DD Ratio Research Articles

Comparison of Cirrus spectral domain OCT with disc-macula distance to disc diameter ratio in diagnosing congenital optic nerve hypoplasia.

Diagnosis of congenital optic nerve hypoplasia (CONH) can be challenging in children or uncooperative individuals. Misdiagnosis can lead to inappropriate treatment; thus, it is important to identify an objective and reliable measurement. The purpose of this study was to evaluate whether Cirrus spectral domain optical coherence tomography (SD-OCT) is a valid test for diagnosing CONH by comparing it to the disc-macula distance to disc diameter (DM:DD) ratio. A total of 93 participants (64 controls and 29 CONH) underwent comprehensive eye examinations, fundus photography and Cirrus SD-OCT. Receiver operating characteristic (ROC) curves for the DM:DD ratio and OCT disc area were constructed for CONH and control eyes. Mean (±SD) OCT disc area was 1.46 (±0.42) mm2 and 1.89 (±0.38) mm2 for CONH and control eyes, respectively (p < 0.0001). The area under the curve for the DM:DD ratio was 0.97 (95% confidence interval: 0.91-0.99) and 0.79 for OCT disc area (95% confidence interval: 0.70-0.86), which were significantly different (p = 0.0005). The optimal cut-off value for OCT disc area was 1.66 mm2 (76% sensitivity, 70% specificity), while the optimal cut-off for DM:DD ratio was 3.10 (85% sensitivity and 95% specificity). The Cirrus SD-OCT showed a tendency to overestimate disc size, especially in cases with no light perception (NLP) or segmental CONH. Although the DM:DD ratio is superior to OCT in diagnosing CONH with a higher sensitivity and specificity, the ratio is subject to inter-examiner variability and can be challenging to obtain. We found the Cirrus SD-OCT to be a valid objective test for diagnosing CONH. Caution is advised when using SD-OCT in segmental CONH or in an eye with NLP. We suggest 1.66 mm2 as the optimal cut-off value for Cirrus SD-OCT disc area to differentiate a hypoplastic from a normal optic disc.

Vertical characterization of fine and coarse dust particles during an intense Saharan dust outbreak over the Iberian Peninsula in springtime 2021

Abstract. An intense and long-lasting Saharan dust outbreak crossed the Iberian Peninsula (IP) from the southwest (SW) to the northeast (NE) from 25 March until 7 April 2021. This work aims to assess the optical and mass contribution of both fine and coarse dust particles along their transport. Five Iberian lidar stations were monitoring the transport and evolution of the Saharan dust particles, i.e. El Arenosillo/Huelva, Granada, Torrejón/Madrid and Barcelona in Spain, and Évora in Portugal. The particular meteorological conditions determined the aerosol scenario along the overall dust event, differing in the first part of the event (25–31 March), in which the strongest dust incidence occurred on 29–31 March at the south and central stations and 1 April at Barcelona, from the second one (1–7 April). The use of the two-step POLIPHON algorithm showed the relevance of using polarized lidar measurements for separating the aerosol properties of dust fine and coarse particles as an added value. Both the fine dust (Df) and coarse dust (Dc) components of the total particle backscatter coefficient (total dust, DD = Dc + Df) were separately derived. The dust plume was well-mixed with height and no significant differences were found in the vertical structure of both the Dc and Df particle backscatter coefficients. From the beginning of the dust outbreak until 1 April, the vertical Df / DD mass ratio was nearly constant in time at each station and also in altitude with values of ∼ 10 %. Moreover, the mean dust optical depth at 532 nm was decreasing along that dust pathway, reporting values from SW to NE stations of 0.34 at El Arenosillo/Huelva, 0.28 at Granada, 0.20 at Évora, 0.28 at Torrejón/Madrid, and 0.14 at Barcelona, although its Df / DD ratio remained almost constant (28 %–30 %). A similar pattern was found for the total dust mass loading and its Df / DD ratio, i.e. mostly decreasing mean mass values were reported, being constant in its Df / DD ratio (∼ 10 %) along the SW–NE dust pathway. In addition, the episode-mean centre-of-mass height increased with latitude overall, showing a high variability, being greater than 0.5 km at the southern sites (El Arenosillo/Huelva, Granada, Évora) and ∼ 1.0 km at Torrejón/Madrid and Barcelona. However, despite the relatively high intensity of the dust intrusion, the expected ageing of the dust particles was hardly observed, by taking into account the minor changes found in the contribution and properties of the coarse and fine dust particles. This is on the basis that the IP is relatively close to the Saharan dust sources and then, under certain dust transport conditions, any potential ageing processes in the dust particles remained unappreciated. The following must be highlighted: the different relative contribution of the fine dust particles to the total dust found for their optical properties (∼ 30 %) associated with the radiative effect of dust, with respect to that for the mass features (∼ 10 %) linked to air quality issues, along the overall dust event by crossing the IP.

