Retinoblastoma caused by an RB1 variant with unusually low penetrance in a Danish family.

Retinoblastoma is the most common eye cancer in children. It is caused by pathogenic alterations of both alleles of the tumor suppressor gene RB1. In heritable retinoblastoma, a constitutional RB1 variant predisposes the cells to tumor formation, and loss of the other allele is a prerequisite for the development of retinoblastoma. Heritable retinoblastoma is inherited in an autosomal dominant manner; however, the majority of cases are the result of a de novo pathogenic RB1 variant. Penetrance is usually high (>90%), but with marked inter-familial variability. In some families, penetrance is incomplete and family members who develop tumors tend to remain unilaterally affected. Moreover, some families with low penetrance also show a parent-of-origin effect. We describe a patient with unilateral retinoblastoma caused by a previously unreported likely pathogenic RB1 variant (c.1199T>C) that disrupts a highly conserved amino acid residue within the A-box functional domain. Segregation analysis showed that the variant had unusually low penetrance as nine non-affected family members carried the same variant. We emphasize the use of genetic analysis on tumor DNA for classifying the RB1 variant, and underline the challenges in clinical management and counseling of families carrying the specific RB1 variant.

Adding value to beef portion steaks through measuring individual marbling.

The current Meat Standards Australia (MSA) and AUS-MEAT grading system assumes that marbling through the M. longissmus thoracis et lumborum (loin) is represented by the score of the grading site. However, studies have indicated marbling varies within the beef loin, but commercially individual portion steaks are not graded for marbling. Cube rolls from a wide phenotypic marbling range (n = 102) were collected and sliced into 15 mm portion steaks, which were imaged with a Marel vision scanner to obtain objective marbling scores. Additionally, three locations (grading site, middle, cranial) across each cube roll were tested for intramuscular fat percentage (IMF%). The effect of steak location demonstrated marked variation across the length of the cube roll for both vision scanner marbling scores and IMF%. This variation in vision scanner marbling scores, expressed in units of MSA marbling score, equated to 316 MSA units. This work suggests an opportunity for individual portion marbling measurements and segregation of individual portion cut steaks based upon their marbling levels.

Prediction of chemical intramuscular fat and visual marbling scores with a conveyor vision scanner system on beef portion steaks.

This study describes the performance of a Marel conveyer vision scanner, across beef carcases (n = 102) from a wide visual marbling score range, in its ability to predict chemical intramuscular fat (IMF%), Meat Standards Australia (MSA) and AUS-MEAT marbling scores of portion steaks. Vision scanner marbling scores were acquired on fresh-cut steaks, with its predictions tested using a leave-one-out cross validation method, which demonstrated precise and accurate predictions of IMF% (R2 = 0.87; RMSEP = 1.16; slope = 0.09; bias = 0.22), MSA (R2 = 0.82; RMSEP = 70.11; slope = 0.09; bias = 17.08) and AUS-MEAT marbling (R2 = 0.79; RMSEP = 0.75; slope = 0.16; bias = 0.08). Care must be taken when calibrating devices on non-fresh-cut steak, as fresh-cut steaks produced different vision scanner marbling values suggesting different prediction equations are warranted. The Marel vision scanner prediction of visual grader scores was relatively less precise and accurate than its prediction of IMF%, however in this case it may have been due to error in the grader scores.

Danish heritable retinoblastoma survivors' perspectives on reproductive choices: "It's important for me, not to pass on this condition".

Despite reporting an overall normal life, survivors of heritable retinoblastoma face numerous physical and psychosocial issues. In particular, reproductive decision-making is often complex and difficult. This study aims to examine survivors' reflections on passing on heritable retinoblastoma to their children, how survivors approach their reproductive choices, and how the healthcare system can optimize counseling and support. Semi-structured interviews with Danish adult survivors of heritable retinoblastoma were qualitatively analyzed to explore their experiences. Participants were recruited from the Retinoblastoma Survivorship Clinic, Aarhus University Hospital, Denmark. Thematic data analysis was conducted followed by a condensing process specifically for the subthemes relating to reproductive choices. A common subtheme for all participants was a strong wish to avoid passing on retinoblastoma to their children. The participants emphasized the various medical, practical, emotional, and moral issues impacting their final reproductive choice in the process of family planning to conceive a child unaffected by retinoblastoma. Some had no option other than to conceive naturally and hope for an unaffected baby; while others weighed the pros and cons of choosing natural conception with prenatal testing and then considering termination of pregnancy (in case of an affected fetus) versus choosing fertility treatment with preimplantation genetic testing to achieve an unaffected pregnancy. Several participants underlined the complexity of their decisions, and also expressed feelings of guilt, both toward their affected child, and guilt for putting their partner through many difficult decisions and obstacles due to their genetic condition. Our findings demonstrate how one family-planning decision is not unequivocally "better" or easier than another. Healthcare professionals must provide the necessary information and tools to support the individual's unique decision-making process. Survivors' autonomy and individual needs, as well as the numerous and diverse aspects of heritable retinoblastoma, should be carefully considered.

