Identifikasi Genangan Banjir di Wilayah DKI Jakarta Menggunakan Citra Satelit Sentinel-1

Provinsi DKI Jakarta merupakan wilayah dengan karakteristik topografi yang berada pada kemiringan lereng relatif landai dan terletak pada dataran rendah. Hal ini menyebabkan wilayah Jakarta menjadi semakin rentan tergenang air dan banjir pada musim hujan. Pada awal tahun 2020, Jakarta mengalami banjir yang diakibatkan oleh hujan lebat yang turun sejak 31 Desember 2019 hingga 1 Januari 2020. Untuk keperluan antisipasi dan mitigasi bencana terkait banjir tersebut diperlukan ketersediaan data tentang luas genangan banjir dan letaknya secara cepat. Salah satu teknologi yang potensial untuk diterapkan adalah menggunakan citra satelit Sentinel-1. Berdasarkan kondisi tersebut, telah dilakukan kajian untuk mendeteksi daerah terdampak genangan banjir dari citra satelit Sentinel-1. Adapun teknik yang digunakan adalah metode change detection dan thresholding. Pada kajian ini digunakan citra Sentinel-1 perekaman tahun 2019 dan 2020, DEMNAS, Global Surface Water dan batas administrasi wilayah DKI Jakarta. Adapun tahapan pelaksanaan kajian mencakup proses change detection dengan ratio image dari dua citra Sentinel-1 GRD sebelum dan saat banjir, perhitungan nilai optimum threshold untuk menentukan banjir dan tidak banjir, masking banjir, dan perhitungan luas genangan. Berdasarkan hasil kajian diperoleh luas total daerah yang terkena banjir sekitar 1.156,84 hektar, sedangkan luas area banjir dari data Pemprov DKI sekitar 12.896,35 hektar. Hasil validasi menggunakan data Pemprov DKI dengan membandingan antara citra Sentinel-1 tahun 2019 dan 2020, diperoleh hasil 61 lokasi atau sekitar 28,96% termasuk ke dalam hasil interpretasi kelas banjir dan terdapat 157 lokasi atau sekitar 71,04% termasuk ke dalam hasil interpretasi kelas tidak banjir.

Pericoronary adipose tissue attenuation, low-attenuation plaque burden and 5-year risk of myocardial infarction

Introduction Pericoronary adipose tissue (PCAT) attenuation has emerged as a surrogate marker of pericoronary inflammation. To date, no studies have compared the impact of pericoronary adipose tissue (PCAT) attenuation and quantitative plaque burden on cardiac outcomes. Purpose We aimed to establish the relative merits of these approaches to risk prediction and hypothesised that the combination of PCAT attenuation and quantitative plaque burden measures could provide additive and improved prediction of myocardial infarction in patients with stable chest pain. Methods In a post-hoc analysis of a randomized controlled trial, we investigated the association between the future risk of fatal or non-fatal myocardial infarction and PCAT attenuation measured from CT coronary angiography using multivariable Cox regression models including plaque burden, obstructive coronary disease and cardiac risk score (incorporating age, sex, diabetes, smoking, hypertension, hyperlipidaemia and family history of cardiovascular disease). Results In 1697 evaluable participants (mean age 58±10 years), there were 37 myocardial infarctions after a median follow-up of 4.7 [interquartile interval, 4.0–5.7] years. Median low-attenuation plaque burden was 4.20 [0–6.86] % and mean PCAT −76±8 Hounsfield units (HU). PCAT attenuation of the right coronary artery (RCA) was predictive of myocardial infarction (hazard ratio [HR] 1.55, 95% CI 1.08–2.22; p=0.017, per 1 standard deviation increment) with an optimum threshold of −70.5 HU [Hazards ratio (HR) 2.45, 95% CI 1.2–4.9; p=0.01]. Univariable analysis also identified the burden of non-calcified, low-attenuation and calcified plaque as well as Agatston coronary calcium score, presence of obstructive coronary artery disease and cardiovascular risk score were predictors of myocardial infarction (Figure 1). In multivariable analysis, only the low-attenuation plaque burden (HR 1.80, 95% CI 1.16 to 2.81, p=0.011, per doubling) and PCAT-RCA (HR 1.47 95%1.02 to 2.13, p=0.040, per standard deviation increment) remained predictors of myocardial infarction (Figure 1). In multivariable analysis, adding PCAT-RCA ≥-70.5 HU to low-attenuation plaque burden >4% (optimum threshold for future myocardial infarction; HR = 4.87, 95% CI 2.03–11.78; p<0.0001) led to improved prediction of future myocardial infarction (HR 11.7, 95% CI 3.3–40.9; p<0.0001); Figure 2. In ROC analysis, integration of PCAT-RCA attenuation and LAP burden, increased the prediction for myocardial infarction compared to LAP alone (ΔAUC=0.04; p=0.01). Conclusion CT coronary angiography defined PCAT attenuation and low-attenuation plaque have marked and additive predictive value for the risk of fatal or non-fatal myocardial infarction. FUNDunding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The Chief Scientist Office of the Scottish Government Health and Social Care Directorates, British Heart Foundation, National Institute of Health/National Heart, Lung, and Blood Institute grant

