Authorship Attribution for Social Media Forensics Rocha, Anderson; Scheirer, Walter J.; Forstall, Christopher W. ...
IEEE transactions on information forensics and security,
01/2017, Letnik:
12, Številka:
1
Journal Article
Recenzirano
The veil of anonymity provided by smartphones with pre-paid SIM cards, public Wi-Fi hotspots, and distributed networks like Tor has drastically complicated the task of identifying users of social ...media during forensic investigations. In some cases, the text of a single posted message will be the only clue to an author's identity. How can we accurately predict who that author might be when the message may never exceed 140 characters on a service like Twitter? For the past 50 years, linguists, computer scientists, and scholars of the humanities have been jointly developing automated methods to identify authors based on the style of their writing. All authors possess peculiarities of habit that influence the form and content of their written works. These characteristics can often be quantified and measured using machine learning algorithms. In this paper, we provide a comprehensive review of the methods of authorship attribution that can be applied to the problem of social media forensics. Furthermore, we examine emerging supervised learning-based methods that are effective for small sample sizes, and provide step-by-step explanations for several scalable approaches as instructional case studies for newcomers to the field. We argue that there is a significant need in forensics for new authorship attribution algorithms that can exploit context, can process multi-modal data, and are tolerant to incomplete knowledge of the space of all possible authors at training time.
Beaked whales have mass stranded during some naval sonar exercises, but the cause is unknown. They are difficult to sight but can reliably be detected by listening for echolocation clicks produced ...during deep foraging dives. Listening for these clicks, we documented Blainville's beaked whales, Mesoplodon densirostris, in a naval underwater range where sonars are in regular use near Andros Island, Bahamas. An array of bottom-mounted hydrophones can detect beaked whales when they click anywhere within the range. We used two complementary methods to investigate behavioral responses of beaked whales to sonar: an opportunistic approach that monitored whale responses to multi-day naval exercises involving tactical mid-frequency sonars, and an experimental approach using playbacks of simulated sonar and control sounds to whales tagged with a device that records sound, movement, and orientation. Here we show that in both exposure conditions beaked whales stopped echolocating during deep foraging dives and moved away. During actual sonar exercises, beaked whales were primarily detected near the periphery of the range, on average 16 km away from the sonar transmissions. Once the exercise stopped, beaked whales gradually filled in the center of the range over 2-3 days. A satellite tagged whale moved outside the range during an exercise, returning over 2-3 days post-exercise. The experimental approach used tags to measure acoustic exposure and behavioral reactions of beaked whales to one controlled exposure each of simulated military sonar, killer whale calls, and band-limited noise. The beaked whales reacted to these three sound playbacks at sound pressure levels below 142 dB re 1 µPa by stopping echolocation followed by unusually long and slow ascents from their foraging dives. The combined results indicate similar disruption of foraging behavior and avoidance by beaked whales in the two different contexts, at exposures well below those used by regulators to define disturbance.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Summary Background Non-clear cell renal cell carcinomas are histologically and genetically diverse kidney cancers with variable prognoses, and their optimum initial treatment is unknown. We aimed to ...compare the mTOR inhibitor everolimus and the VEGF receptor inhibitor sunitinib in patients with non-clear cell renal cell carcinoma. Methods We enrolled patients with metastatic papillary, chromophobe, or unclassified non-clear cell renal cell carcinoma with no history of previous systemic treatment. Patients were randomly assigned (1:1) to receive everolimus (10 mg/day) or sunitinib (50 mg/day; 6-week cycles of 4 weeks with treatment followed by 2 weeks without treatment) administered orally until disease progression or unacceptable toxicity. Randomisation was stratified by Memorial Sloan Kettering Cancer Center risk group and papillary histology. The primary endpoint was progression-free survival in the intention-to-treat population using the RECIST 1.1 criteria. Safety was assessed in all patients who were randomly assigned to treatment. This study is registered with ClinicalTrials.gov , number NCT01108445. Findings Between Sept 23, 2010, and Oct 28, 2013, 108 patients were randomly assigned to receive either sunitinib (n=51) or everolimus (n=57). As of December, 2014, 87 progression-free survival events had occurred with two remaining active patients, and the trial was closed for the primary analysis. Sunitinib significantly increased progression-free survival compared with everolimus (8·3 months 80% CI 5·8–11·4 vs 5·6 months 5·5–6·0; hazard ratio 1·41 80% CI 1·03–1·92; p=0·16), although heterogeneity of the treatment effect was noted on the basis of histological subtypes and prognostic risk groups. No unexpected toxic effects were reported, and the most common grade 3–4 adverse events were hypertension (12 24% of 51 patients in the sunitinib group vs one 2% of 57 patients in the everolimus group), infection (six 12% vs four 7%), diarrhoea (five 10% vs one 2%), pneumonitis (none vs five 9%), stomatitis (none vs five 9%), and hand-foot syndrome (four 8% vs none). Interpretation In patients with metastatic non-clear cell renal cell carcinoma, sunitinib improved progression-free survival compared with everolimus. Future trials of novel agents should account for heterogeneity in disease outcomes based on genetic, histological, and prognostic factors. Funding Novartis and Pfizer.