Evaluation of competency-driven training for facilitators delivering a psychological intervention for children in Lebanon: a proof-of-concept study.

AIMS: The mounting evidence for effective delivery of psychological interventions by non-specialists in low- and middle-income settings has led to a rapid expansion of mental health and psychosocial support trainings globally. As such, there is a demand for strategies on how to train and implement these services to attain adequate quality. This study aims to evaluate the added value of a competency-driven approach to training of facilitators for a group intervention for children with severe emotional distress in Lebanon. METHODS: In a controlled before and after study, 24 trainees were randomly allocated to participate in either a competency-driven training (CDT) or training-as-usual (TAU) (1 : 1) for a psychological intervention for children with severe emotional distress. We assessed the change in demonstrated competencies, using standardised role-plays, before and after the training. Measures included the 13-item Working with children-Assessment of Competencies Tool (WeACT), the 15-item ENhancing Assessment of Common Therapeutic factors (ENACT) and the 6-item Group facilitation: Assessment of Competencies Tool (GroupACT). The trainer in the experimental arm used pre-training and during training competency assessment scores to make real-time adjustment to training delivery. Due to COVID-19 pandemic restrictions, all activities were done remotely. RESULTS: CDT resulted in significantly better outcomes on increasing competencies on the WeACT (repeated measures analysis of variance; F(1, 22) = 6.49, p < 0.018) and on the GroupACT (Mann-Whitney U = 22, p < 0.003), though not statistically significant on the ENACT. There is no significant between-group difference on the reduction of harmful behaviours, mainly because both forms of training appear equally successful in eliminating such behaviours. CONCLUSIONS: This proof-of-concept study demonstrates the potential of CDT, using standardised assessment of trainee competencies, to contribute to better training outcomes without extending the duration of training. CDT can result in up to 18% greater increase in adequate competency, when compared to TAU. The study also yields recommendations for further enhancing the benefits of competency-driven strategies. A fully powered trial is needed to confirm these findings.

Genetic testing in adult survivors of retinoblastoma in Denmark: A study of the experience and impact of genetic testing many years after initial diagnosis.

BACKGROUND: Survivors with heritable retinoblastoma (RB) face a high risk for second primary cancer and RB in their children. Knowledge of heredity can support second cancer surveillance, convey reproductive options or early diagnosis of RB in their offspring. Currently, all newly diagnosed Danish patients with RB are offered genetic testing, as opposed to a minority of survivors diagnosed before available DNA testing. OBJECTIVE: To examine RB survivors' response to unsolicited contact, uptake of genetic testing, and RB1 variant detection rate, and to qualitatively evaluate the experience and overall impact of genetic testing for heritable RB. METHODS: Genetically untested adult RB survivors were invited to receive genetic counseling, undergo genetic testing for heritable RB and complete an eye examination. The number of responses, uptake of genetic testing and genetic results are descriptively reported. Additionally, responding survivors participated in a qualitative interview study of the perceived impact of genetic testing. Interviews were audio-recorded, transcribed verbatim and thematically analyzed. RESULTS: Among invited RB survivors, 58% responded. Of these, 88% opted for genetic counseling and genetic testing. A diagnosis of heritable RB was established in 23% of RB survivors. Interestingly, all of these survivors were unilaterally affected. Analysis of data from the interviews revealed three recurring themes regarding the impact of genetic counseling and testing several years after initial diagnosis: 'Risk of what?', 'Knowledge is important' and 'Impact of the result'. The possible risk ofsecond cancer and RB in their children was new knowledge for several participants; however, in general, the participants appreciated receiving genetic information and certainty about heredity. Accordingly, the impact of genetic counseling and testing was perceived in a positive way. CONCLUSION: Overall, RB survivors valued the opportunity to receive genetic counseling and undergo genetic testing many years after diagnosis. Responding RB survivors appreciated the invitation to test, felt well-informed and described little decisional conflict regarding their decision-making, valuing the genetic information and certainty. Heritable RB was confirmed in 23% of the previously untested RB survivors. These individuals emphasized the value of knowing and being proactive regarding both reproduction and cancer risk.