J-evaluation on tensile testing (JETT) based fracture toughness assessment of Aluminium (6063) alloy using circumferentially notched round bar specimens

The J-evaluation on tensile testing (JETT) using circumferential notch round bar specimens has been proposed for rapid determination of fracture toughness of structural materials exhibiting substantial ductile mode fracture. However, very little has been reported on the effect of notch parameters (notch diameter and notch angle) on the JETT fracture toughness values determined. In this study, Al 6063 alloy was used as test material, and the dependence of the fracture properties on notch parameters, investigated. The Al6063 alloy samples were machined having a constant gauge length (D) of 10 mm, notch diameters (d) of 6, 7, and 8 mm, and notch angles of 45, 60, and 75°, and subjected to tensile loading to fracture. The results obtained showed that the notch strength of the alloy increased with decrease in notch diameter and increased slightly with increasing notch angle. The percent elongation of the notch samples increased with increase in notch diameter and slightly with increase in notch angle. The JETT-fracture toughness values were observed to be more convergent with Dd ratio within the range 1.25–1.7 and the use of notch angles of 60 and 75° with an average value of 328.33 ± 23.73 kJ/m2 obtained. Notch angle of 45°, is not recommended for the JETT basis for evaluation of fracture toughness of Al 6063 alloy.

Integration of pain scores, morphine consumption and demand/delivery ratio to evaluate patient-controlled analgesia: the C-SIA score.

BackgroundPatient-controlled analgesia (PCA) is used to manage postoperative pain. Postoperatively, some patients need to be re-instructed on its correct use. This study explores the efficacy of re-instruction and illustrates a comprehensive version of the Silverman integrated approach (C-SIA), based on the integration of static and dynamic pain scores, morphine consumption, and the ratio between demanded and delivered PCA boluses (the DD ratio).MethodsIn total, 50 patients operated on for colorectal surgery were studied retrospectively. The change in DD ratio after re-instruction was analyzed as the primary endpoint. Re-instructed and not re-instructed subjects were compared according to DD ratio, pain scores, and morphine consumption. A secondary comparison was performed using the SIA and C-SIA scores, to illustrate the reliability of the latter tool. Agreement between C-SIA and SIA score was assessed using a Bland-Altman analysis.ResultsIn re-instructed patients, the DD ratio decreased after re-education (P = 0.011). Re-instructed patients had higher DD ratios (P = 0.018) and pain scores at rest (P = 0.024) and movement (P = 0.012) at 24 h after surgery than not re-instructed subjects. These differences disappeared at the 48 h visit. Both the SIA and C-SIA scores reflected these findings. C-SIA scores showed a higher coefficient of correlation with the DD ratio (r = 0.815; P < 0.001) than SIA scores (r = 0.663; P < 0.001). The C-SIA scores, in absolute values, being based on more variables, were, on average, 2.5 times the SIA score.ConclusionsRe-instruction is effective for optimizing PCA therapy. The C-SIA is an alternative to the SIA score that gives an overall measure of PCA therapy efficacy.

