Null Geodesics from Ladder Molecules

We propose a discrete analogue of null geodesics in causal sets that are approximated by a region of 2d Minkowski spacetime, in the spirit of Kronheimer and Penrose's "grids" and "beams" for an abstract causal space. The causal set analogues are "ladder molecules", whose rungs are linked pairs of elements corresponding loosely to Barton et al's horizon bi-atoms. In 2d a ladder molecule traps a ribbon of null geodesics corresponding to a thickened or fuzzed out horizon. The existence of a ladder between linked pairs of elements in turn provides a generalisation of the horismotic relation to causal sets. Simulations of causal sets approximated by a region of 2d Minkowski spacetime show that ladder molecules are fairly dense in the causal set, and provide a light-cone like grid. Moreover, similar to the uniqueness of null geodesics between horismotically related events in the spacetime, in such causal sets there is a unique ladder molecule between any two linked pairs which are related by the generalised horismotic relation.Comment: Contribution to the collection "Singularity theorems, causality, and all that (SCRI21)" in the journal General Relativity and Gravitation, in honor of Roger Penros

The evaluation of safety and efficacy of percutaneous nephrostomy in young adult patients with severe hydronephrosis due to uretropelvic junction obstructions

Background: Majority of poorly functioning kidney (PFK) due to primary ureteropelvic junction obstructions (UPJO) in young adult have potential to recover after an attempted percutaneous nephrostomy (PCN). The split renal function measured by nuclear renal scan may not be sufficient enough to predict recovery of such kidney. Therefore, this study was undertaken to determine the functional recovery and potential salvageability of PFK due UPJO. Objective of the study was to evaluate safety and efficacy of PCN in adult patients with severe hydronephrosis due to PUJO.Methods: A total of 25 (10 male and 15 female) young adult patients of severe hydronephrosis due to PUJO and SRF<20% underwent PCN procedures. Only, those who had significant improvement in their SRF ≥10% and developed PCN output ≥400 ml/day underwent Anderson-Hyenas pyeloplasty and rest underwent nephrectomy.Results: Both male and female young patients had significantly improvement after 6 weeks of PCN, their mean pre-PCN SRF changed from 16.30% and 12.27% to became 28.10±08.41% and 18.53±09.89%, respectively. Those with age <30 years improved most with ≥10% increase in the mean SRF and in 72% patients average PCN output increased from 279.80±93.90 ml/day to 445.20±160.341 ml/day at 6 weeks period. Overall, the patients with average PCN output ≥400 ml/day had a mean improvement of 10.33±05.48% in SRF. However, 5(20%) developed haematuria, 8% fever, 16% displaced PCN tip with no major puncture site bleed.Conclusions: The trial of PCN before definite surgery in young adult patients with poorly functioning kidney due to UPJO not only predicts renal renal function recovery but also prevent unwarranted renal loss

Detection of Renal Vein and Inferior Vena Cava Thrombosis from Renal Cell Carcinoma by F-18 FDG PET/CT in Two Patients

 Tumour thrombosis is a relatively rare complication of solid cancers, with occult inferior vena cava(IVC) tumour thrombosis having a reported incidence rate of 0.11%. Renal cell carcinoma(RCC) has a propensity to extend as tumour thrombus into the renal vein and IVC. The preoperative assessment for the presence and extent of renal vein and IVC tumour thrombus is important for planning appropriate surgical resection. There are reports having described the diagnosis of tumour thrombosis by Fluorine-18 fluorodeoxyglucose positron emission tomography and Computed tomography (F-18 FDG PET/CT). We present two cases, one with right RCC showing renal vein and IVC tumour invasion and another left RCC with renal vein, IVC and hepatic vein thrombosis detected using FDG PET/CT

Detection of Renal Vein and Inferior Vena Cava Thrombosis from Renal Cell Carcinoma by F-18 FDG PET/CT in Two Patients