Living with heritable retinoblastoma and the perceived role of regular follow-up at a retinoblastoma survivorship clinic: 'That is exactly what I have been missing'.

OBJECTIVE: To explore living with heritable retinoblastoma, specifically survivors' perceived role of regular follow-up at a retinoblastoma survivorship clinic. METHODS AND ANALYSIS: Adult survivors of heritable retinoblastoma were recruited from the Retinoblastoma Survivorship Clinic, Aarhus University Hospital. Ten survivors participated in individual explorative, semistructured interviews. Thematic data analysis was conducted. RESULTS: Five key themes relating to vision, social life, family, second cancer risk and the healthcare system were identified. Subthemes relating to the Retinoblastoma Survivorship Clinic included the retinoblastoma coordinator, cancer risk, psychosocial support and genetic knowledge. The retinoblastoma-related physical and psychosocial issues influenced survivors' everyday living; however, the opportunity to live a normal life varied considerably, with the majority experiencing no major limitations. The need for specialised management and a coordinator was emphasised to be the main value of the Retinoblastoma Survivorship Clinic. CONCLUSION: Despite reporting an overall normal life and no major limitations in daily living activities, our data confirm that heritable retinoblastoma impacts several aspects of daily living. Uniquely, this study demonstrates that the main value of the Retinoblastoma Survivorship Clinic was a specialised contact person and coordinator in the healthcare system, providing continuous and necessary management and guidance after retinoblastoma treatment, and for all aspects of health related to heritable retinoblastoma. The needs of heritable retinoblastoma survivors are complex and extensive, and the specific role of the healthcare system to support survivorship should be prioritised, specialised and multidisciplinary.

Incidence and Mortality of Second Primary Cancers in Danish Patients With Retinoblastoma, 1943-2013.

Importance: In heritable retinoblastoma, there is a significantly increased risk of second primary cancers (SPCs). Improved knowledge about the incidence and influence of heritability and treatment is important during therapy for patients with retinoblastoma. Objective: To assess the incidence of SPC in patients diagnosed with retinoblastoma in Denmark from 1943 to 2013 with a focus on heritability and the association of external radiotherapy with mortality. Design, Setting, and Participants: In this retrospective cohort study, data were extracted from the Danish Ocular Oncology Group Database containing complete data on all patients diagnosed with retinoblastoma , and obtained from the Danish Cancer Registry, which includes information on all patients with cancer from 1943 to December 31, 2013. Data analysis was conducted from December 1, 2017, to October 1, 2019. Data on 323 patients were included. Exposures: Heritability and retinoblastoma treatment. Main Outcomes and Measures: Standardized incidence rate, excess absolute risk, cumulative incidence of SPC, and mortality from SPC. Association of heritability and treatment with outcomes was estimated. Results: Of the 323 patients included in the analysis, 181 were men (56%), 133 had heritable retinoblastoma (41%), and 190 had nonheritable retinoblastoma (59%). The median age at diagnosis of SPC was 32.4 (interquartile range, 15.4-43.9) years in patients with heritable retinoblastoma and 38.6 (interquartile range, 20.5-49.4) years in those with nonheritable retinoblastoma. Twenty-five SPCs were identified in patients with heritable retinoblastoma vs 14 in patients with nonheritable retinoblastoma. Standardized incidence rate (SIR) of SPC in patients with heritable retinoblastoma was 11.39 (95% CI, 7.37-16.81) with an excess absolute risk of 70 cases per 10 000 person-years; the highest SIRs were for sarcoma (181.13; 95% CI, 98.94-303.92) and malignant melanoma (26.78; 95% CI, 9.78-58.30). The SIR for SPC in patients with nonheritable retinoblastoma was 1.52 (95% CI, 0.81-2.60). The cumulative incidence of SPCs at age 60 years was significantly higher in patients with heritable retinoblastoma (51%) compared with those with nonheritable retinoblastoma (13%) (P < .001) (hazard ratio, 5.0; 95% CI, 2.5-10.3). No significant differences were identified in overall risk of SPC in patients with heritable retinoblastoma treated with 3 different modalities: external radiotherapy, plaque (but no external) radiotherapy, and enucleation only, but an increased proportion of sarcomas was noted in the irradiated field. Mortality due to SPC was also higher in survivors of heritable retinoblastoma compared with those with nonheritable retinoblastoma (cumulative mortality, 34% vs 12% at age 60 years; P = .03). Conclusions and Relevance: The findings of this study suggest that the incidence and mortality associated with SPC were significantly higher in patients with heritable retinoblastoma vs patients with nonheritable retinoblastoma. The largest increases in risk were noted for sarcoma and malignant melanoma. External radiotherapy did not appear to increase the risk. These findings are relevant when treating patients with retinoblastoma to manage the risk for SPC.