Thrombophilia in Pathological Pregnancies

Abstract Introduction. Many situations in pregnancy create a thrombophilia, which is believed to have a protective function, which is the result of the hormone influence, primarily by gestagenic hormones. This is a physiological condition and it helps in successful implantation of the embryo and prevention of bleeding. The presence of additional, hereditary or acquired cause of thrombophilia disrupts the natural balance and creates conditions for venous thromboembolism and consequences for pregnancy, such as miscarriage, intrauterine fetal death, delayed intrauterine growth, eclampsia and abruption of the placenta. Methods. The study was designed as a retrospective epidemiological cross-sectional study and was conducted at the Institute of Transfusion Medicine in Skopje in the period from June to October 2016. The study included patients with current pathological pregnancies. The following laboratory analyses were conducted in all patients: hemostasis, D-dimer, antithrombin III, protein C, protein S, antiphospholipid antibodies, lupus anticoagulant, MTHFR, factor V Leiden and prothrombin mutation. Results. The study included 41 patients, of whom 3 were excluded due to an insufficient medical history, 3 who were receiving corticosteroid therapy, 2 due to incomplete laboratory analyses and one patient with proven systemic lupus. Data analysis showed that family history of thrombophilia was present in 25%. The most common MTHFR mutation was recorded in 26 (82%) patients, followed by the factor V mutation present in 18 (55%) of the examined patients. AT III deficiency was detected in only one patient (2%). In 12 patients (35%) a disturbed ratio of DD vs. markedly shortened APTT or inappropriately low levels of DD was registered, which is an indirect indicatorof hypofibrinolysis. Conclusion. Pathologic pregnancy is a condition that is often associated with thrombophilia. Advanced age of a patient, family and personal history of thrombotic conditions indicate a high risk of complications in pregnancy. Due to the current increased frequency of high risk pregnancies associated with circulation problems with the placenta, there is a need for more frequent hemostatic examinations in pregnancy.

Achievement of Laser Fusion with High Energy Efficiency Using a Mixture of D and T Ions

A mixture of deuterium (D) and tritium (T) is the most likely fuel for laser-driven inertial confinement fusion (ICF) reactors and hence DD and DT are the fusion reactions that will fire these reactors in the future. Neutrons produced from the two reactions will escape from the burning plasma, in the reactor core, and they are the only products possible to be measured directly. DT/DD neutron ratio is crucial for evaluation of T/D fuel ratio, burn control, tritium cycle and alpha particle self-heating power. To measure this ratio experimentally, the neutron spectra of DD and DT reactions have to be measured separately and simultaneously under high neutron counting with sufficient statistics (typically within 10% error) in a very short time and these issues are mutually contradicted. That is why it is not plausible to measure this high priority ratio for reactor performance accurately. Precise calculations of the DT/DD neutron ratio are needed. Here, we introduce such calculations using a three dimensional (3-D) Monte Carlo code at energies up to 40 MeV (the predicted maximum ion acceleration energy with the available laser systems). In addition, the fusion power ratio of DD and DT reactions is calculated for the same energy range. The study indicates that for a mixture of 50% deuterium and 50% triton, with taking into account the reactions D(d,n)3He and T(d,n)4He, the optimum energy value for achieving the most efficient laser-driven ICF is 0.08 MeV.

Fuel ion ratio determination in NBI heated deuterium tritium fusion plasmas at JET using neutron emission spectrometry

The fuel ion ratio (nt/nd) is of central importance for the performance and control of a future burning fusion plasma, and reliable measurements of this quantity are essential for ITER. This paper demonstrates a method to derive the core fuel ion ratio by comparing the thermonuclear and beam-thermal neutron emission intensities, using a neutron spectrometer. The method is applied to NBI heated deuterium tritium (DT) plasmas at JET, using data from the magnetic proton recoil spectrometer. The trend in the results is consistent with Penning trap measurements of the fuel ion ratio at the edge of the plasma, but there is a discrepancy in the absolute values, possibly owing to the fact that the two measurements are weighted towards different parts of the plasma. It is suggested to further validate this method by comparing it to the traditionally proposed method to estimate nt/nd from the ratio of the thermal DD and DT neutron emission components. The spectrometer requirements for measuring nt/nd at ITER are also briefly discussed.

