Apsidal advance in SS 433?

Context. The Galactic microquasar SS 433 launches oppositely directed jets at speeds approximately a quarter of the speed of light. Both the speed and direction of the jets exhibit small fluctuations. A component of the speed variation has 13 day periodicity and the orbital phase at which its maximum speed occurs has advanced approximately 90 degrees in 25 years. Aims. To examine the possibility that these variations are associated with a mildly eccentric orbit and conditions necessary to achieve this apsidal advance. Methods. The advance of the orbital phase for maximum speed is taken to be advance of the apses of the putative elliptical orbit. It is compared with calculations of the effects of tides induced in the companion and also with gravitational perturbations from the circumbinary disc. These calculations are made in the light of recent results on the SS 433 system. Results. The 13 day periodicity in the speed of the jets of SS 433 might be attributed to a mildly elliptical orbit, through periodic approaches of the donor and the compact object. Advance of the apses of such an elliptical orbit due to tidal effects induced in a normal companion looks to be to small; if caused by the circumbinary disc the mass of the inner regions of that disc is ~ 0.15 solar masses.Comment: 2 pages, no figures To appear in A & A. No significant changes from original version poste

SS 433: The wiggle of the wind

The Balmer H alpha emission line in the stationary spectrum of SS 433 has a component originating in the wind above the accretion disk. The Doppler motion of this line is a blurred representation of the motion of the compact object accreting. I show how this may be understood in terms of emission lasting over a few days, like radiation from the jet bolides.Comment: 4 pages, 3 figures. A coda to my circumbinary disk studies. To appear in A&

Trapped particle makes 3D images.

A technique employing photophoretic trapping has been applied to the implementation of a three-dimensional (3D) volumetric display system. This may ultimately enable the production of high-quality, free space images.N/

Finite Temperature Behavior of Small Silicon and Tin Clusters: An Ab Initio Molecular Dynamics Study

The finite temperature behavior of small Silicon (Si$_{10}$, Si$_{15}$, and Si$_{20}$) and Tin (Sn$_{10}$ and Sn$_{20}$) clusters is studied using isokinetic Born-Oppenheimer molecular dynamics. The lowest equilibrium structures of all the clusters are built upon a highly stable tricapped trigonal prism unit which is seen to play a crucial role in the finite temperature behavior of these clusters. Thermodynamics of small tin clusters (Sn$_{10}$ and Sn$_{20}$) is revisited in light of the recent experiments on tin clusters of sizes 18-21 [G. A. Breaux et. al. Phys. Rev. B {\bf 71} 073410 (2005)]. We have calculated heat capacities using multiple histogram technique for Si$_{10}$, Sn$_{10}$ and Si$_{15}$ clusters. Our calculated specific heat curves have a main peak around 2300 K and 2200 K for Si$_{10}$ and Sn$_{10}$ clusters respectively. However, various other melting indicators such as root mean square bond length fluctuations, mean square displacements show that diffusive motion of atoms within the cluster begins around 650 K. The finite temperature behavior of Si$_{10}$ and Sn$_{10}$ is dominated by isomerization and it is rather difficult to discern the temperature range for transition region. On the other hand, Si$_{15}$ does show a liquid like behavior over a short temperature range followed by the fragmentation observed around 1800 K. Finite temperature behavior of Si$_{20}$ and Sn$_{20}$ show that these clusters do not melt but fragment around 1200 K and 650 K respectively.Comment: 9 figure

Digitally enhanced learning: Facing up to the camera.

At last the lecture room doors swing open and tenaciously guarding my cup of coffee I try to move against the great tsunami of emerging students. Immediately behind me follow two technical support staff weighed down with equipment and cables. We are well aware that the incumbent lecturer has (as usual) overrun his allotted time and so we are running late. The clock is ticking - my lecture is due to begin in seven minutes, and in terms of technology, there’s a lot of setting up to do.n/

Interpretation of observations of the circumbinary disk of SS 433

Context. The Galactic microquasar SS 433 is possessed of a circumbinary disk most clearly seen in the brilliant Balmer H alpha emission line. The orbital speed of the glowing material is an important determinant of the mass of the binary system. The circumbinary disk may be fed through the L2 point and in turn may feed a very extended radio feature known as the ruff. Aims. To present an analysis of spectroscopic optical data from H alpha and He I spectral lines which reveal the circumbinary disk. To use comparisons of the rather different signals to better understand the disk and improve estimates of the rotational speed of the inner rim. To present a simple model which naturally explains some apparently bizarre spectral variations with orbital phase. Methods. Published spectra, taken almost nightly over two orbital periods of the binary system, are analysed. H alpha and He I lines are analysed as superpositions of Gaussian components and a simple model constructed. Results. The data are understood in terms of a hot spot, generated by proximity of the compact object, rotating round the inner circumbinary disk with a period of 13 days. The glowing material fades with time, quite slowly for the H alpha source but more rapidly for the He I spectral lines. The orbital speed of the inner rim is approximately 250 km/s. Conclusions. The mass of the binary system must exceed 40 solar masses and the compact object must be a rather massive stellar black hole. The corollary is that the orbital speed of the companion must exceed 130 km/s.Comment: Article; 6 pages, 8 figures. The new version of 28 July 2010, to appear in A&A, is 8 pages and 8 figures. The principal addition is some discussion of the behaviour of a gas stream from the L2 point. I also have added a note about the possibility that absorption lines taken as indicating an orbital speed of 60 km/s for the companion might have their origin in the circumbinary dis