Danish retinoblastoma patients 1943-2013 - genetic testing and clinical implications.

BACKGROUND: In heritable retinoblastoma there is a 50% risk of transmitting the RB1 mutation, and offspring carriers have more than 90% risk of developing retinoblastoma. Today, all newly diagnosed retinoblastoma patients in Denmark are screened for mutations in RB1, as opposed to only a minority of patients diagnosed before DNA testing was offered. Knowledge of heredity increases the chance of early diagnosis in offspring, leading to improved prognosis. We present data from the Danish retinoblastoma patients that emphasize the need for genetic counseling and RB1 screening in all untested retinoblastoma survivors. MATERIAL AND METHODS: Data are extracted from The Danish Ocular Oncology Group Database, a national population database containing data on all Danish retinoblastoma patients since 1943. RESULTS: In total 323 retinoblastoma patients have been diagnosed between 1943 and 2013. Since 1963, the rate has been stable around 1 per 14 000 live births with 95% of the patients surviving their retinoblastoma. Stratifying data on the time of diagnosis and status of genetic testing, the number of screened patients gradually increased from 5% in the beginning of the period to 96% in the last five-year period. A cohort of 181 retinoblastoma survivors with sporadic disease (15% heritable) did not receive genetic testing. Since the introduction of routine testing, one of 14 sporadic unilateral patients tested (7%) has been identified with a germline mutation. Before routine testing, five additional sporadic unilateral patients have been identified as heritable. CONCLUSION: Only a minority of Danish retinoblastoma patients diagnosed before routine genetic testing was offered have been RB1 screened. To counsel the remaining untested patients and their families sufficiently regarding the risk to offspring and elevated risk of second primary cancers, we recommend information and access to genetic counseling and RB1 screening. This has ethical, psychological and possible economic consequences, and should be handled with caution.

Cardiac magnetic resonance and electroanatomical mapping of acute and chronic atrial ablation injury: a histological validation study.

AIMS: To provide a comprehensive histopathological validation of cardiac magnetic resonance (CMR) and endocardial voltage mapping of acute and chronic atrial ablation injury. METHODS AND RESULTS: 16 pigs underwent pre-ablation T2-weighted (T2W) and late gadolinium enhancement (LGE) CMR and high-density voltage mapping of the right atrium (RA) and both were repeated after intercaval linear radiofrequency ablation. Eight pigs were sacrificed following the procedure for pathological examination. A further eight pigs were recovered for 8 weeks, before chronic CMR, repeat RA voltage mapping and pathological examination. Signal intensity (SI) thresholds from 0 to 15 SD above a reference SI were used to segment the RA in CMR images and segmentations compared with real lesion volumes. The SI thresholds that best approximated histological volumes were 2.3 SD for LGE post-ablation, 14.5 SD for T2W post-ablation and 3.3 SD for LGE chronically. T2-weighted chronically always underestimated lesion volume. Acute histology showed transmural injury with coagulative necrosis. Chronic histology showed transmural fibrous scar. The mean voltage at the centre of the ablation line was 3.3 mV pre-ablation, 0.6 mV immediately post-ablation, and 0.3 mV chronically. CONCLUSION: This study presents the first histopathological validation of CMR and endocardial voltage mapping to define acute and chronic atrial ablation injury, including SI thresholds that best match histological lesion volumes. An understanding of these thresholds may allow a more informed assessment of the underlying atrial substrate immediately after ablation and before repeat catheter ablation for atrial arrhythmias.