Do Islamic Banks Have Higher Credit Risk?

This research is undertaken to answer the question whether Islamic banks have higher or lower credit risk than that of their counterpart conventional banks. Since the onset of the financial crisis, researchers have debated over this issue and a growing literature has provided empirical evidence by comparing the stability or the credit risk of Islamic and conventional banks. One of the fundamental drawbacks of previous research that investigated the level of credit risk between these two banking systems is that methodologies used to calculate credit risk or stability of banks, are mostly based on accounting information only such as Z score, NPL ratio and loan loss reserve ratio. Deriving a conclusion whether Islamic banks have higher or lower credit risk based on solely accounting information could be misleading, since accounting based credit risk measurements have a number of limitations. This research contributes in this debate by using Merton’s distance to default model, a market based credit risk measurement technique, to measure the credit risk of 156 conventional and 37 Islamic banks from 13 economies between 2000 and 2012. For a comparative purpose, we also use both the Z score and the non-performing loan (NPL) ratio along with distance to default model to measure the credit risk across both banking systems. Our results show that, in general Islamic banks have significantly lower credit risk than conventional banks when credit risk is measured by DD and NPL ratio. In contrast, Islamic banks have higher credit risk when it is measured by Z score. Therefore, it is hard to draw a simple conclusion about whether Islamic banks have higher or lower credit risk than their counterparts’ conventional bank. This also implies that methodology used to measure credit risk plays an important role in deciding which banking system is safer.

Renin-angiotensin system gene polymorphisms among Saudi patients with coronary artery disease.

BackgroundThe polymorphisms in the components of the renin-angiotensin system (RAS) are important in the development and progression of coronary artery disease (CAD) in some individuals. Our objectives in the present investigation were to determine whether three RAS polymorphisms, angiotensin-converting enzyme insertion/deletion (ACE I/D), angiotensin receptor II (Ang II AT2 - C3123A) and angiotensinogen (AGT-M235T), are associated with CAD in the Saudi population. We recruited 225 subjects with angiographically confirmed CAD who had identical ethnic backgrounds and 110 control subjects. The polymerase chain reaction-restriction fragment length polymorphisms (RFLP) technique was used to detect polymorphisms in the RAS gene.ResultsWithin the CAD group, for the ACE I/D genotype, DD was found in 64.4%, 26.3% carried the ID genotype, and 9.3% carried the II genotype. Within the control group, the DD genotype was found in 56.4%, 23.6% carried the ID genotype, and 20% carried the II genotype. The odds ratio (OR) of the ACE DD vs II genotype with a 95% confidence interval (CI) was 2.45 (1.26-4.78), with p = 0.008. For the Ang II AT2 receptor C3123A genotype, within the CAD group, CC was found in 39.6%, 17.8% carried the CA genotype, and 42.6% carried the AA genotype. Within the control group, CC was found in 39.1%, 60.9% carried the CA genotype, and there was an absence of the AA genotype. The OR of the Ang II AT2 receptor C3123A CC vs AA genotypes (95% CI) was 0.01, with p = 0.0001. A significant association with CAD was shown. For the AGT-M235T genotype, within the CAD group, MM was found in 24.0%, 43.6% carried the MT genotype and 32.4% carried the TT genotype. Within the control group, MM was found in 26.4%, 45.5% carried the TT genotype and 28.2% carried the MT genotype. The OR of MM vs TT (95% CI) was 0.79 (0.43 to 1.46), which was insignificant.ConclusionsThere is an association between the ACE I/D and Ang II AT2 receptor C3123A polymorphisms and CAD, however, no association was detected between the AGT M235T polymorphism and CAD in the Saudi population.