The human papillomaviruses (HPVs) and HPV DNA testing

The fact that some viruses act as carcinogens has long since been known. Amongst these viruses are some genotypes of the Human Papillomaviruses (HPVs). HPV is most frequently associated with cervical cancer, that is, cancer of the cervix or neck of the uterus. In fact, 95-100% of all cervical cancers are caused by infection with HPV. HPV also causes a high proportion of other anogenital cancers. In 1995, the International Agency for Research on Cancer (IARC) concluded that HPV types 16 and 18 are carcinogenic to humans; HPV types 31 and 33 are probably carcinogenic to humans whilst some HPV types other than 16, 18, 31 and 33 are possibly carcinogenic to humans. This review focuses first on the structure, classification and genome of these particular viruses. Particular attention is given to those features that play a role in the carcinogenicity of particular HPV genotypes. Given the close association between HPV and cervical cancer, detecting the presence of HPV in a particular patient and more specifically, the presence of particular genotypes of HPV, may give an indication of the likelihood of progression to precancerous and cancerous changes in the cervix. In fact, there is much evidence that screening of women with both cytology and HPV DNA tests increases sensitivity for detection of Cervical Intraepithelial Neoplasia (CIN) 3 or cancer sufficiently to permit longer screening intervals than with cytology alone. However, it is important to realize that the presence of HPV does not mean that a woman has or will develop cervical disease. Thus, there is still a dilemma as regards the real utility of HPV DNA testing. Screening and diagnostic procedures for cervical cancer will be discussed in the second part of this review, with special emphasis on HPV DNA testing. The benefits of HPV DNA testing in specific situations will be highlighted, particularly in the case of a diagnosis of Atypical Squamous Cell of Undetermined Significance (ASCUS).peer-reviewe

A new efficient free-rolling tyre-testing procedure for the parameterisation of vehicle dynamics tyre models

This paper describes an efficient tyre test procedure that can be used to collect the data required to parameterise empirical tyre models used in the computer simulations of vehicle dynamics. The new GS2MF FreeRolling test procedure develops established methodologies, such as the time measurement procedure from the TIME project and the MICH2MF measurement protocol developed as alternatives to traditional square matrix testing. The new process is designed to reduce the number of expensive tyre tests without compromising the accuracy of the generated tyre model parameters. The process is demonstrated by a programme of tyre testing carried out using the Calspan TIRF tyre testing facility in the USA, and it is shown here how the GS2MF Flat-Trac® tyre test procedure can be used more efficiently to parameterise the pure lateral and self-aligning moment components for the well-known ‘magic formula’ tyre model. This is achieved using a ‘cruise’-type procedure which is more representative of conditions existing when driving a real vehicle. During the tests, a novel automated logic approach is also proposed to manage the temperature of the tyres. Finally, graph sweeps are introduced at the start and the end of the tests, allowing a judgement to be made as to the influence of the tyre wear on the data obtained throughout the tests. The development of accurate and representative tyre models remains a significant challenge as vehicle manufacturers target increased use of virtual prototypes and simulations. This work contributes to this challenge by improving the efficiency of the expensive testing process needed to parameterise the models. </jats:p

Pre-invasive cervical disease and cervical carcinoma

Until a few years ago cervical cancer was one of the commonest type of cancer in women worldwide. Its incidence decreased dramatically following the implementation of the Papanicolaou (Pap) smear as a screening procedure. The Pap smear can detect a wide range of abnormalities of the cervix from benign cellular changes to precancerous conditions. Part of this review, will focus on this issue, specifically the abnormal and/or possibly precancerous findings that can be found in a Pap smear result. These will be classified according to the Bethesda system. One must emphasize here that most of these abnormalities regress on their own and do not need specific treatment. Yet, findings like the High-grade Squamous Intraepithelial Lesion (HSIL) have a high rate of progression to cancer and necessitate immediate management. The other half of this review will focus on cervical cancer in itself, a malignant and therefore invasive disease which, like all other cancers, can be fatal if left untreated. The extent of spread of the cancer is determined by the staging system, here described according to the International Federation of Gynecology and Obstetrics (FIGO). Staging is an important means of evaluating the treatment plans used.peer-reviewe