Interactive 3D computer model of the human corneolimbal region: crypts, projections and stem cells.

PURPOSE: This study aims to clarify the existence of and to map the localization of different proposed stem cell niches in the corneal limbal region. MATERIALS AND METHODS: One human eye was cut into 2200 consecutive sections. Every other section was stained with haematoxylin and eosin, digitized at low and high magnification, aligned, 3D reconstructed and visualized using interactive 3D visualization software. The visualization software has interactive tools that make free rotations in all directions possible and makes it possible to create virtual sections independent of the original cutting plan. In all, one low-magnification and 24 high-magnification interactive 3D models were created. Immunohistochemistry against stem cell markers p63 and ΔNp63α was performed as a supplement to the 3D models. RESULTS: Using the interactive 3D models, we identified three types of stem cell niches in the limbal region: limbal epithelial crypts (LECs), limbal crypts (LCs) and focal stromal projections (FSPs). In all, eight LECs, 25 LCs and 105 FSPs were identified in the limbal region. The LECs, LCs and FSPs were predominantly located in the superior limbal region with seven LECs, 19 LCs and 93 FSPs in the superior limbal region and one LEC, six LCs and 12 FSPs in the inferior limbal region. Only few LECs, LCs and FSPs were localized nasally and temporally. CONCLUSION: Interactive 3D models are a powerful tool that may help to shed more light on the existence and spatial localization of the different stem cell niches (LECs, LCs and FSPs) in the corneal limbal region.

CMR assessment of endothelial damage and angiogenesis in porcine coronary arteries using gadofosveset.

BACKGROUND: Endothelial damage and angiogenesis are essential for atherosclerotic plaque development and destabilization. We sought to examine whether contrast enhanced cardiovascular magnetic resonance (CMR) using gadofosveset could show endothelial damage and neovessel formation in balloon injured porcine coronary arteries. METHODS AND RESULTS: Data were obtained from seven pigs that all underwent balloon injury of the left anterior descending coronary artery (LAD) to induce endothelial damage and angiogenesis. Between one - 12 days (average four) after balloon injury, in vivo and ex vivo T1-weighted coronary CMR was performed after intravenous injection of gadofosveset. Post contrast, CMR showed contrast enhancement of the coronary arteries with a selective and time-dependent average expansion of the injured LAD segment area of 45% (p = 0.04; CI95 = [15%-75%]), indicating local extravasation of gadofosveset. Vascular and perivascular extravasation of albumin (marker of endothelial leakiness) and gadofosveset was demonstrated with agreement between Evans blue staining and ex vivo CMR contrast enhancement (p = 0.026). Coronary MRI contrast enhancement and local microvessel density determined by microscopic examination correlated (ρ = 0.82, p < 0.001). CONCLUSION: Contrast enhanced coronary CMR with gadofosveset can detect experimentally induced endothelial damage and angiogenesis in the porcine coronary artery wall.

Accelerated 3D catheter visualization from triplanar MR projection images.

One major obstacle for MR-guided catheterizations is long acquisition times associated with visualizing interventional devices. Therefore, most techniques presented hitherto rely on single-plane imaging to visualize the catheter. Recently, accelerated three-dimensional (3D) imaging based on compressed sensing has been proposed to reduce acquisition times. However, frame rates with this technique remain low, and the 3D reconstruction problem yields a considerable computational load. In X-ray angiography, it is well understood that the shape of interventional devices can be derived in 3D space from a limited number of projection images. In this work, this fact is exploited to develop a method for 3D visualization of active catheters from multiplanar two-dimensional (2D) projection MR images. This is favorable to 3D MRI as the overall number of acquired profiles, and consequently the acquisition time, is reduced. To further reduce measurement times, compressed sensing is employed. Furthermore, a novel single-channel catheter design is presented that combines a solenoidal tip coil in series with a single-loop antenna, enabling simultaneous tip tracking and shape visualization. The tracked tip and catheter properties provide constraints for compressed sensing reconstruction and subsequent 2D/3D curve fitting. The feasibility of the method is demonstrated in phantoms and in an in vivo pig experiment.

High-resolution ex vivo magnetic resonance angiography: a feasibility study on biological and medical tissues.