Tumour thrombosis is a relatively rare complication of solid cancers, with occult inferior vena cava(IVC) tumour thrombosis having a reported incidence rate of 0.11%. Renal cell carcinoma(RCC) has a propensity to extend as tumour thrombus into the renal vein and IVC. The preoperative assessment for the presence and extent of renal vein and IVC tumour thrombus is important for planning appropriate surgical resection. There are reports having described the diagnosis of tumour thrombosis by Fluorine-18 fluorodeoxyglucose positron emission tomography and Computed tomography (F-18 FDG PET/CT). We present two cases, one with right RCC showing renal vein and IVC tumour invasion and another left RCC with renal vein, IVC and hepatic vein thrombosis detected using FDG PET/CT

Carnegie Mellon Team Tartan: Mission-level Robustness with Rapidly Deployed Autonomous Aerial Vehicles in the MBZIRC 2020

For robotics systems to be used in high risk, real-world situations, they have to be quickly deployable and robust to environmental changes, under-performing hardware, and mission subtask failures. Robots are often designed to consider a single sequence of mission events, with complex algorithms lowering individual subtask failure rates under some critical constraints. Our approach is to leverage common techniques in vision and control and encode robustness into mission structure through outcome monitoring and recovery strategies, aided by a system infrastructure that allows for quick mission deployments under tight time constraints and no central communication. We also detail lessons in rapid field robotics development and testing. Systems were developed and evaluated through real-robot experiments at an outdoor test site in Pittsburgh, Pennsylvania, USA, as well as in the 2020 Mohamed Bin Zayed International Robotics Challenge. All competition trials were completed in fully autonomous mode without RTK-GPS. Our system led to 4th place in Challenge 2 and 7th place in the Grand Challenge, and achievements like popping five balloons (Challenge 1), successfully picking and placing a block (Challenge 2), and dispensing the most water autonomously with a UAV of all teams onto an outdoor, real fire (Challenge 3).Comment: 28 pages, 26 figures. To appear in Field Robotics, Special Issues on MBZIRC 202

EvDNeRF: Reconstructing Event Data with Dynamic Neural Radiance Fields

We present EvDNeRF, a pipeline for generating event data and training an event-based dynamic NeRF, for the purpose of faithfully reconstructing eventstreams on scenes with rigid and non-rigid deformations that may be too fast to capture with a standard camera. Event cameras register asynchronous per-pixel brightness changes at MHz rates with high dynamic range, making them ideal for observing fast motion with almost no motion blur. Neural radiance fields (NeRFs) offer visual-quality geometric-based learnable rendering, but prior work with events has only considered reconstruction of static scenes. Our EvDNeRF can predict eventstreams of dynamic scenes from a static or moving viewpoint between any desired timestamps, thereby allowing it to be used as an event-based simulator for a given scene. We show that by training on varied batch sizes of events, we can improve test-time predictions of events at fine time resolutions, outperforming baselines that pair standard dynamic NeRFs with event generators. We release our simulated and real datasets, as well as code for multi-view event-based data generation and the training and evaluation of EvDNeRF models (https://github.com/anish-bhattacharya/EvDNeRF).Comment: 16 pages, 20 figures, 2 table

FDG PET/CT in the Evaluation of Late Manifestation of Adrenal Metastasis after Radical Nephrectomy in Patients with Renal Cell Carcinoma: A Report of Four Cases and Review of Literature

 Purpose: Presence of distant metastasis is a strong independent predictor of poor survival in patients with renal cell carcinoma (RCC). Positron emission tomography using F-18 fluorodeoxyglucose (FDG) has been reported to be superior to conventional anatomic imaging modalities for detecting distant metastases from RCC.  Methods: The authors report the findings of four patients who underwent FDG positron emission tomography / computed tomography (PET/CT) at varying periods after radical nephrectomy for RCC.  Results: FDG PET/CT detected increased tracer concentration in the adrenal glands in all four patients and subsequent fine needle aspiration confirmed metastatic RCC. While the adrenal was the only site of metastasis in one patient, additional metastases were detected in lymph nodes and lungs in the others.  Conclusions: RCC metastatic to the adrenal gland is usually a vascular tumour and there is an intrinsic risk of haemorrhage during CT-guided needle biopsy. This small series of cases suggests that FDG PET/CT is a useful non-invasive investigation in identifying malignant adrenal lesions in patients with RCC presenting after nephrectomy