Hybrid Class 1/Class 2 supported amine CO2 sorbents demonstrate superior performance under practical steam conditions, yet their amine immobilization and stabilization mechanisms are unclear. ...Uncovering the interactions responsible for the sorbents’ robust features is critical for further improvements and can facilitate practical applications. We employ solid state 29Si CP-MAS and 2-D FSLG 1H–13C CP HETCOR NMR spectroscopies to probe the overall molecular interactions of aminosilane/silica, polyamine poly(ethylenimine), PEI/silica, and hybrid aminosilane/PEI/silica sorbents. A unique, sequential impregnation sorbent preparation method is executed in a diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) setup to decouple amine binding mechanisms at the amine–silica interface from those within bulk amine layers. These mechanisms are correlated with each sorbents’ resistance to accelerated liquid H2O and TGA steam treatments (H2O stability) and to oxidative degradation (thermal stability). High percentages of CO2 capture retained (PCR) and organic content retained (OCR) values after H2O testing of N-(3-(trimethoxysilyl)propyl)ethylenediamine (TMPED)/PEI and (3-aminopropyl)trimethoxysilane (APTMS)/PEI hybrid sorbents are associated with a synergistic stabilizing effect of the amine species observed during oxidative degradation (thermal gravimetric analysis-differential scanning calorimetry, TGA-DSC). Solid state NMR spectroscopy reveals that the synergistic effect of the TMPED/PEI mixture is manifested by the formation of hydrogen-bonded PEI–NH2···NH2–TMPED and PEI–NH2···HO–Si/O–Si–O (TMPED, T2) linkages within the sorbent. DRIFTS further determines that PEI enhances the grafting of TMPED to silica and that PEI is dispersed among a stable network of polymerized TMPED in the bulk, utilizing H-bonded linkages. These findings provide the scientific basis for establishing a Class 4 category for aminosilane/polyamine/silica hybrid sorbents.
Parasite–host and insect–plant research have divergent traditions despite the fact that most phytophagous insects live parasitically on their host plants. In parasitology it is a traditional ...assumption that parasites are typically highly specialized; cospeciation between parasites and hosts is a frequently expressed default expectation. Insect–plant theory has been more concerned with host shifts than with cospeciation, and more with hierarchies among hosts than with extreme specialization. We suggest that the divergent assumptions in the respective fields have hidden a fundamental similarity with an important role for potential as well as actual hosts, and hence for host colonizations via ecological fitting. A common research program is proposed which better prepares us for the challenges from introduced species and global change.
Parasites are typically assumed to be highly specialized on their hosts and well adapted to them, yet they frequently colonize new hosts – including humans, causing EIDs.
This parasite paradox has caused a growing unease with the traditional assumptions in parasitology, which differ markedly from those in the field of insect–plant studies.
We report the results of a workshop where parasitologists and insect–plant researchers met to explore the possibility that the two systems may be more similar than the divergent research traditions suggest, so that a common research program can be developed to better prepare us for future challenges.
Joint stability is one of the goals of any joint replacement. The contribution of prosthesis design to sagittal stability in total knee arthroplasty (TKA) has emerged as an area of interest. The ...purpose of this study was to evaluate the sagittal stability of four prosthesis types and determine the effect on patient reported outcome measures (PROMs).