BACKGROUND: In biomedical sciences, ex vivo angiography is a practical mean to elucidate vascular structures three-dimensionally with simultaneous estimation of intravascular volume. The objectives of this study were to develop a magnetic resonance (MR) method for ex vivo angiography and to compare the findings with computed tomography (CT). To demonstrate the usefulness of this method, examples are provided from four different tissues and species: the human placenta, a rice field eel, a porcine heart and a turtle. RESULTS: The optimal solution for ex vivo MR angiography (MRA) was a compound containing gelatine (0.05 g/mL), the CT contrast agent barium sulphate (0.43 mol/L) and the MR contrast agent gadoteric acid (2.5 mmol/L). It was possible to perform angiography on all specimens. We found that ex vivo MRA could only be performed on fresh tissue because formalin fixation makes the blood vessels permeable to the MR contrast agent. CONCLUSIONS: Ex vivo MRA provides high-resolution images of fresh tissue and delineates fine structures that we were unable to visualise by CT. We found that MRA provided detailed information similar to or better than conventional CTA in its ability to visualize vessel configuration while avoiding interfering signals from adjacent bones. Interestingly, we found that vascular tissue becomes leaky when formalin-fixed, leading to increased permeability and extravascular leakage of MR contrast agent.

Visual outcome, local tumour control, and eye preservation after 106Ru/Rh brachytherapy for choroidal melanoma.

To study the visual outcome, local tumour control, and eye preservation 5 years after ruthenium/rhodium 106 brachytherapy for choroidal melanoma. The study included 55 consecutive patients treated by 106Ru/Rh brachytherapy for a choroidal melanoma during the period 1988-2000 and followed through 2004. The 5-year probability for not losing at least 5 Snellen lines was 59% (n = 45), for retaining a visual acuity of 0.33 or better was 28% (n = 34), and for retaining better than 0.1 was 40% (n = 45). The 5-year probability for no local recurrence was 73% and for eye preservation 72% (n = 55). 106Ru/Rh brachytherapy for choroidal melanoma resulted in a clinically significant vision loss, no local recurrence, and eye preservation in most patients after 5 years. 106Ru/Rh brachytherapy can be regarded as a good treatment option for small and medium-sized tumours but not for large tumours.

Upgrading of existing sludge treatment processes for phosphorus management serving a EBPR WWTP.

For a large-scale wastewater treatment plant to comply with phosphorus consents using enhanced biological phosphorus removal processes, its sludge and liquor treatment processes need to be carefully upgraded. In this case study, the wastewater treatment plant of interest has three different types of sludge treated by two different and independent sludge treatment processes. The task of upgrading the sludge treatment systems to serve an EBPR process while satisfying other regulatory and operational constraints in a cost effective way presents an interesting challenge. A range of process options was investigated to include P-rich surplus activated sludge treatment, raw sludge treatment, and sludge liquors treatment. Sludge pre-liming, i.e. to introduce lime slurry into raw liquid sludge before the dewatering stage, was studied in bench-scale and full-scale trials for phosphorus precipitation and pathogen reduction. It was applied to the mixture of surplus activated sludge and imported sludge. The results showed that a complete phosphorus precipitation was achieved at above pH 9 with lime addition of 7% (w/w as calcium hydroxide to sludge dry weight). A satisfactory 2-log pathogen reduction was consistently achieved at above pH 11 with lime addition of 14% (w/w). The process significantly simplified the potential upgrading work for sludge and liquor treatment, compared to other alternatives.

Key influential factors for sludge pre-fermentation process design--a case study.

Sewage sludge pre-fermentation process produces readily biodegradable carbon, which is essential for reliable biological phosphorus removal and efficient denitrification. This bench scale study was to develop site-specific design parameters for a sludge fermentation process, and to look into the effects of various influential factors. The key factors investigated induded solids retention time (4-8 days), temperature (9-19 degrees C) and sludge concentrations (0.5%-4% DS). The optimum Volatile Fatty Adds yield was found at a sludge concentration of 1%-1.5% DS. A solid retention time of 4 days at 15-20 degrees C was found to be most cost effective. The fermentation reaction was temperature sensitive, which was found to be inefficient at temperature below 12-15 degrees C. Under the optimum conditions, 80-100 mgVFA g(-1) VSS can be generated from fermentation process, which will result in an increase of 20-24 mg l(-1) in the settled sewage based on average flow. A significant pathogen reduction level was also demonstrated over the fermentation period. Liquid sludge from the small rural wastewater treatment plants is often imported to a regional sludge treatment centre for more advanced treatment to comply with the Regulations. The suitability of this imported sludge for pre-fermentation process was also investigated in this study.