Geochemical monitoring of volcanic lakes. A generalized box model for active crater lakes

In the past, variations in the chemical contents (SO42−, Cl−, cations) of crater lake water have not systematically demonstrated any relationships with eruptive activity. Intensive parameters (i.e., concentrations, temperature, pH, salinity) should be converted into extensive parameters (i.e., fluxes, changes with time of mass and solutes), taking into account all the internal and external chemical–physical factors that affect the crater lake system. This study presents a generalized box model approach that can be useful for geochemical monitoring of active crater lakes, as highly dynamic natural systems. The mass budget of a lake is based on observations of physical variations over a certain period of time: lake volume (level, surface area), lake water temperature, meteorological precipitation, air humidity, wind velocity, input of spring water, and overflow of the lake. This first approach leads to quantification of the input and output fluxes that contribute to the actual crater lake volume. Estimating the input flux of the volcanic fluid (Qf- kg/s) –– an unmeasurable subsurface parameter –– and tracing its variations with time is the major focus during crater lake monitoring. Through expanding the mass budget into an isotope and chemical budget of the lake, the box model helps to qualitatively characterize the fluids involved. The (calculated) Cl− content and dD ratio of the rising volcanic fluid defines its origin. With reference to continuous monitoring of crater lakes, the present study provides tips that allow better calculation of Qf in the future. At present, this study offers the most comprehensive and up-to-date literature review on active crater lakes.

Degradation mechanisms of current gain in NPN transistors

An investigation of ionization and displacement damage in silicon NPN bipolar junction transistors (BJTs) is presented. The transistors were irradiated separately with 90-keV electrons, 3-MeV protons and 40-MeV Br ions. Key parameters were measured in-situ and the change in current gain of the NPN BJTS was obtained at a fixed collector current (Ic = 1 mA). To characterise the radiation damage of NPN BJTs, the ionizing dose Di and displacement dose Dd as functions of chip depth in the NPN BJTs were calculated using the SRIM and Geant4 code for protons, electrons and Br ions, respectively. Based on the discussion of the radiation damage equation for current gain, it is clear that the current gain degradation of the NPN BJTs is sensitive to both ionization and displacement damage. The degradation mechanism of the current gain is related to the ratio of Dd/(Dd + Di) in the sensitive region given by charged particles. The irradiation particles leading to lower Dd/(Dd + Di) within the same chip depth at a given total dose would mainly produce ionization damage to the NPN BJTs. On the other hand, the charged particles causing larger Dd/(Dd + Di) at a given total dose would tend to generate displacement damage to the NPN BJTs. The Messenger–Spratt equation could be used to describe the experimental data for the latter case.

Differences in the satellite association pattern in the human population

The incidence and pattern of satellite association (sa) were studied in short-term lymphocyte cultures in a group of 5 mentally retarded patients and in 11 controls. In 4 of the 5 patients a second sample was studied after 8 months. All individuals in both groups had normal karyotype. It was demonstrated statistically that the incidence of sa showed no significant heterogeneity among the controls but a highly significant heterogeneity among the patients. No heterogenity was observed between the two samples of each patient. In a total number of 2,020 sa complexes analysed, the largest comprised 7 chromosomes and several included more than 3 D or 2 G chromosomes; thus homologous chromosomes necessarily took part in the same sa complex. Both in the patient and in the control group, certain individuals showed significant deviations from the expected 5: 8: 2 ratio of DD, DG and GG associations and from the 3: 2 ratio of participating D and G chromosomes. In addition of the total number of cells with sa, the numbers of association complexes per cell as well as the D: G ratio showed significant heterogeneity among the patients but no heterogeneity between the two samples from each patient or among the controls. These results indicate the existence in the human population of differences in the formation of satellite associations.