A Fractal Approach to Urban Boundary Delineation Based on Raster Land Use Maps: A Case of Shanghai, China

Given the diverse socioecological consequences of rapid urban sprawl worldwide, the delineation and monitoring of urban boundaries have been widely used by local governments as a planning instrument for promoting sustainable development. This study demonstrates a fractal method to delineate urban boundaries based on raster land use maps. The basic logic is that the number of built-up land clusters and their size at each dilation step follows a power-law function. It is assumed that two spatial subsets with distinct fractal characteristics would be obtained when the deviation between the dilation curve and a straight line reaches the top point. The top point is regarded to be the optimum threshold for classifying the built-up land patches, because the fractality of built-up land would no longer exist beyond the threshold. After that, all the built-up land patches are buffered with the optimum threshold and the rank-size distribution of new clusters can be re-plotted. Instead of artificial judgement, hierarchical agglomerative clustering is utilized to automatically classify the urban and rural clusters. The approach was applied to the case of Shanghai, the most rapidly urbanizing megacity in China, and the dynamic changes of the urban boundaries from 1994 to 2016 were analyzed. On this basis, urban–rural differences were further explored through several fractal or nonfractal indices. The results show that the proposed fractal approach can accurately distinguish the urban boundary without subjective choice of thresholds. Extraordinarily different fractal dimensions, aggregation and density and similar average compactness were further identified between built-up land in urban and rural areas. The dynamic changes in the urban boundary indicated rapid urban sprawl within Shanghai during the study period. In view of the popularization and global availability of raster land use maps, this paper adds fuels to the cutting-edge topic of distinguishing the morphological criteria to universally describe urban boundaries.

Fighting cancer with oncolytic viral therapy: identifying threshold parameters for success

We model interactions between cancer cells and free virus during oncolytic viral therapy. One of our main goals is to identify parameter regions which yield treatment failure or success. We show that the tumor size under therapy at a certain time is less than the tumor size without therapy. We determine the minimum tumor size by the therapy and parameter regions under which this minimum is attained. Our analysis shows there are two thresholds for the horizontal transmission rate: a "Control threshold", the threshold above which treatment is efficient, and an "optimum threshold'', the threshold beyond which infection prevalence reaches 100% and the tumor shrinks to its smallest size. Moreover, we explain how changes in the virulence level of the free virus alters the optimum threshold and the minimum tumor size. We identify a threshold for the virulence level of the virus and show how this threshold depends on timescale of virus dynamics. Our results suggests that when timescale of virus dynamics is fast, administration of a more virulent virus leads into more tumor reduction. When viral timescale is slow, a higher virulence will have drawbacks on the results, such as high amplitude oscillations. Furthermore, our numerical observation depicts fast and slow dynamics. Our numerical simulations indicate there exists a two-dimensional globally attracting surface that includes unstable manifold of the interior equilibrium. All solutions with positive initial conditions rapidly approach this two-dimensional attracting surface. In contrast, the trajectories on the attracting surface slowly tend to the periodic solution.

Simplified intraoperative parathormone assay for primary hyperparathyroidism in a resource-limited setting

Background: The optimum threshold of IOPTH decay remains a debate and numerous criteria have been described. In this study, we utilize a single-sample IOPTH taken 10 min post excision. Materials & methods: This 4-year query of a prospectively maintained database included primary hyperparathyroidism patients with pre-operative PTH done 1 week prior to surgery, and a 10-min post excision IOPTH value. Optimal cut-off for PTH and sensitivity/specificity were calculated. Results: A total of 93 patients had single-gland disease, of whom 79 (84.9%) were symptomatic. The 10-min post excision assay sensitivity in single-gland disease was 97.8% (50% fall), 95% (60% fall) and 83.9% (70% fall). Conclusion: A post excision single-shot IOPTH assay with a 50% fall offers a sensitivity of 97.8% in patients of primary hyperparathyroidism with single-gland benign disease.

