109 research outputs found
The Pioneer Anomaly
Radio-metric Doppler tracking data received from the Pioneer 10 and 11
spacecraft from heliocentric distances of 20-70 AU has consistently indicated
the presence of a small, anomalous, blue-shifted frequency drift uniformly
changing with a rate of ~6 x 10^{-9} Hz/s. Ultimately, the drift was
interpreted as a constant sunward deceleration of each particular spacecraft at
the level of a_P = (8.74 +/- 1.33) x 10^{-10} m/s^2. This apparent violation of
the Newton's gravitational inverse-square law has become known as the Pioneer
anomaly; the nature of this anomaly remains unexplained. In this review, we
summarize the current knowledge of the physical properties of the anomaly and
the conditions that led to its detection and characterization. We review
various mechanisms proposed to explain the anomaly and discuss the current
state of efforts to determine its nature. A comprehensive new investigation of
the anomalous behavior of the two Pioneers has begun recently. The new efforts
rely on the much-extended set of radio-metric Doppler data for both spacecraft
in conjunction with the newly available complete record of their telemetry
files and a large archive of original project documentation. As the new study
is yet to report its findings, this review provides the necessary background
for the new results to appear in the near future. In particular, we provide a
significant amount of information on the design, operations and behavior of the
two Pioneers during their entire missions, including descriptions of various
data formats and techniques used for their navigation and radio-science data
analysis. As most of this information was recovered relatively recently, it was
not used in the previous studies of the Pioneer anomaly, but it is critical for
the new investigation.Comment: 165 pages, 40 figures, 16 tables; accepted for publication in Living
Reviews in Relativit
A mutation in the viral sensor 2’-5’-oligoadenylate synthetase 2 causes failure of lactation
We identified a non-synonymous mutation in Oas2 (I405N), a sensor of viral double-stranded RNA, from an ENU-mutagenesis screen designed to discover new genes involved in mammary development. The mutation caused post-partum failure of lactation in healthy mice with otherwise normally developed mammary glands, characterized by greatly reduced milk protein synthesis coupled with epithelial cell death, inhibition of proliferation and a robust interferon response. Expression of mutant but not wild type Oas2 in cultured HC-11 or T47D mammary cells recapitulated the phenotypic and transcriptional effects observed in the mouse. The mutation activates the OAS2 pathway, demonstrated by a 34-fold increase in RNase L activity, and its effects were dependent on expression of RNase L and IRF7, proximal and distal pathway members. This is the first report of a viral recognition pathway regulating lactation.Samantha R. Oakes, David Gallego-Ortega, Prudence M. Stanford, Simon Junankar, Wendy Wing Yee Au ... Moira K. O’Bryan ... et al
Evidence for widespread hydrated minerals on asteroid (101955) Bennu
Early spectral data from the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission reveal evidence for abundant hydrated minerals on the surface of near-Earth asteroid (101955) Bennu in the form of a near-infrared absorption near 2.7 µm and thermal infrared spectral features that are most similar to those of aqueously altered CM-type carbonaceous chondrites. We observe these spectral features across the surface of Bennu, and there is no evidence of substantial rotational variability at the spatial scales of tens to hundreds of metres observed to date. In the visible and near-infrared (0.4 to 2.4 µm) Bennu’s spectrum appears featureless and with a blue (negative) slope, confirming previous ground-based observations. Bennu may represent a class of objects that could have brought volatiles and organic chemistry to Earth
Multi-messenger observations of a binary neutron star merger
On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta
The dynamic geophysical environment of (101955) Bennu based on OSIRIS-REx measurements
