Absolute electroluminescence and photoluminescence measurements were carried out on strain-balanced quantum well solar cells. Over a range of bias, a reduced radiative recombination in the wells was observed compared to a model assuming a constant quasi-Fermi level separation (QFLS) over the device thickness. This was interpreted as a QFLS suppression in the wells relative to the bulk of 18 and 5 meV, respectively, for the single and five well strain-balanced quantum well solar cells, consistent with previous results on strained single quantum well and double quantum well devices. The photoluminescence spectra at open-circuit voltage under illumination in the well agreed with the electroluminescence spectra in the light in contrast to some theoretical predictions. Generation of hot carriers in the wells could be the thermodynamically compensating phenomenon for the QFLS reduction.

Strain-balanced Quantum Well Solar Cells (SB- QWSCs) are radiatively dominated at concentrator current levels. Incorporating back surface mirrors on the back of the doped substrate leads to a reduction in this radiative recombination current while the non-radiative dark current at lower bias remains unchanged. This work extends a previous model of radiative dark currents to cells where the substrate is not a perfectly absorbing sink for emitted luminescence by including multiple passes of photons emitted by radiative recombination. The luminescence in such mirrored structures is reduced and the radiative dark current lower. The structure is suited to concentrator applications because it corresponds to the high efficiency limit where losses due to light re-emission are limited to the solid angle for absorption of solar radiation.

The incorporation of strain-balanced quantum wells into a GaAs solar cell extends the spectral response resulting in a photocurrent increase that can exceed the reduction in voltage performance, leading to higher overall efficiencies [1]. At concentrator current levels the main carrier loss mechanism is radiative recombination from the quantum wells. We have recently reported on evidence of hot carrier effects in the quantum well regions of GaAs based strain-balanced cells incorporating InGaAs quantum wells and GaAsP barriers [2]. This paper extends this work to a greater range of samples, and reports on a bias-dependent broadening in exciton luminescence observed in all samples at high biases. We present two possible interpretations of the data using different parts of the generalised Planck equation.

To the Editors: In 1986, the American Thoracic Society (ATS) first suggested a fixed ratio of forced expiratory volume in one second (FEV1) to forced vital capacity (FVC) <0.75 to define airflow obstruction 1. Subsequent ATS documents published in 1991 2 and 1995 3 generically defined airflow obstruction as a reduction of FEV1/FVC, without recommending any numerical cut-off point. By contrast, the European Respiratory Society (ERS) guidelines 4 suggested the diagnosis of airflow obstruction be based on a ratio of FEV1 to slow vital capacity (VC) <88 and <89% of predicted in males and females, respectively. These values were not arbitrarily chosen as they roughly correspond to the lower 95th percentiles of frequency distributions of a healthy population. More importantly, they are consistent with the well-known decrease of lung elastic recoil and, by inference, of forced expiratory flow with ageing. In 2001, the Global Initiative for …

Generalites 17S80 Spirometrie 17S81 Volumes pulmonaires 17S83 Capacite de diffusion du monoxyde de carbone 17S85 Les differents types d’anomalies respiratoires 17S86

Photon recycling in strain-balanced quantum well solar cells grown on distributed Bragg reflectors has been observed as a suppression of the dark current and a change in electroluminescence spectra. Comparing devices grown with and without distributed Bragg reflectors we have demonstrated up to a 33% reduction in the ideality n=1 reverse saturation current. Furthermore, to validate the observations we demonstrate how both the measured dark currents and electroluminescence spectra fit very well to a photon recycling model. Verifying our observations with the model then allows us to calculate optimized device designs.

Few studies have investigated the treatment and the outcomes of patients with catheter-related thrombosis (CRT).The RIETE registry (Registro Informatizado de Enfermedad TromboEmbólica [Computerized Registry of Patients with Venous Thromboembolism]) is a prospective international registry of consecutive patients with objectively confirmed venous thromboembolism (VTE). We analyzed the characteristics, treatment, and outcomes of patients with CRT.Of 558 patients with CRT, 45 (8%) presented with a pulmonary embolism (PE) concomitantly. More patients had central line-associated thrombosis compared with port systems, but catheter type did not influence the risk of presenting with a PE. Patients with only CRT were more often prescribed low-molecular-weight heparin for the duration of their anticoagulant treatment compared with patients presenting with concomitant PE. VTE recurrences and major bleeding events occurred frequently during treatment with anticoagulation (7 per 100 patient-years and 8.9 per 100 patient years, respectively). The rates of fatal PE recurrences (1.85 per 100 patient-years) and fatal bleeding (2.32 per 100 patient-years) were similar. Patients with an additional transient risk factor for VTE had the lowest risk for VTE recurrences (odds ratio [OR], 0.07; 90% confidence interval [CI], 0.01-0.45) compared with patients with CRT and no additional transient risk factors. PE at presentation increased the risk of recurrent thrombosis by 2.4 times. Renal insufficiency was also an independent predictor of recurrent thrombosis (OR, 3.93; 90% CI, 2.0-7.7). The odds of recurrent thrombosis was decreased by 77% in patients who received anticoagulation therapy for >90 days compared with patients with a shorter treatment (OR, 0.23; 90% CI, 0.1-0.56).Concomitant PE occurs less frequently in CRT than lower extremity deep venous thrombosis, but it is associated with a worse outcome. CRT occurs in high-risk patients, and duration of anticoagulation must be predicated on balancing these risks.