A matched-cohort cross-sectional study was performed on 60 patients after TKA at 1-year follow-up. Three surgeons performed 10 medially stabilized (MS) TKA and 10 non-MS TKA. Sagittal stability was assessed by a blinded observer using a KT-1000 arthrometer, Lachman’s test, and the anterior drawer test. PROMs (Oxford, Knee Injury and Osteoarthritis Outcome Score, Western Ontario and McMaster Universities Osteoarthritis Index, Forgotten joint score) and visual analog scale assessed function and satisfaction.
MS TKA had significantly decreased translation on KT-1000 and improved stability compared with non-MS TKA (P < .05). Increased PROMs were demonstrated in the MS TKA group compared with the non-MS TKA group (P < .05). When divided based on objective stability, regardless of the prosthesis type, patients with a stable knee had superior PROMs (P < .05), particularly in sport-related questions.
The MS TKA had significantly greater sagittal stability, improved PROMs, and satisfaction compared with non-MS TKA. Independent of prosthesis design, patients with greater sagittal stability demonstrated improved PROMs.
A clinical trial of hydrocortisone, vitamin C, and thiamine for treating sepsis raises questions regarding evidence generation. Researchers must adopt a cumulative approach that takes previous ...clinical trials of other treatments into account.
The purpose of this study was to examine the effects of acute normobaric (NH, decreased FiO
) and hypobaric (HH, 4200 m ascent) hypoxia exposures compared to sea level (normobaric normoxia, NN). ...Tissue oxygenation, cardiovascular, and body fluid variables measured during rest and a 3-min step-test following 90-min exposures (NH, HH, NN). Muscle oxygenated hemoglobin (O
Hb) decreased, and muscle deoxygenated hemoglobin (HHb) increased environmentally independent from rest to exercise (p < 0.001). During exercise, brain O
Hb was lower at HH compared to NN (p = 0.007), trending similarly with NH (p = 0.066), but no difference between NN and NH (p = 0.158). During exercise, HR at NH (141 ± 4 beats·min
) and HH (141 ± 3 beats·min
) were higher than NN (127 ± 44 beats·min
, p = 0.002), but not each other (p = 0.208). During exercise, stroke volume at HH (109.6 ± 4.1 mL·beat
) was higher than NH (97.8 ± 3.3 mL·beat
) and NN (99.8 ± 3.9 mL·beat
, p ≤ 0.010) with no difference between NH and NN (p = 0.481). During exercise, cardiac output at NH (13.8 ± 0.6 L) and HH (15.5 ± 0.7 L) were higher than NN (12.6 ± 0.5 L, p ≤ 0.006) with HH also higher than NH (p = 0.001). During acute hypoxic stimuli, skeletal muscle maintains oxygenation whereas the brain does not. These differences may be mediated by environmentally specific cardiovascular compensation. Thus, caution is advised when equating NH and HH.
ABSTRACT
One challenge for applying current weak lensing analysis tools to the Nancy Grace Roman Space Telescope is that individual images will be undersampled. Our companion paper presented an ...initial application of Imcom – an algorithm that builds an optimal mapping from input to output pixels to reconstruct a fully sampled combined image – on the Roman image simulations. In this paper, we measure the output noise power spectra, identify the sources of the major features in the power spectra, and show that simple analytic models that ignore sampling effects underestimate the power spectra of the coadded noise images. We compute the moments of both idealized injected stars and fully simulated stars in the coadded images, and their one- and two-point statistics. We show that the idealized injected stars have root-mean-square ellipticity errors (1–6) × 10−4 per component depending on the band; the correlation functions are ≥2 orders of magnitude below requirements, indicating that the image combination step itself is using a small fraction of the overall Roman second moment error budget, although the fourth moments are larger and warrant further investigation. The stars in the simulated sky images, which include blending and chromaticity effects, have correlation functions near the requirement level (and below the requirement level in a wide-band image constructed by stacking all four filters). We evaluate the noise-induced biases in the ellipticities of injected stars, and explain the resulting trends with an analytical model. We conclude by enumerating the next steps in developing an image coaddition pipeline for Roman.
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