An Efficient Block Circulant Preconditioner For Simulating Fracture Using Large Fuse Networks

{\it Critical slowing down} associated with the iterative solvers close to the critical point often hinders large-scale numerical simulation of fracture using discrete lattice networks. This paper presents a block circlant preconditioner for iterative solvers for the simulation of progressive fracture in disordered, quasi-brittle materials using large discrete lattice networks. The average computational cost of the present alorithm per iteration is $O(rs log s) + delops$, where the stiffness matrix ${\bf A}$ is partioned into $r$-by-$r$ blocks such that each block is an $s$-by-$s$ matrix, and $delops$ represents the operational count associated with solving a block-diagonal matrix with $r$-by-$r$ dense matrix blocks. This algorithm using the block circulant preconditioner is faster than the Fourier accelerated preconditioned conjugate gradient (PCG) algorithm, and alleviates the {\it critical slowing down} that is especially severe close to the critical point. Numerical results using random resistor networks substantiate the efficiency of the present algorithm.Comment: 16 pages including 2 figure

Morphology of two dimensional fracture surface

We consider the morphology of two dimensional cracks observed in experimental results obtained from paper samples and compare these results with the numerical simulations of the random fuse model (RFM). We demonstrate that the data obey multiscaling at small scales but cross over to self-affine scaling at larger scales. Next, we show that the roughness exponent of the random fuse model is recovered by a simpler model that produces a connected crack, while a directed crack yields a different result, close to a random walk. We discuss the multiscaling behavior of all these models.Comment: slightly revise

Widespread sex differences in gene expression and splicing in the adult human brain

There is strong evidence to show that men and women differ in terms of neurodevelopment, neurochemistry and susceptibility to neurodegenerative and neuropsychiatric disease. The molecular basis of these differences remains unclear. Progress in this field has been hampered by the lack of genome-wide information on sex differences in gene expression and in particular splicing in the human brain. Here we address this issue by using post-mortem adult human brain and spinal cord samples originating from 137 neuropathologically confirmed control individuals to study whole-genome gene expression and splicing in 12 CNS regions. We show that sex differences in gene expression and splicing are widespread in adult human brain, being detectable in all major brain regions and involving 2.5% of all expressed genes. We give examples of genes where sex-biased expression is both disease-relevant and likely to have functional consequences, and provide evidence suggesting that sex biases in expression may reflect sex-biased gene regulatory structures

Membentuk generasi Islami melalui pembaharuan pendidikan Islam di Sekolah Dasar Islam Terpadu di Surabaya

Pembaharuan pada sebuah instansi pendidikan adalah sebuah hal yang wajar, tidak terkecuali pembaharuan yang ada pada Sekolah Islam Terpadu, terlebih jika tantangan yang ada pada masyarakat sangat mengharuskan dilakukan adanya pembaharuan, apalagi pembaharuan ini dilakukan untuk membentuk generasi Islami yang keberadaannya semakin hilang ditengah kemajuan zaman dan ditengah maraknya krisis moral pada masyarakat. Penelitian ini difokuskan pada permasalahan: (1) bagaimana generasi Islami dalam perspektif sekolah Islam terpadu; (2) bagaimana pembaharuan pendidikan Islam pada sekolah Islam terpadu; dan (3) bagaimana membentuk generasi Islami melalui pembaharuan pendidikan Islam pada Sekolah Islam terpadu.Jenis penelitian ini adalah kualitatif dengan pendekatan studi multi kasus, karena penelitian ini berusaha memahami secara detail terkait pembaharuan yang ada pada sekolah Islam terpadu. Data bersumber dari dokumen dan informan yang ditetapkan secara proporsional. Proses pengumpulan data menggunakan wawancara mendalam, observasi, dan dokumentasi. Data yang telah terkumpul dipetakan dan dianalisis sehingga terkumpul data yang relevan dengan tema penelitian. Selanjutnya data dilakukan analisis guna menyusun konsep dan gambaran dari temuan penelitian, dan terakhir pengujian kredibilitas data di cek dengan prosedur triangulasi sumber dan waktu serta pengujian transferability (keteralihan).Penelitian ini menghasilkan temuan berkaitan dengan pembaharauan pendidikan Islam dalam rangka pembentukan generasi Islami. Pertama, generasi Islami yang diharapkan akan terbentuk memiliki sepuluh karakter, yakni: al-sali>m al-a>qidah, al-s}ahi>h al-iba>dah, al-mati>n al-khu>luq, qadir> ‘ala al-kas}bi, al-muthaqqaf al-fiqri, al-qawiyy al-jismi, muja>hid li nafsihi, munazzam fi shu’unihi, ha>ris ‘ala al-waqtihi, na>fi’ li al-ghairihi. Kedua, pembaharuan yang dilakukan oleh Sekolah Dasar Islam Terpadu (SDIT) hanyalah sebuah modernisasi, yakni menutupi dan melengkapi kekurangan dari konsep pendidikan yang telah berjalan sebelumnya. Ketiga, upaya pembentukan generasi Islami pada SDIT tidak dilakukan memalui adanya pembaharuan, tetapi hanya melalui pembiasaan-pembiasaan yang dilakukan pada setiap aktivitas siswa dilingkungan sekolah, yang mana pembiasaan-pembiasaan ini semuanya dalam aspek dan berasas Islam sebagai dasarnya, sehingga karakter Islami yang dicita-citakan dapat terbentuk

Against quantiles: categorization of continuous variables in epidemiologic research, and its discontents