Appropriate thresholds for accurate screening for β-thalassemias in the newborn period: results from a French center for newborn screening

ObjectivesNewborn screening (NBS) for β-thalassemia is based on measuring the expression of the hemoglobin A (HbA) fraction. An absence or very low level of HbA at birth may indicate β-thalassemia. The difficulty is that the HbA fraction at birth is correlated with gestational age (GA) and highly variable between individuals. We used HbA expressed in multiples of the normal (MoM) to evaluate relevant thresholds for NBS of β-thalassemia.MethodsThe chosen threshold (HbA≤0.25 MoM) was prospectively applied for 32 months in our regional NBS program for sickle cell disease, for all tests performed, to identify patients at risk of β-thalassemia. Reliability of this threshold was evaluated at the end of the study.ResultsIn all, 343,036 newborns were tested, and 84 suspected cases of β-thalassemia were detected by applying the threshold of HbA≤0.25 MoM. Among the n=64 cases with confirmatory tests, 14 were confirmed using molecular analysis as β-thalassemia diseases, 37 were confirmed as β-thalassemia trait and 13 were false-positive. Determination of the optimum threshold for β-thalassemia screening showed that HbA≤0.16 MoM had a sensitivity of 100% and a specificity of 95.3%, whatever the GA.ConclusionsNBS for β-thalassemia diseases is effective, regardless of the birth term, using the single robust threshold of HbA≤0.16 MoM. A higher threshold would also allow screening for carriers, which could be interesting when β-thalassemia constitutes a public health problem.

Prognostic Threshold for Circulating Tumor Cells in Patients With Pancreatic and Midgut Neuroendocrine Tumors

Background Circulating tumor cells (CTCs) are detectable in patients with neuroendocrine tumors (NETs) and are accurate prognostic markers although the optimum threshold has not been defined. Objective This work aims to define optimal prognostic CTC thresholds in PanNET and midgut NETs. Patients and Methods CellSearch was used to enumerate CTCs in 199 patients with metastatic pancreatic (PanNET) (90) or midgut NETs (109). Patients were followed for progression-free survival (PFS) and overall survival (OS) for a minimum of 3 years or until death. Results The area under the receiver operating characteristic curve (AUROC) for progression at 12 months in PanNETs and midgut NETs identified the optimal CTC threshold as 1 or greater and 2 or greater, respectively. In multivariate logistic regression analysis, these thresholds were predictive for 12-month progression with an odds ratio (OR) of 6.69 (P < .01) for PanNETs and 5.88 (P < .003) for midgut NETs. The same thresholds were found to be optimal for predicting death at 36 months, with an OR of 2.87 (P < .03) and 5.09 (P < .005) for PanNETs and midgut NETs, respectively. In multivariate Cox hazard regression analysis for PFS in PanNETs, 1 or greater CTC had a hazard ratio (HR) of 2.6 (P < .01), whereas 2 or greater CTCs had an HR of 2.25 (P < .01) in midgut NETs. In multivariate analysis OS in PanNETs, 1 or greater CTCs had an HR of 3.16 (P < .01) and in midgut NETs, 2 or greater CTCs had an HR of 1.73 (P < .06). Conclusions The optimal CTC threshold to predict PFS and OS in metastatic PanNETs and midgut NETs is 1 and 2, respectively. These thresholds can be used to stratify patients in clinical practice and clinical trials.

Optimum Threshold Minimizes Noise in Timing of Intracellular Events

ABSTRACTHow the noisy expression of regulatory proteins affects timing of intracellular events is an intriguing fundamental problem that influences diverse cellular processes. Here we use the bacteriophage λ to study event timing in individual cells where cell lysis is the result of expression and accumulation of a single protein (holin) in the Escherchia coli cell membrane up to a critical threshold level. Site-directed mutagenesis of the holin gene was used to generate phage variants that vary in their timing of lysis from 30 to 190 min. Observation of the lysis times of single cells reveals an intriguing finding – the noise in lysis timing first decreases with increasing lysis time to reach a minimum, and then sharply increases at longer longer lysis times. A mathematical model with stochastic expression of holin together with dilution from cell growth was sufficient to explain the non-monotonic noise profile, and identify holin accumulation thresholds that generate precision in lysis timing.

Improved characterisation of MRSA transmission using within-host bacterial sequence diversity

Methicillin-resistant Staphylococcus aureus (MRSA) transmission in the hospital setting has been a frequent subject of investigation using bacterial genomes, but previous approaches have not yet fully utilised the extra deductive power provided when multiple pathogen samples are acquired from each host. Here, we used a large dataset of MRSA sequences from multiply-sampled patients to reconstruct colonisation of individuals in a high-transmission setting in a hospital in Thailand. We reconstructed transmission trees for MRSA. We also investigated transmission between anatomical sites on the same individual, finding that this either occurs repeatedly or involves a wide transmission bottleneck. We examined the between-subject bottleneck, finding considerable variation in the amount of diversity transmitted. Finally, we compared our approach to the simpler method of identifying transmission pairs using single nucleotide polymorphism (SNP) counts. This suggested that the optimum threshold for identifying a pair is 39 SNPs, if sensitivities and specificities are equally weighted.