in order to more clearly define the differences associated with the inversion of the dose rate dependence between the low dose and high dose regimes.

The second harmonic generation (SHG) from alternate-layer Langmuir-Blodgett (LB) films of stilbazolium dyes and 4, 4'-dioctadecyl-3, 5, 3', 5'-tetramethyldipyrryl-methene hydrobromide increases as I 2ω(N) = l 2ω(1) N 2 for N ≥ 2 bilayers, but the equivalent monolayer signal ( I 2ω(1) ) is significantly less than the intensity from LB monolayers of the corresponding dye on glass. This is attributed, in part, to the different molecular tilts and, in part, to the position of the anion which influences the charge distribution within the chromophore. For alternate-layer films of E-N-octadecyl-4-[2-(4-dimethylaminophenyl)ethenyl]pyridinium octadecylsulphate (dye I) the second-order susceptibility and chromophore tilt angle are χ (2) zzz = 45 pm V -1 and ϕ = 30° respectively, whereas the methoxy congener, E-N-octadecyl-4-[2-(4-methoxyphenyl)ethenyl]pyridinium octadecylsulphate (dye II), has χ (2) zzz = 11 Pm V -1 and ϕ = 35°. The nonlinear optical properties of such films are dependent upon the compatibility of the dye and spacer.

This study explored whether reactions to the Cancer Genetics Network (CGN) or CGN enrollment differed by receipt of a standard informational brochure versus a targeted version addressing factors previously associated with African Americans’ health behavior decisions and research participation. The 262 participants, identified through tumor registries or clinic contacts, were mailed brochures and completed phone interviews. When asked whether – based on the brochure – they were or were not ‘leaning toward’ CGN enrollment, about 75% of both standard and targeted groups reported leaning toward. When given the opportunity at the end of the interview, 68% enrolled in the CGN. Trust was strongly related to enrollment. Less education, less satisfaction with cancer care, and individualistic rather than collective orientation were associated with lower trust. Education was also bivariately associated with enrollment, but mediation analysis indicated that the operational mechanism of education’s influence on enrollment was through trust.

Shallow trench isolation (STI) is being scaled down in both width and depth to increase device packing densities. Critical to the success of interwell isolation is the accurate placement of the n-well/p-well junction in the center of the region below the STI oxide. Zero degree implants avoid shadowing effects from resist features but can reduce process robustness due to channeling-induced profile variations. The shape of dopant profiles near 0d tilt vary significantly with tilt angle changes too small to control on even advanced ion implanters. We modeled 150nm devices with a 380nm n+/p+ spacing and show that these profile variations lead to significant shifts in transistor threshold voltage and n-well to n+ leakage. We calibrated our simulator with SIMS data to accurately model transistor and interwell breakdown performance for 0d well implants for the first time. We also modeled the same structures made with implants at 3d tilt using quad repositioning. Low angle quad implants for retrograde wells eliminate shadowing effects while delivering superior process robustness as compared to 0d well implants.

Known amounts of carbon were implanted into a set of Si1−xGex alloy films (0

In eight isolated dog lobes, we examined the change in extra-alveolar perimicrovascular hydrostatic pressure (Pis) due to lung inflation. The vasculature was filled with autologous plasma. Pulmonary arterial and venous lines were connected to a common plasma reservoir. Perimicrovascular volume change (delta Vis), compliance (Cis), and the microvascular filtration coefficient (Kf) were derived from the change in lobe mass over time following a step increase in vascular pressure (Piv). Initially, transpulmonary pressure (PL) was 5 cmH2O and Piv = 0 cmH2O. At constant Piv, two sequential 5-cmH2O increases in PL increased Vis; division of delta Vis by Cis yielded the change in Pis attributable to lung inflation. Cis was 0.035 +/- 0.018 g X cmH2O–1 X g dry mass-1 (mean +/- SD) at PL = 15 cmH2O. Kf was 0.019 +/- 0.023 g X min-1 X cmH2O–1 X g dry mass-1. With inflation from PL = 5 to PL = 10 cmH2O, Pis = -2.15 +/- 1.76 cmH2O; from PL = 10 to PL = 15 cmH2O, Pis = -2.25 +/- 1.50 cmH2O. This perimicrovascular pressure change is very close to the perihilar interstitial pressure change reported by others. Such near equality suggests that the stress of lung inflation is very uniformly applied to the interstitial continuum.