The top-shaped morphology characteristic of asteroid (101955) Bennu, often found among fast-spinning asteroids and binary asteroid primaries, may have contributed substantially to binary asteroid formation. Yet a detailed geophysical analysis of this morphology for a fast-spinning asteroid has not been possible prior to the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission. Combining the measured Bennu mass and shape obtained during the Preliminary Survey phase of the OSIRIS-REx mission, we find a notable transition in Bennu’s surface slopes within its rotational Roche lobe, defined as the region where material is energetically trapped to the surface. As the intersection of the rotational Roche lobe with Bennu’s surface has been most recently migrating towards its equator (given Bennu’s increasing spin rate), we infer that Bennu’s surface slopes have been changing across its surface within the last million years. We also find evidence for substantial density heterogeneity within this body, suggesting that its interior is a mixture of voids and boulders. The presence of such heterogeneity and Bennu’s top shape are consistent with spin-induced failure at some point in its past, although the manner of its failure cannot yet be determined. Future measurements by the OSIRIS-REx spacecraft will provide insight into and may resolve questions regarding the formation and evolution of Bennu’s top-shape morphology and its link to the formation of binary asteroids
EFEKTIVITAS PENGAWASAN UNIT KERJA ANTI FRAUD PADA BANK MUAMALAT INDONESIA
Perkembangan perbankan syari‟ah di Indonesia demikian pesat yang
ditandai dengan berdirinya Bank Muamalat Indonesia. Perkembangan ini
berimplikasi pada besarnya tantangan perbankan syari‟ah di Indonesia terutama
dalam mempertahankan identitasnya sebagai perusahaan yang bergerak
berlandaskan prinsip-prinsip syari‟ah. Sejak berdirinya perbankan
syariah,berbagai kontroversi muncul dari masyarakat, masalah yang paling
banyak disorot adalah pelekatan label syariah pada institusi keuangan Islam yang
masih dianggap belum layak. Keraguan masyarakat tersebut seolah terjawab
dengan munculnya kasus yang cukup menggemparkan yakni kasus fraud (tindak
kecurangan) yang terjadi di lembaga syariah.
Bank Muamalat Indonesia merupakan bank syari‟ah pertama yang muncul
dengan gagasan bank murni syari‟ah. Akan tetapi, bank Muamalat Indonesia juga
tak luput dari kasus fraud yang dilakukan oleh karyawan bank tersebut.
Berdasarkan Laporan Tahunan BMI menyebutkan bahwa telah terjadi
peningkatan kasus fraud dari tahun sebelumnya yang berjumlah 18 kasus menjadi
82 kasus pada tahun 2016. Padahal perusahaan yang menggunakan identitas
syariah seharusnya dapat lebih meminimalisir bahkan meniadakan resiko
terjadinya kasus fraud dengan adanya internal control perusahaan. Dari latar
belakang tersebut, peneliti berusaha mendalami peran pengawasan Unit Kerja
Anti Fraud dalam fraud preventive pada Bank Muamalat Indonesia. Penelitian ini
merupakan penelitin pustaka yang bersifat deskriptif analisis dengan pendekatan
kualitatif. Adapun sumber bahan hukum primer yang dipakai yaitu berdasarkan
Laporan Tahunan Bank Muamalat Indonesia Tahun 2016. Sedangkan sumber
bahan hukum sekunder berupa buku-buku, jurnal,karya ilmiah, artikel, terkait
dengan strategi anti fraud perbankan syariah.
Dari hasil penelitian dikemukakan bahwa peningkatan kasus fraud yang
terjadi pada Bank Muamalat Indonesia disebabkan kurang efektifnya pengawasan
Unit Kerja Anti Fraud. Hal ini dikarenakan kegiatan yang dilakukan selama tahun
2016 belum menujukkan adanya usaha preventif terhadap kasus fraud. Sedangkan
pencegahan merupakan pilar penting dalam keefektivan sebuah pengawasan.
Tujuan perusahaan dalam mencegah fraud dapat tercapai, jika fungsi pengawasan
dilakukan sebelum terjadinya penyimpangan-penyimpangan sehingga lebih
bersifat mencegah (prefentive control). Oleh karena itu, keefektivan pengawasan
Unit Kerja Anti Fraud diharapkan dapat meminimalisir tindak kecurangan demi
mewujudkan perusahaan yang patuh terhadap ketentuan syariah sesuai dengan
identitas perusahaan.