Photoacclimation in microphytobenthos and the role of xanthophyll pigments

Estuarine microphytobenthos are frequently exposed to excessively high irradiances. Photoinhibition in microalgae is prevented by various photophysiological responses. We describe here the role of the xanthophyll pigments in photoacclimation. The pigment composition of the microphytobenthos was studied in three European estuaries (Barrow, Ireland; Eden, UK; Tagus, Portugal). Using HPLC-analyses, microscale changes in biomass and pigment composition were monitored over short (hourly) and long (seasonal) time scales. In the Barrow estuary, the biomass of microphytobenthos (measured as chlorophyll a) increased significantly in the top 400–500 µm of the sediment surface within 1 h of emersion; simultaneously, the xanthophyll pool size (diadinoxanthin plus diatoxanthin, dd + dt) almost doubled. A more gradual conversion of dd into dt was observed, with the dt:dd ratio increasing from <0.1 at the start of emersion to >0.3 after 3 h emersion. Similar trends in the dt:dd ratio were observed in the surface sediments of the Eden and the Tagus estuaries. Higher ratios were recorded in the Tagus estuary, which may be explained by higher incident irradiance. In addition, seasonal studies carried out in the Eden and Tagus estuaries showed that the xanthophyll pool size increased by 10% in the summer months. The pool size was highest in the Tagus estuary. Concurrently, high values for the de-epoxidation state were recorded, with values for dt/(dt + dd) > 0.35 recorded in the summer. At the Eden, the ratio never exceeded 0.3. The de-epoxidation state was higher in winter than in summer, which was ascribed to the low winter temperatures. During a vertical migration study, a negative relationship between chlorophyll a and the de-epoxidation state was observed. It is suggested that this relationship originates from ‘micro-migration’ within the biofilm. Migration within the euphotic zone may provide an alternative means for cells to escape photodamage. In this paper, we propose that both xanthophyll cycling and ‘micro’-migration play an important role in photoacclimation and it appears that these processes operate in parallel to regulate the photosynthetic response.

Mechanistic studies of combustion-stimulated hydrogen generation from sodium borohydride

The mechanism of hydrogen evolution from sodium borohydride reaction with water is investigated for the case where the process is stimulated by metal (magnesium or aluminum) combustion in water, with H 2 yield ∼ 7 wt % . With this goal, process temperature, combustion velocity, reaction rates and product composition were studied experimentally using direct thermocouple measurements, video recording, TGA and XRD analysis. Both combustion temperature (950–1600 °C) and front velocity (0.05–0.4 cm/s) were found to increase with the amount of metal fuel in the mixture, correlating with the overall reaction heat effect. Kinetic parameters were estimated based on TGA measurements for temperatures 400–700 °C. Experiments demonstrate that mixtures of Mg / NaBH 4 / H 2 O exhibit higher conversion than Al / NaBH 4 / H 2 O . Using deuterated water and mass-spectral analysis of the HD to DD ratio in the evolved hydrogen, it was determined that combustion favors borohydride pyrolysis over hydrolysis.

An appraisal of the disc–macula distance to disc diameter ratio in the assessment of optic disc size

The disc–macula distance to disc diameter ratio (DM:DD ratio) has been advocated as a method of supporting the diagnosis of optic nerve hypoplasia. A DM:DD ratio of 3.00 has been claimed to be a satisfactory threshold value for this purpose. This study has critically evaluated the above claim and found a value of 3.00 to be too low. The threshold DM:DD ratio values for the diagnosis of unequivocal ONH for an adult population, 5 and 2 years of age were found to be respectively 4.20, 3.93 and 3.70, the values for the diagnosis of mild ONH being 3.68, 3.44 and 3.23. Lower computed values reduce the predictive power. The method of computation of the DM:DD ratio was modified to abolish potential error due to disc rotation and foveal displacement. In an adult population, there was no correlation between the DM:DD ratio and amblyopia or disc ovalness. There was a trend of increasing DM:DD ratio towards myopia and decreasing DM:DD ratio towards hypermetropia; the DM:DD ratio may therefore be falsely high in high myopia. DM:DD ratio values below threshold should therefore be interpreted with care until formal optic disc biometry can be performed.

An appraisal of the disc-macula distance to disc diameter ratio in the assessment of optic disc size.