High-intensity focused ultrasound (HIFU) can achieve accurate and focused deep tissue ablation through an extracorporeal emission. Cardiac ablation using HIFU applied transthoracically must overcome potential interference from intervening thoracic structures. The aim of this study was to explore the efficacy and safety of septal ablation that was induced using transthoracic HIFU.Twenty-one canines were pretreated to improve acoustic transmission. Single ablations were induced by targeting transthoracic HIFU with acoustic power of 400 W for 3 sec at the middle and basal septum in eight canines. Extended ablations were performed to create larger lesions at the basal septum in eight more canines. The three-dimensional morphology of a basal septum lesion induced by a single ablation was analyzed. The temperature at the ablative targets was measured in the other five canines.The cardiomyocytes in the lesions underwent necrosis with a clear boundary. The three-dimensional morphology of the lesions appeared approximately as ellipsoids with a flatter endocardial side. The peak temperature at a power of 400 W for 3 sec was 93.27 ± 2.54°C, and it remained >50°C for nearly 10 sec. No procedure-related complications were observed.Ultrasound-guided transthoracic HIFU has the potential to safely create small dot or large mass lesions in the septum without a thoracotomy or a catheter.

SERIES “ATS/ERS TASK FORCE: STANDARDISATION OF LUNG FUNCTION TESTING” Edited by V. Brusasco, R. Crapo and G. Viegi Number 5 in this Series This section is written to provide guidance in interpreting pulmonary function tests (PFTs) to medical directors of hospital-based laboratories that perform PFTs, and physicians who are responsible for interpreting the results of PFTs most commonly ordered for clinical purposes. Specifically, this section addresses the interpretation of spirometry, bronchodilator response, carbon monoxide diffusing capacity ( D L,CO) and lung volumes. The sources of variation in lung function testing and technical aspects of spirometry, lung volume measurements and D L,CO measurement have been considered in other documents published in this series of Task Force reports 1–4 and in the American Thoracic Society (ATS) interpretative strategies document 5. An interpretation begins with a review and comment on test quality. Tests that are less than optimal may still contain useful information, but interpreters should identify the problems and the direction and magnitude of the potential errors. Omitting the quality review and relying only on numerical results for clinical decision making is a common mistake, which is more easily made by those who are dependent upon computer interpretations. Once quality has been assured, the next steps involve a series of comparisons 6 that include comparisons of test results with reference values based on healthy subjects 5, comparisons with known disease or abnormal physiological patterns ( i.e. obstruction and restriction), and comparisons with self, a rather formal term for evaluating change in an individual patient. A final step in the lung function report is to answer the clinical question that prompted the test. Poor choices made during these preparatory steps increase the risk of misclassification, i.e. a falsely negative or falsely positive interpretation for a lung function abnormality or a change …

Ground granulated blast furnace slag (GGBFS) and steelmaking slag have been used as a raw material for cement production or as an aggregate to make concrete, which contribute aluminum, calcium, iron, and silicon oxides. The suitability of the slag for a particular application depends on its reactivity, cost, availability, and its influence on the properties of the resulting concrete. For the interest of durability studying of concrete in the presence of slag, the accelerated carbonation products and leaching behavior of the slag and Portland cement (PC) were studied. The experimental results confirmed that the slag was more resistant to carbonation compared to PC. The carbonation degree of GGBFS reduced by 17.74%; and the carbonation degrees of steelmaking slags reduced by 9.51%-11.94%. Carbonation neutralized the alkaline nature of the hydrated pastes and gave rise to the redox potential of the leachate slightly (30-77 mV). The carbonation also increased the release of most of the elements presented, except for calcium, to the aqueous environment. It is concluded that blend cements (PC plus slag) have economical advantages and better durability compared to PC.