Dependency of oxygen consumption (VO2) on oxygen delivery (DO2) in patients with adult respiratory distress syndrome and with congestive heart failure has been reported previously. We evaluated this relationship in 11 patients with pulmonary hypertension, 8 with primary pulmonary hypertension (PPH), and 3 with pulmonary hypertension secondary to chronic obstructive lung disease (SPH) at baseline and during treatment with vasodilating calcium channel antagonists. The mean baseline DO2 and VO2 were 11.0 +/- 4.2 and 3.9 +/- 1.1 ml/min/kg, respectively. After increasing cardiac output via vasodilators, we obtained an average of 3 additional data points per patient. We found a significant relationship between changes in VO2 and changes in DO2 (delta VO2 = -0.19 +/- 0.27 x delta DO2; r = 0.88, n = 37). In 4 patients, VO2 was determined both by respired gas analysis and by calculation from thermodilution cardiac output and measured arteriovenous oxygen gradient; results by the 2 methods were virtually identical. There was no significant relationship between cardiac output and mixed venous oxygen content or mixed venous oxygen tension (r = 0.20 and 0.47, respectively). Mean baseline oxygen extraction ratio was 36.7 +/- 6.4% and did not increase significantly after vasodilator therapy. We conclude that in patients with pulmonary hypertension, changes in oxygen consumption appear to be dependent on changes in oxygen delivery. This may represent evidence of tissue hypoxemia, which is otherwise not apparent. This dependency may support the use of vasodilators in these patients.

In the West model of zonal distribution of pulmonary blood flow, increases in flow down zone 2 are attributed to an increase in driving pressure and a decrease in resistance resulting from recruitment and distension. The increase in flow down zone 3 is attributed to a decrease in resistance only. Recent studies indicate that, besides the pressure required to maintain flow through a vessel, there is an added pressure cost that must be overcome in order to initiate flow. These additional pressure costs are designated critical pressures (Pcrit). Because Pcrit exceed alveolar pressure, the distinction between zones in the West model becomes less secure, and the explanation for the increase in flow even in West zone 3 requires reexamination. We used two methods to test the hypothesis that the Pcrit is the pertinent backpressure to flow even in zone 3, when the pulmonary venous pressure (Ppv) exceeds alveolar pressure (PA) but is less than Pcrit in the isolated canine left caudal lobe. First, PA was maintained at 5 cmH2O, and pressure flow (P-Q) characteristics were obtained in zone 2 and zone 3. Next, with PA still at 5 cmH2O, we maintained a constant flow and measured the change in pulmonary arterial pressure as Ppv was varied. Both techniques indicated that the pertinent backpressure to flow was the greater of either Pcrit or Ppv and that PA was never the pertinent backpressure to flow. Also, our results indicate no significant change in the geometry of the flow channels between zone 2 and zone 3. These findings refine the zonal model of the pulmonary circulation.

We studied the relationship between the pulmonary artery wedge pressure (Pw) and pulmonary venous pressure (Ppv) at 2 alveolar pressures (PA) in 7 isolated perfused dog lobes. If PA were the critical pressure in the pulmonary circulation, one would expect Pw to equal Ppv for all Ppv greater than PA. Relative to the hilum, the average critical pressure in these lobes was 15.07 +/- 0.40 cmH2O at PA = 5 cmH2O and increased significantly to 17.23 +/- 0.82 cmH2O at PA = 7 cmH2O. Because the critical pressure in fact exceeded PA, Pw was found to be relatively constant and independent of Ppv even when Ppv exceeded PA by 5 cmH2O or more. For example, at PA = 5.13 +/- 0.04 cmH2O and Ppv = 9.64 +/- 0.28, the mean value for Pw was 13.30 +/- 0.59 cmH2O. Pw is equal neither to the average critical pressure nor to PA, but instead lies between these two values. It is determined by the spectrum of closing pressures in the pulmonary circulation, and the time-constants for drainage of beds downstream from the occluded pulmonary arterial branch.

We performed YAG laser photoresection in 11 patients with tracheal or mainstem bronchial obstruction due to malignant or benign disorders. We used maximal inspiratory-expiratory flow-volume loops and expiratory volume-time plots to assess air flow limitation. Forced vital capacity (FVC), forced expiratory volume in one second (FEV1), peak expiratory flow (PEF) and iso-volume maximal flows at 50 percent of forced inspiratory and expiratory volume were calculated. Spirograms and flow-volume loops were repeated within 12 to 72 hours of laser resection. All patients had flattened expiratory limbs on their flow-volume loops. All spirometric parameters increased significantly following laser photoresection. In particular, peak flow improved in all patients, and FEV1 improved in nine of 11 patients, even though four patients had moderate to severe obstructive ventilatory defects which persisted after resection and were probably due to longstanding chronic obstructive pulmonary disease. We conclude that flow-volume loops and spirometry are helpful in assessing the site and nature of malignant large airway obstructive processes and, moreover, provide reliable information for evaluating the efficacy of laser photoresection. Serial physiologic studies indicate changes in the caliber of the upper airways and can be used as a simple means of following these patients.