The disc-macula distance to disc diameter ratio (DM:DD ratio) has been advocated as a method of supporting the diagnosis of optic nerve hypoplasia. A DM:DD ratio of 3.00 has been claimed to be a satisfactory threshold value for this purpose. This study has critically evaluated the above claim and found a value of 3.00 to be too low. The threshold DM:DD ratio values for the diagnosis of unequivocal ONH for an adult population, 5 and 2 years of age were found to be respectively 4.20, 3.93 and 3.70, the values for the diagnosis of mild ONH being 3.68, 3.44 and 3.23. Lower computed values reduce the predictive power. The method of computation of the DM:DD ratio was modified to abolish potential error due to disc rotation and foveal displacement. In an adult population, there was no correlation between the DM:DD ratio and amblyopia or disc ovalness. There was a trend of increasing DM:DD ratio towards myopia and decreasing DM:DD ratio towards hypermetropia; the DM:DD ratio may therefore be falsely high in high myopia. DM:DD ratio values below threshold should therefore be interpreted with care until formal optic disc biometry can be performed.

High fusion performance from deuterium-tritium plasmas in JET

High fusion power experiments using DT mixtures in ELM-free H mode and optimized shear regimes in JET are reported. A fusion power of 16.1 MW has been produced in an ELM-free H mode at 4.2 MA/3.6 T. The transient value of the fusion amplification factor was 0.95±0.17, consistent with the high value of nDT(0)τEdiaTi(0) = 8.7 × 1020±20% m-3 s keV,and was maintained for about half an energy confinement time until excessive edge pressure gradients resulted in discharge termination by MHD instabilities. The ratio of DD to DT fusion powers (from separate but otherwise similar discharges) showed the expected factor of 210, validating DD projections of DT performance for similar pressure profiles and good plasma mixture control, which was achieved by loading the vessel walls with the appropriate DT mix. Magnetic fluctuation spectra showed no evidence of Alfvénic instabilities driven by alpha particles, in agreement with theoretical model calculations. Alpha particle heating has been unambiguously observed, its effect being separated successfully from possible isotope effects on energy confinement by varying the tritium concentration in otherwise similar discharges. The scan showed that there was no, or at most a very weak, isotope effect on the energy confinement time. The highest electron temperature was clearly correlated with the maximum alpha particle heating power and the optimum DT mixture; the maximum increase was 1.3±0.23 keV with 1.3 MW of alpha particle heating power, consistent with classical expectations for alpha particle confinement and heating. In the optimized shear regime, clear internal transport barriers were established for the first time in DT, with a power similar to that required in DD. The ion thermal conductivity in the plasma core approached neoclassical levels. Real time power control maintained the plasma core close to limits set by pressure gradient driven MHD instabilities, allowing 8.2 MW of DT fusion power with nDT(0)τEdiaTi(0) ≈ 1021 m-3 s keV, even though full optimization was not possible within the imposed neutron budget. In addition, quasi-steady-state discharges with simultaneous internal and edge transport barriers have been produced with high confinement and a fusion power of up to 7 MW; these double barrier discharges show a great potential for steady state operation. © 1999, Euratom