[⇓][1] SERIES “ATS/ERS TASK FORCE: STANDARDISATION OF LUNG FUNCTION TESTING” Edited by V. Brusasco, R. Crapo and G. Viegi Number 2 in this Series [1]: #F13

SERIES “ATS/ERS TASK FORCE: STANDARDISATION OF LUNG FUNCTION TESTING” Edited by V. Brusasco, R. Crapo and G. Viegi Number 1 in this Series ⇓In preparing the joint statements on lung function testing for the American Thoracic Society (ATS) and the European Respiratory Society (ERS), it was agreed by the working party that the format of the statements should be modified so that they were easier to use by both technical and clinical staff. This statement contains details about procedures that are common for many methods of lung function testing and, hence, are presented on their own. A list of abbreviations used in all the documents is also included as part of this statement. All terms and abbreviations used here are based on a report of the American College of Chest Physicians/ATS Joint Committee on Pulmonary Nomenclature 1. The metrology definitions agreed by the International Standards Organization (ISO) are recommended 2 and some important terms are defined as follows. Accuracy is the closeness of agreement between the result of a measurement and the conventional true value. Repeatability is the closeness of agreement between the results of successive measurements of the same item carried out, subject to all of the following conditions: same method, same observer, same instrument, same location, same condition of use, and repeated over a short space of time. In previous documents, the term reproducibility was used in this context, and this represents a change towards bringing this document in line with the ISO. Reproducibility is the closeness of agreement of the results of successive measurements of the same item where the individual measurements are carried out with changed conditions, such as: method of measurement, observer, instrument, location, conditions of use, and time. Thus, if a technician tests a subject several times, this is looking at the …

The strain balanced quantum well solar cell (SB-QWSC) provides a novel method of engineering the bandgap of a p-i-n junction to better match the terrestrial solar spectrum. The ability to accurately model the spectral response of a SB-QWSC is vital in optimising cell design. We present a study into two major components of such a model. Firstly, we provide an overview of the model for the confined energy levels within SB-QWSCs and outline the method used to determine a vital parameter for such calculations; the conduction band offset. Secondly, a critical evaluation of the hole in-plane effective masses (required to model the device absorption) is given. A multi-band k.p model is used to calculate the in-plane valence band dispersion and values for the effective masses are extracted from fits to the resulting E-k curves. The results of these investigations are then used to model the spectral response of a typical SB-QWSC. Good agreement is observed between absolute prediction and measured quantum efficiencies

A quantum well solar cell is a special multiple-band gap device with intermediate properties between heterojunction cells (sum of the currents generated in the different materials but voltage controlled by the lowest of the two band gaps) and tandem cells (sum of the voltages but current determined by the worst of the two sub-cells).Strain-balanced GaAsP/InGaAs multi-quantum wells move the absorption edge of GaAs solar cells closer to the optimum value for single junction cells with no need for any partially relaxed buffer layer to accommodate lattice mismatch between the absorbing layers and the substrate. Covering a large spectral range in a single-junction cell has the benefit that the cell remains close to optimal efficiency in the varying spectral conditions of a typical terrestrial concentrator. Though monolithic multi-junction cells have significantly higher efficiency, the series-current constraint means that some of this advantage is lost as the illuminating spectra and the cell temperature change from the values at which the tandem was optimised.The good material quality which can be achieved with these structures makes the cell dark current at the typical operating conditions expected under moderate sunlight concentration (similar to 200x), increasingly dominated by radiative processes the deeper the quantum wells.We will report on high concentration measurements of strain-balanced quantum well solar cells with and without Bragg-stack reflectors and discuss the "additivity" between the short-circuit current and the dark-current. We discuss a 50 shallow well cell with measured AM1.5d efficiency of (26 +/- 1)% at around 200 x concentration. This is approximately 2% higher than a comparable p-n cell with comparable material quality.The good material quality is also responsible for another effect previously observed in single quantum wells becoming measurable in structures with 5 and 10 wells, that is the suppression of carrier recombination in quantum wells with respect to expectations assuming that the quasi-Fermi level separation in the depletion region is equal to the cell output voltage throughout the active region. The latest results are presented together with possible explanations for this effect both in the dark and under illumination.Finally a brief discussion about the potential applications of quantum well solar cells completes the paper. (c) 2005 Elsevier B.V. All rights reserved.

Self-absorption or photon recycling (PR) has been observed experimentally as a reduction in the ideality n=1 reverse saturation current of SB-QWSCs. We believe this is the first example of PR effects on solar cell dark-currents. PR is observed at high bias when the primary recombination mechanism in SB-QWSCs is radiative recombination in the quantum wells corresponding to ideality n=1 dark-currents. Results are presented here on the effect of PR on the dark-current and electroluminescence (EL) spectrum; PR has resulted in DBR SB-QWSC dark-current and EL suppression of up to 35% both experimentally and theoretically. Comparison is made to control cells without a DBR. Modelling results will allow us to make predictions for expected efficiency enhancement in optimised SB-QWSC devices at high concentration levels. These results convincingly reveal how PR can increase the efficiency of SB-QWSCs.