Analyzing X-ray variability by State Space Models

In recent years, autoregressive models have had a profound impact on the description of astronomical time series as the observation of a stochastic process. These methods have advantages compared with common Fourier techniques concerning their inherent stationarity and physical background. If autoregressive models are used, however, it has to be taken into account that real data always contain observational noise often obscuring the intrinsic time series of the object. We apply the technique of a Linear State Space Model which explicitly models the noise of astronomical data and allows to estimate the hidden autoregressive process. As an example, we have analysed a sample of Active Galactic Nuclei (AGN) observed with EXOSAT and found evidence for a relationship between the relaxation timescale and the spectral hardness.Comment: 4 pages, Latex, uses Kluwer Style file crckapb.cls To appear in Proc. of Astronomical Time Series, Tel Aviv, 199

The use of the internet in small to medium-sized enterprises

Information technology, particularly the Internet has the potential to radically changethe way business is conducted, offering a competitive edge and a gateway to theglobal marketplace. The explosive growth and commercialisation of the Internet hasopened up a vast arena providing more opportunities for businesses, particularlySMEs to sell their products and service to a global audience than they would have beable to afford to reach using the traditional methods. There is tremendous potential forSMEs to harness the power of the Internet to improve their productivity and sharpentheir competitive edge in both local and international markets. The Internet is viewedas a means through which SMEs could extend their geographic reach at minimal costand to integrate and expand their business practices globally. Through such means itis argued that small companies could compete effectively against larger firms as theInternet is believed to be a great equaliser. The contribution of SMEs is extremelyimportant to the economy of many countries and their contribution cannot be overemphasised. SMEs account for more than 50% of private sector employment in theUK and are currently contributing most of the private sector employment growth.This research reports on the empirical study of SMEs usage of the Internet. Theintention is to present evidence on the current status of Internet use among SMEs andshow the factors that influence their decision to adopt the Internet in business.Although the Internet has experienced tremendous growth world wide, very littleempirical research has been conducted to examine this phenomenon in SMEs context.Questions about what SMEs are using the Internet for and what is driving them to usethe technology in their business are still lacking. It is therefore of importance thatinsight be gained into how SMEs are currently using the Internet and the factors thatinfluence their decision to adopt the Internet in business. In order to achieve theseobjectives, the research uses a quantitative and qualitative approach in order toprovide an in-depth description of how SMEs currently use the Internet and thefactors that influence their decision to adopt it. A questionnaire was used to survey 400 SMEs in the UK and 92 usable response(23%) were received. The survey result shows that communication, customer services,information gathering, and advertising are the areas the Internet is used most in SMEs.While the case study result shows that technological, organisational andenvironmental factors influence SMEs' decision to adopt the Internet. These factorsare used to develop a theoretical model for conceptualising the organisational issuesaround the adoption and use of the Internet--issues that have been largely missingfrom contemporary discussions of Internet usage in SMEs. The study thus hasimportant implications for research and practice. Specifically, the theoretical modeland findings suggest that technological and organisational factors, rather thanenvironmental factors, play a significant role in Internet adoption. Similarly, the studysuggests that practitioners will be better able to adopt the Internet in business, if theyunderstand how these factors influence its adoption and usage. The limitations of thestudy, the contributions of the research, the implications of the research findings andfuture research are discussed

Does virtual reality simulation have a role in training trauma and orthopaedic surgeons?

AIMS: The aim of this study was to assess the current evidence relating to the benefits of virtual reality (VR) simulation in orthopaedic surgical training, and to identify areas of future research. MATERIALS AND METHODS: A literature search using the MEDLINE, Embase, and Google Scholar databases was performed. The results' titles, abstracts, and references were examined for relevance. RESULTS: A total of 31 articles published between 2004 and 2016 and relating to the objective validity and efficacy of specific virtual reality orthopaedic surgical simulators were identified. We found 18 studies demonstrating the construct validity of 16 different orthopaedic virtual reality simulators by comparing expert and novice performance. Eight studies have demonstrated skill acquisition on a simulator by showing improvements in performance with repeated use. A further five studies have demonstrated measurable improvements in operating theatre performance following a period of virtual reality simulator training. CONCLUSION: The demonstration of 'real-world' benefits from the use of VR simulation in knee and shoulder arthroscopy is promising. However, evidence supporting its utility in other forms of orthopaedic surgery is lacking. Further studies of validity and utility should be combined with robust analyses of the cost efficiency of validated simulators to justify the financial investment required for their use in orthopaedic training. Cite this article: Bone Joint J 2018;100-B:559-65

A direct image of the obscuring disk surrounding an active galactic nucleus

Active galactic nuclei (AGN) are generally accepted to be powered by the release of gravitational energy in a compact accretion disk surrounding a massive black hole. Such disks are also necessary to collimate powerful radio jets seen in some AGN. The unifying classification schemes for AGN further propose that differences in their appearance can be attributed to the opacity of the accreting material, which may obstruct our view of the central region of some systems. The popular model for the obscuring medium is a parsec-scale disk of dense molecular gas, although evidence for such disks has been mostly indirect, as their angular size is much smaller than the resolution of conventional telescopes. Here we report the first direct images of a pc-scale disk of ionised gas within the nucleus of NGC 1068, the archetype of obscured AGN. The disk is viewed nearly edge-on, and individual clouds within the ionised disk are opaque to high-energy radiation, consistent with the unifying classification scheme. In projection, the disk and AGN axes align, from which we infer that the ionised gas disk traces the outer regions of the long-sought inner accretion disk.Comment: 14 pages, LaTeX, PSfig, to appear in Nature. also available at http://hethp.mpe-garching.mpg.de/Preprint