Xanthophyll cycling in Phaeocystis antarctica:changes in cellular fluorescence

The xanthophyll cycle has been implicated as a possible photoprotective mechanism in higher plants and algae by dissipating excess excitation energy via non-photochemical q.uenching. To examine whether colonial Phaeocystis antarctica Karsten displays xanthophyll cycling, nutrient-replete cu l tu r~s were initially grown under limiting (40 pm01 quanta m 2 s ~ ' ) and saturating (280 pm01 quanta m-2 S' ) irradiances for photosynthesis and their responses to irradiance transitions were examined for 1 h under 4 treatments. The ~ I I v ~ v o chl-specific absorption coefficient [aml+,(h), m2 (mg chl a)-'] for the light-limiled cultures was initially lower than the light-saturated cultures while chlorophyll (chl) anormallzed fluorrscence yields were similar for both treatments. Increases in irradiance induced increases in the diatoxanthin to diadinoxanthin ratio (DT:DD, w:w) up to 9-fold whereas parallel decreases in Irradiance similarly decreased the DT:DD ratio. Light-induced Increases in DT concentration were reduced in cultures exposed to dithiothreltol (DTT), an inhibitor of DD to DT conversion. Short-term changes in DD and DT concentrations were attributed solely to xanthophyll cycling; no de novo synthesis of DD or DT was evident based on a constant sum of DD and DT in the 1 h expenmental perturbations. It was found that DD and DT de novo synthesis required long-term acclimation; the mass ratio at steady state of (DD+DT)/chl a was 0.1 and 0.4 for the low and high light treatments, respectively. Pooled results from treatment and control cultures showed a linear relationship between light-induced changes in DT/chl a concentration and F/chl a (fluorescence to chl a ratio) and the slopes depended on the initial photoacclimated state of the culture. Cellular fluorescence changes appeared to be physiologically based; aaph()L) did not change in response to abrupt irradiance changes. Xanthophyll cycling may enable P antarctica to tolerate both high light environments and sudden changes in irradidnce, which occur during austral spring due to shallow mixed layers and intermittent shading by ice or clouds.

The Disc-Macula Distance to Disc Diameter Ratio: A New Test for Confirming Optic Nerve Hypoplasia in Young Children

The disc-macula: disc diameter (DM:DD) ratio is the ratio of the horizontal distance between the center of the optic disc and the macula to the mean diameter of the optic disc, as evaluated from fundus photographs. The diagnosis of optic nerve hypoplasia may be difficult in cases in which the optic discs are slightly reduced in size, or when the double ring sign is absent and the condition is bilateral. The DM:DD ratio was calculated for six eyes of five children with ophthalmoscopically obvious optic nerve hypoplasia, 12 eyes of six children in whom the diagnosis of optic nerve hypoplasia was equivocal (but established by visual field examination and retinal red free photography), 13 eyes of eight children with optic atrophy, and 25 eyes of 17 children with normal optic discs. The DM:DD ratio was found to be significantly higher for both groups with optic nerve hypoplasia than for those with optic atrophy and the normal controls. For practical purposes, when the DM:DD ratio is greater than 3.0, the diagnosis of optic nerve hypoplasia should be seriously considered.

Luminescence tuning of 2,2'-bipyridine and 1,10-phenanthroline complexes of iridium(III) in fluid solution

Luminescence quantum yields, lifetimes, and spectra of a series of cis-dichlorobis(2,2'-bypyridine) and -(1,10-phenanthroline) complexes of Ir(III) in water, methanol, acetonitrile, and dimethlyformamide at 295/sup 0/K are reported. Two emission bands originating from states of dd* and d..pi..* or mixed d..pi..*-..pi pi..* parentage are observed when 2,2'-bipyridine, 1,10-phenanthroline, or 5,6-dimethyl-10-phenanthroline are the coordinated bidentate ligands. A single d..pi..* or mixed d..pi..*-..pi pi..* emission is observed when 4,7-diphenyl-1,10-phenanthroline or 4,4'-diphenyl-2,2'-bipyridine occupies coordination sites. In all cases, the emitting states are found to be in thermal equilibrium in the fluid solvents at 295/sup 0/K. The ratio of dd* to d..pi..* or mixed d..pi..*-..pi pi..* emission intensity is solvent dependent; the dd* emission is generally favored by water whereas the d..pi..* or mixed d..pi..*-..pi pi..* band is favored by the nonaqueous solvents. Lifetimes (tau) and overall quantum yields (Q) are strongly solvent dependent in all cases, displaying a range of values that differ by more than 2 orders of magnitude between water and acetonitrile in some instances. However, the tau/Q ratios are quite insensitive to solvent. The change of orbital parentage of the lowest excited state from dd* (IrCl/sub 2/(bpy)/sub 2//sup +/ or IrCl/sub 2/(phen)/sub 2//sup +/) to d..pi..* or mixed d..pi..*-..pi pi..* (IrCl/submore » 2/(4,4'-Phbpy)/sub 2//sup +/ indicate that these complexes would be useful to further studies of photochemical tuning.« less