We compared two modes of aerosol bronchodilator delivery in 34 patients hospitalized with obstructive airways diseases. The standard mode, therapist-administered up-draft nebulization (UDN), is labor-intensive and therefore relatively costly. The alternative mode, self-administration by a metered dose inhaler (MDI), is less costly, but its efficacy over an entire hospitalization has heretofore not been established. Patients were enrolled after transfer to the pulmonary ward from the emergency room or intensive care units (ICU). We then randomized them to receive metaproterenol q4h either via MDI or UDN. Daily spirometry revealed that MDI and UDN were associated with equivalent bronchodilation initially and equivalent improvement at discharge. The duration of hospitalization for the two groups was also the same. Thus, the two delivery methods were equally effective. We could not attribute this equivalence to pretreatment intergroup differences or to differences in concomitant therapy with steroids, theophylline, other bronchodilators, or antibiotics. Routine use of MDI rather than UDN in all non-ICU adult patients would save $253,487 per year at our institution alone.

We previously have shown that in patients with adult respiratory distress syndrome (ARDS) oxygen consumption (VO2) is linearly related to oxygen delivery (DO2) below a threshold DO2 of 21 ml/min/kg. To evaluate this relationship in chronic congestive heart failure (CHF), we studied eight patients with chronic CHF at baseline and during treatment with nitroglycerin. The resting DO2 and VO2 were 10.7 +/- 2.3 ml/min/kg and 3.8 +/- 0.87 ml/min/kg, respectively. In our eight patients, we found a significant relationship between changes in VO2 and in DO2 (delta VO2 = 0.16 + 0.34 X delta DO2, r = 0.84, n = 29). There was no significant relationship between DO2 and mixed venous oxygen tension (PvO2, r = 0.16), nor was there a significant relationship between cardiac output (Qt) and PvO2 (r = 0.21). We conclude that in patients with chronic CHF, changes in VO2 appear to be dependent on changes in DO2. This may represent an adaptive tissue response to chronically reduced systemic oxygen transport.

Pulmonary vasodilators are variably efficacious in primary pulmonary hypertension (PPH). None has consistently improved hemodynamics enough to obviate the need for complex and potentially hazardous testing of several vasodilators. Prostaglandin E1 (PGE1), a potent, short-acting pulmonary vasodilator, was administered to seven patients with PPH in order to determine whether PGE1 could accurately predict the hemodynamic and gas exchange effects of other commonly used vasodilators. Prostaglandin E1, nifedipine and hydralazine were administered to the patients while measuring pulmonary and systemic hemodynamics and arterial blood gases. Prostaglandin E1 was easily titrated but was inconsistent as a predictor of the effects of the other vasodilators with respect to pulmonary artery pressure, cardiac output and adverse effects on arterial oxygenation. This study suggests that patients with PPH must still receive carefully monitored trials of several vasodilators to determine whether there is a beneficial response and to select the appropriate treatment.

We studied the relationship between the pulmonary artery wedge pressure (Pw) and pulmonary venous pressure (Ppv) at 2 alveolar pressures (PA) in 7 isolated perfused dog lobes. If PA were the critical pressure in the pulmonary circulation, one would expect Pw to equal Ppv for all Ppv greater than PA. Relative to the hilum, the average critical pressure in these lobes was 15.07 +/- 0.40 cmH2O at PA = 5 cmH2O and increased significantly to 17.23 +/- 0.82 cmH2O at PA = 7 cmH2O. Because the critical pressure in fact exceeded PA, Pw was found to be relatively constant and independent of Ppv even when Ppv exceeded PA by 5 cmH2O or more. For example, at PA = 5.13 +/- 0.04 cmH2O and Ppv = 9.64 +/- 0.28, the mean value for Pw was 13.30 +/- 0.59 cmH2O. Pw is equal neither to the average critical pressure nor to PA, but instead lies between these two values. It is determined by the spectrum of closing pressures in the pulmonary circulation, and the time-constants for drainage of beds downstream from the occluded pulmonary arterial branch.

In 8 anesthetized dogs, during isocapnic hyperoxia we studied the effect of assisted ventilation (AV) on ventilatory drive, inspiratory off-switch volume (Voff) and duration of inspiratory diaphragmatic activity (Tdi). Tidal volumes (Vt) during AV were double spontaneous Vt. Two electrodes were inserted in the diaphragm to obtain the electromyogram (EMG). The index of ventilatory drive was the EMG 0.3--i.e., the amplitude of the moving average EMG 300 ms after the onset of inspiratory activity. AV decreased EMG 0.3 but had no effect on Voff and Tdi. Vagotomy not only abolished the reduction in drive, but may have increased drive during AV.