Induction and impairment of saturated yaw and surge vection.

A flight simulator was used to investigate the perception of self-motion and visual scene motion during the induction of saturated 10 deg/sec yaw and 50 m/sec surge vection, and during subsequent impairment of saturated vection by inertial motions. The subjects (n = 5) did not perceive any self-acceleration or visual scene deceleration during the induction of saturated vection but perceived a rather sudden change in self-velocity and visual scene velocity. The mean group times to saturated vection were 3.0 sec for yaw and 2.7 sec for surge. Above certain inertial motion amplitudes, the subjects reported additional self-motion from the applied inertial motions while experiencing saturated vection. To impair saturated yaw vection, these amplitudes were 0.6 m/sec2, 0.4 m/sec2, 8 deg/sec2, and 5 deg/sec2, for surge, sway, roll and yaw motions, respectively. To impair saturated surge vection, these amplitudes were 0.6 m/sec2, 0.3 m/sec2, 5 deg/sec2, and 4 deg/sec2, respectively. The results indicate that saturated vection is more robust for translations than for rotations because the rotational inertial amplitudes were closer to the amplitudes at which the applied inertial motion was perceived than the translational inertial amplitudes.

An earth-stationary perceived visual scene during roll and yaw motions in a flight simulator.

A flight simulator was used for two experiments to determine the amplitude combinations of visual scene motion (with respect to the observer) and inertial body motion (with respect to an earth-fixed frame) that provide the perception of an earth-stationary visual scene and realistic simulated self-motion. In the first experiment, this range was determined for simulated self-motion about the longitudinal body axis, while in the second, self-motion about the vertical body axis was considered. Both the inertial and the visual motions consisted of 0.75 a accelerations, followed by 1.50 s decelerations, and 0.75 s accelerations. The visual scene acceleration amplitude, W, was fixed at either 0, 2, 4, 8, or 12 degrees/s2 while the inertial acceleration amplitude, I, was varied by a staircase procedure. Following the visual and inertial motions, the subjects pushed a button when they perceived the scene to be not earth-stationary. At each visual scene acceleration amplitude, the lower and upper inertial threshold amplitudes were determined, which bounded the range in which the visual scene was perceived to be earth-stationary. The lower and upper inertial thresholds were defined as the inertial motion amplitudes for which the inertial stimulations were too small or too large, respectively, to provide the perception of an earth-stationary visual scene. The lower inertial thresholds were determined for W = 2 through W = 12 degrees/s2 and were found to be well approximated by the linear relation I = -0.37 + 0.60 W for the roll motions tested, and I = 1.1 + 0.33 W for the yaw motions tested. The upper inertial thresholds were determined for W = 0 through W = 12 degrees/s2 and were found to be well approximated by the linear relation I = 2.7 + 1.7 W for roll and I = 2.2 + 1.4 W for yaw. With the assumption that the lower and upper inertial threshold amplitudes are symmetric about the W = 0 condition, the present results infer a strong nonlinearity of the thresholds near W = 0.

Simulating self-motion.

In general, vehicle motions far exceed the mechanical constraints of an earth-fixed simulator base. Inertial motions can, therefore, only be simulated in partial agreement with those of the actual vehicle. As a consequence, physical mismatches between inertial and environmental motion are inevitable. Here, the concept of a subjective reference frame is introduced, relative to which perceived self-motion is defined. This frame must be released from the earth-fixed frame to evoke simulated self-motion. In addition, self-motion and environmental motion need to be perceived reciprocal, in order to evoke a stationary perceived environment. Due to the only limited accuracy of human self-motion perception, however, perceived self-motion and perceived environmental motion need not to be exactly reciprocal. The extent to which self-motion and environmental motion may differ can be expressed by a just noticeable difference. This just noticeable difference denotes the threshold at which the environment is perceived to move. In this article, a self-motion perception model is outlined in which perceived environmental motion and perceived self-motion are separated. The perception model and the just noticeable differences can then be applied to determine the inertial stimulation that is needed to evoke perceived self-motion, in which the environment is perceived stationary throughout simulation.