Eosinophils Are Important for Protection, Immunoregulation and Pathology during Infection with Nematode Microfilariae

Eosinophil responses typify both allergic and parasitic helminth disease. In helminthic disease, the role of eosinophils can be both protective in immune responses and destructive in pathological responses. To investigate whether eosinophils are involved in both protection and pathology during filarial nematode infection, we explored the role of eosinophils and their granule proteins, eosinophil peroxidase (EPO) and major basic protein-1 (MBP-1), during infection with Brugia malayi microfilariae. Using eosinophil-deficient mice (PHIL), we further clarify the role of eosinophils in clearance of microfilariae during primary, but not challenge infection in vivo. Deletion of EPO or MBP-1 alone was insufficient to abrogate parasite clearance suggesting that either these molecules are redundant or eosinophils act indirectly in parasite clearance via augmentation of other protective responses. Absence of eosinophils increased mast cell recruitment, but not other cell types, into the broncho-alveolar lavage fluid during challenge infection. In addition absence of eosinophils or EPO alone, augmented parasite-induced IgE responses, as measured by ELISA, demonstrating that eosinophils are involved in regulation of IgE. Whole body plethysmography indicated that nematode-induced changes in airway physiology were reduced in challenge infection in the absence of eosinophils and also during primary infection in the absence of EPO alone. However lack of eosinophils or MBP-1 actually increased goblet cell mucus production. We did not find any major differences in cytokine responses in the absence of eosinophils, EPO or MBP-1. These results reveal that eosinophils actively participate in regulation of IgE and goblet cell mucus production via granule secretion during nematode-induced pathology and highlight their importance both as effector cells, as damage-inducing cells and as supervisory cells that shape both innate and adaptive immunity

Bisphosphonates and atypical subtrochanteric fractures of the femur

$\textbf{Objectives}$ Bisphosphonates are widely used as first-line treatment for primary and secondary prevention of fragility fractures. Whilst they have proved effective in this role, there is growing concern over their long-term use, with much evidence linking bisphosphonate-related suppression of bone remodelling to an increased risk of atypical subtrochanteric fractures of the femur (AFFs). The objective of this article is to review this evidence, while presenting the current available strategies for the management of AFFs. $\textbf{Methods}$ We present an evaluation of current literature relating to the pathogenesis and treatment of AFFs in the context of bisphosphonate use. $\textbf{Results}$ Six broad themes relating to the pathogenesis and management of bisphosphonate-related AFFs are presented. The key themes in fracture pathogenesis are: bone microdamage accumulation; altered bone mineralisation and altered collagen formation. The key themes in fracture management are: medical therapy and surgical therapy. In addition, primary prevention strategies for AFFs are discussed. $\textbf{Conclusions}$ This article presents current knowledge about the relationship between bisphosphonates and the development of AFFs, and highlights key areas for future research. In particular, studies aimed at identifying at-risk subpopulations and organising surveillance for those on long-term therapy will be crucial in both increasing our understanding of the condition, and improving population outcomes

“Surgical” Abdomen in a Patient with Chronic Lymphocytic Leukemia: A Case of Acquired Angioedema

# The Author(s) 2011. This article is published with open access at Springerlink.com Introduction Acquired angioedema (AAE), an acquired deficiency of C1esterase inhibitor, is a medically treatable condition which can cause severe abdominal pain mimicking an acute surgical abdomen. This disorder is strongly associated with chronic lymphocytic leukemia (CLL) and other indolent lymphoplasmacytic disorders. Discussion We describe a patient with known CLL who developed incapacitating, recurrent severe abdominal pains, culminating in partial bowel resection. Signs, symptoms, laboratory and pathologic findings demonstrated AAE

The characteristic blue spectra of accretion disks in quasars as uncovered in the infrared

Quasars are thought to be powered by supermassive black holes accreting surrounding gas. Central to this picture is a putative accretion disk which is believed to be the source of the majority of the radiative output. It is well known, however, that the most extensively studied disk model -- an optically thick disk which is heated locally by the dissipation of gravitational binding energy -- is apparently contradicted by observations in a few major respects. In particular, the model predicts a specific blue spectral shape asymptotically from the visible to the near-infrared, but this is not generally seen in the visible wavelength region where the disk spectrum is observable. A crucial difficulty was that, toward the infrared, the disk spectrum starts to be hidden under strong hot dust emission from much larger but hitherto unresolved scales, and thus has essentially been impossible to observe. Here we report observations of polarized light interior to the dust-emiting region that enable us to uncover this near-infrared disk spectrum in several quasars. The revealed spectra show that the near-infrared disk spectrum is indeed as blue as predicted. This indicates that, at least for the outer near-infrared-emitting radii, the standard picture of the locally heated disk is approximately correct. The model problems at shorter wavelengths should then be directed toward a better understanding of the inner parts of the revealed disk. The newly uncovered disk emission at large radii, with more future measurements, will also shed totally new light on the unanswered critical question of how and where the disk ends.Comment: published in Nature, 24 July 2008 issue. Supplementary Information can be found at http://www.mpifr-bonn.mpg.de/div/ir-interferometry/suppl_info.pdf Published version can be accessed from http://www.nature.com/nature/journal/v454/n7203/pdf/nature07114.pd