<p>Abstract</p> <p>Background</p> <p>Quantiles are a staple of epidemiologic research: in contemporary epidemiologic practice, continuous variables are typically categorized into tertiles, quartiles and quintiles as a means to illustrate the relationship between a continuous exposure and a binary outcome.</p> <p>Discussion</p> <p>In this paper we argue that this approach is highly problematic and present several potential alternatives. We also discuss the perceived drawbacks of these newer statistical methods and the possible reasons for their slow adoption by epidemiologists.</p> <p>Summary</p> <p>The use of quantiles is often inadequate for epidemiologic research with continuous variables.</p

Structural and Functional Characteristics of Color Vision Changes in Choroideremia

Color vision is considered a marker of cone function and its assessment in patients with retinal pathology is complementary to the assessments of spatial vision [best-corrected visual acuity (BCVA)] and contrast detection (perimetry). Rod-cone and chorioretinal dystrophies—such as choroideremia—typically cause alterations to color vision, making its assessment a potential outcome measure in clinical trials. However, clinical evaluation of color vision may be compromised by pathological changes to spatial vision and the visual field. The low vision Cambridge Color Test (lvCCT) was developed specifically to address these latter issues. We used the trivector version of the lvCCT to quantify color discrimination in a cohort of 53 patients with choroideremia. This test enables rapid and precise characterization of color discrimination along protan, deutan, and tritan axes more reliably than the historically preferred test for clinical trials, namely the Farnsworth Munsell 100 Hue test. The lvCCT demonstrates that color vision defects—particularly along the tritan axis—are seen early in choroideremia, and that this occurs independent of changes in visual acuity, pattern electroretinography and ellipsoid zone area on optical coherence tomography (OCT). We argue that the selective loss of tritan color discrimination can be explained by our current understanding of the machinery of color vision and the pathophysiology of choroideremia

Time from first presentation in primary care to treatment of symptomatic colorectal cancer:effect on disease stage and survival

BACKGROUND: British 5-year survival from colorectal cancer (CRC) is below the European average, but the reasons are unclear. This study explored if longer provider delays (time from presentation to treatment) were associated with more advanced stage disease at diagnosis and poorer survival. METHODS: Data on 958 people with CRC were linked with the Scottish Cancer Registry, the Scottish Death Registry and the acute hospital discharge (SMR01) dataset. Time from first presentation in primary care to first treatment, disease stage at diagnosis and survival time from date of first presentation in primary care were determined. Logistic regression and Cox survival analyses, both with a restricted cubic spline, were used to model stage and survival, respectively, following sequential adjustment of patient and tumour factors. RESULTS: On univariate analysis, those with <4 weeks from first presentation in primary care to treatment had more advanced disease at diagnosis and the poorest prognosis. Treatment delays between 4 and 34 weeks were associated with earlier stage (with the lowest odds ratio occurring at 20 weeks) and better survival (with the lowest hazard ratio occurring at 16 weeks). Provider delays beyond 34 weeks were associated with more advanced disease at diagnosis, but not increased mortality. Following adjustment for patient, tumour factors, emergency admissions and symptoms and signs, no significant relationship between provider delay and stage at diagnosis or survival from CRC was found. CONCLUSIONS: Although allowing for a nonlinear relationship and important confounders, moderately long provider delays did not impact adversely on cancer outcomes. Delays are undesirable because they cause anxiety; this may be fuelled by government targets and health campaigns stressing the importance of very prompt cancer diagnosis. Our findings should reassure patients. They suggest that a health service's primary emphasis should be on quality and outcomes rather than on time to treatment

A prospective study of peri-diagnostic and surgical wait times for patients with presumptive colorectal, lung, or prostate cancer

The objective of this study was to prospectively measure peri-diagnostic and surgical time intervals for patients with suspected colorectal, lung, or prostate cancer. Prospective eligible patients were referred to a regional hospital in Ottawa, Canada between February 2004 and February 2005 for diagnostic assessment of presumptive colorectal, lung, or prostate cancer. Chart abstractions were used to measure nine time intervals; the primary interval was the date of referral for diagnostic assessment to the date the patient was informed of the diagnosis. Health-related quality-of-life (HRQL) was assessed 5 days following the patient being informed of their diagnosis. The median (IQR) time for the primary interval was 71 (30–110), 37 (29–49), and 81 (56–100) days for colorectal, lung, and prostate patients, respectively (Kruskal–Wallis P=0.0001). This interval was significantly less for colorectal patients diagnosed with cancer than for those without cancer (median difference=59.0 days; Wilcoxon P=0.003). No differences in HRQL existed for patients with cancer and those without. Colorectal and prostate patients wait longer between referral for suspected cancer and being informed of their diagnosis than current recommendations. The shorter diagnostic intervals for colorectal patients with cancer suggest clinicians have an effective process for triaging patients referred for diagnostic assessment

The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XV. The Dynamical Clock: Reading Cluster Dynamical Evolution from the Segregation Level of Blue Straggler Stars

The parameter A +, defined as the area enclosed between the cumulative radial distribution of blue straggler stars (BSSs) and that of a reference population, is a powerful indicator of the level of BSS central segregation. As part of the Hubble Space Telescope UV Legacy Survey of Galactic globular clusters (GCs), here we present the BSS population and the determination of A + in 27 GCs observed out to about one half-mass radius. In combination with 21 additional clusters discussed in a previous paper, this provides us with a global sample of 48 systems (corresponding to ~32% of the Milky Way GC population), for which we find a strong correlation between A + and the ratio of cluster age to the current central relaxation time. Tight relations have also been found with the core radius and the central luminosity density, which are expected to change with the long-term cluster dynamical evolution. An interesting relation is emerging between A + and the ratio of the BSS velocity dispersion relative to that of main sequence turn-off stars, which measures the degree of energy equipartition experienced by BSSs in the cluster. These results provide further confirmation that BSSs are invaluable probes of GC internal dynamics and that A + is a powerful dynamical clock