vii
Usaha pencegahan terjadinya kasus pada Bank Muamalat Indonesia
diharapkan dapat menjadi bukti terlaksananya tatakelola perusahaan (Good
Corporate Governance) pada Bank Syari‟ah dengan baik. Hal ini berdasarkan
dalam dalam perbankan syariah dikenal adanya prinsip-prinsip syariah yang
mendukung bagi terlaksananya prinsip GCG yakni keharusan bagi subjek hukum
termasuk bank untuk menerapkan prinsip kejujuran (shiddiq), edukasi kepada
masyarakat (tabligh), kepercayaan (amanah), dan pengelolaan secara profesional
(fathanah)
A cognitive-motor intervention using a dance video game to enhance foot placement accuracy and gait under dual task conditions in older adults: a randomized controlled trial
Evaluation of appendicitis risk prediction models in adults with suspected appendicitis
Background
Appendicitis is the most common general surgical emergency worldwide, but its diagnosis remains challenging. The aim of this study was to determine whether existing risk prediction models can reliably identify patients presenting to hospital in the UK with acute right iliac fossa (RIF) pain who are at low risk of appendicitis.
Methods
A systematic search was completed to identify all existing appendicitis risk prediction models. Models were validated using UK data from an international prospective cohort study that captured consecutive patients aged 16–45 years presenting to hospital with acute RIF in March to June 2017. The main outcome was best achievable model specificity (proportion of patients who did not have appendicitis correctly classified as low risk) whilst maintaining a failure rate below 5 per cent (proportion of patients identified as low risk who actually had appendicitis).
Results
Some 5345 patients across 154 UK hospitals were identified, of which two‐thirds (3613 of 5345, 67·6 per cent) were women. Women were more than twice as likely to undergo surgery with removal of a histologically normal appendix (272 of 964, 28·2 per cent) than men (120 of 993, 12·1 per cent) (relative risk 2·33, 95 per cent c.i. 1·92 to 2·84; P < 0·001). Of 15 validated risk prediction models, the Adult Appendicitis Score performed best (cut‐off score 8 or less, specificity 63·1 per cent, failure rate 3·7 per cent). The Appendicitis Inflammatory Response Score performed best for men (cut‐off score 2 or less, specificity 24·7 per cent, failure rate 2·4 per cent).
Conclusion
Women in the UK had a disproportionate risk of admission without surgical intervention and had high rates of normal appendicectomy. Risk prediction models to support shared decision‐making by identifying adults in the UK at low risk of appendicitis were identified
Linkage analysis and QTL mapping using SNP dosage data in a tetraploid potato mapping population
New sequencing and genotyping technologies have enabled researchers to generate high density SNP genotype data for mapping populations. In polyploid species, SNP data usually contain a new type of information, the allele dosage, which is not used by current methodologies for linkage analysis and QTL mapping. Here we extend existing methodology to use dosage data on SNPs in an autotetraploid mapping population. The SNP dosages are inferred from allele intensity ratios using normal mixture models. The steps of the linkage analysis (testing for distorted segregation, clustering SNPs, calculation of recombination fractions and LOD scores, ordering of SNPs and inference of parental phase) are extended to use the dosage information. For QTL analysis, the probability of each possible offspring genotype is inferred at a grid of locations along the chromosome from the ordered parental genotypes and phases and the offspring dosages. A normal mixture model is then used to relate trait values to the offspring genotypes and to identify the most likely locations for QTLs. These methods are applied to analyse a tetraploid potato mapping population of parents and 190 offspring, genotyped using an Infinium 8300 Potato SNP Array. Linkage maps for each of the 12 chromosomes are constructed. The allele intensity ratios are mapped as quantitative traits to check that their position and phase agrees with that of the corresponding SNP. This analysis confirms most SNP positions, and eliminates some problem SNPs to give high-density maps for each chromosome, with between 74 and 152 SNPs mapped and between 100 and 300 further SNPs allocated to approximate bins. Low numbers of double reduction products were detected. Overall 3839 of the 5378 polymorphic SNPs can be assigned putative genetic locations. This methodology can be applied to construct high-density linkage maps in any autotetraploid species, and could also be extended to higher autopolyploids
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