On the Challenges of Physical Implementations of RBMs

Restricted Boltzmann machines (RBMs) are powerful machine learning models, but learning and some kinds of inference in the model require sampling-based approximations, which, in classical digital computers, are implemented using expensive MCMC. Physical computation offers the opportunity to reduce the cost of sampling by building physical systems whose natural dynamics correspond to drawing samples from the desired RBM distribution. Such a system avoids the burn-in and mixing cost of a Markov chain. However, hardware implementations of this variety usually entail limitations such as low-precision and limited range of the parameters and restrictions on the size and topology of the RBM. We conduct software simulations to determine how harmful each of these restrictions is. Our simulations are designed to reproduce aspects of the D-Wave quantum computer, but the issues we investigate arise in most forms of physical computation

Magnetic field-induced quantum superconductor-insulator transition in Nb0.15Si0.85Nb_{0.15}Si_{0.85}

A study of magnetic-field tuned superconductor-insulator transitions in amorphous $Nb_{0.15}Si_{0.85}$ thin films shows that quantum superconductor-insulator transitions are characterized by an unambiguous signature -- a kink in the temperature profile of the critical magnetic field. Using this criterion, we show that the nature of the magnetic-field tuned superconductor-insulator transition depends on the orientation of the field with respect to the film. For perpendicular magnetic field, the transition is controlled by quantum fluctuations with indications for the existence of a Bose insulator; while for parallel magnetic field, the transition is classical, driven by the breaking of Cooper pairs at the temperature dependent critical field $H_{c2}$.Comment: 5 pages, 4 figure

A length scale for the superconducting Nernst signal above Tc_{c} in Nb0.15_{0.15}Si0.85_{0.85}

We present a study of the Nernst effect in amorphous superconducting thin films of Nb$_{0.15}$Si$_{0.85}$. The field dependence of the Nernst coefficient above T$_{c}$ displays two distinct regimes separated by a field scale set by the Ginzburg-Landau correlation length. A single function $F(\xi)$, with the correlation length as its unique argument set either by the zero-field correlation length (in the low magnetic field limit) or by the magnetic length (in the opposite limit), describes the Nernst coefficient. We conclude that the Nernst signal observed on a wide temperature ($30 \times T_c$) and field ($4 \times B_{c2}$) range is exclusively generated by short-lived Cooper pairs.Comment: 4 pages, 4 figure

Les relations entre l'armée et l'administration forestière en Algérie. Du début de la colonisation au début du XXe siècle

Du début de la colonisation à la fin du XIXe siècle, dans les territoires dont elle a la responsabilité, l'armée tente de résister à la politique forestière. Elle n'est pas contre le principe de la protection, mais elle refuse une application systématique, sans nuance, d'une réglementation mise au point en Métropole. En contact constant avec les indigènes, et parce qu'elle est consciente qu'on ne peut gérer les forêts d'une terre de colonisation méditerranéenne comme les forêts des Ardennes ou des Vosges, elle privilégie le maintien des coutumes, des habitudes pastorales, lorsqu'elle juge qu'elles ne présentent pas un danger réel

Communaux boisés et maintien de l'intégrité territoriale en Provence (1827-1900)

Parmi les mesures organisant la préservation des communaux boisés, il faut compter celles ayant trait au maintien de l'intégrité territoriale. Celles-ci passent tout d'abord par la délimitation partielle ou générale et le bornage, mesures destinées, en identifiant clairement les communaux boisés, à les mettre à l'abri de toutes contestations. De plus, pour protéger le patrimoine forestier devant revenir aux générations futures, les dirigeants municipaux doivent veiller à ce que leur surface reste constante, ceci impliquant une limitation de la disposition des communaux boisés

Les «constructions à distance prohibée» en Provence et en Dauphiné dans le code forestier de 1827 (1827-1900)

Montre comment l'administration a assuré la protection de la forêt en Provence et en Dauphiné au XIXème siècle

Incontinence : stress urinary incontinence treatment—surgery first?

A randomized trial involving 460 women with stress urinary incontinence compared physiotherapy with midurethral-sling surgery. We question whether the results, showing higher rates of improvement and cure for surgery than for physiotherapy, should change best practice and clinical practice guideline recommendations

Comparison of two methods for measuring the pubococcygeal line from sagittal-plane magnetic resonance imaging

Aims The pubococcygeal line (PCL) is an important reference line for determining measures of pelvic organ support on sagittal-plane magnetic resonance imaging (MRI); however, there is no consensus on where to place the posterior point of the PCL. As coccyx movement produced during pelvic floor muscle (PFM) contractions may affect other measures, optimal placement of the posterior point is important. This study compared two methods for measuring the PCL, with different posterior points, on T2-weighted sagittal MRI to determine the effect of coccygeal movement on measures of pelvic organ support in older women. Methods MRI of the pelvis was performed in the midsagittal plane, at rest and during PFM contractions, on 47 community-dwelling women 60 and over. The first PCL was measured to the tip of the coccyx (PCLtip) and the second to the sacrococcygeal joint (PCLjnt). Four measures of pelvic organ support were made using each PCL as the reference line: urethrovesical junction height, uterovaginal junction height, M-line and levator plate angle. Results During the PFM contraction the PCLtip shortened and lifted (P  0.05). The changes in the four measures of pelvic organ support were smaller when measured relative to the PCLtip as compared to those to the PCLjnt (P < 0.001). Conclusions Coccyx movement affected the length and position of the PCLtip, which resulted in underestimates of the pelvic-organ lift produced by the PFM contraction. Therefore, we recommend that the PCL be measured to the sacrococcygeal joint and not to the tip of the coccy