Modular Synchronization in Multiversion Databases: Version Control and Concurrency Control

In this paper we propose a version control mechanism that enhances the modularity and extensibility of multiversion concurrency control algorithms. We decouple the multiversion algorithms into two components: version control and concurrency control. This permits modular development of multiversion protocols, and simplifies the task of proving the correctness of these protocols. An interesting feature of our framework is that the execution of read-only transactions becomes completely independent of the underlying concurrency control implementation. Also, algorithms with the version control mechanism have several advantages over most other multiversion algorithms

Prehistoric Copper Technology in India : A Review

Copper has been used by mankind from 5" to 2nd Millennia BC. The paper traced how metal technology has been part of the reparative of the technologies pertaining to ceramics, stone industry, and even architecture. No doubt, the first use of copper must have been of native copper. With the growth of urbanization, especially of the Indus civil-ization, the abundance of metal and technology advance progressed by leaps and bounds. The Archaeo-Metallurgical studies help a lot to know about typology of artifacts, technologies used, source of metal, what techniques diff-erent cultures used to make them artifact, mining tech-nology? A lot remains to be done: relating ore bodies to the artifact, metallographic studies to known techniques of artifact making, alloying pattern minerals used, geo-chemistry of ore bodies to devise ways to fingerprint them through trace impurity patterns and lead isotope geochemistry etc. No less important are the ethno-archaeological studies to understand the man behind the technology and his artifact. A lot more can be achieved with the joint effort of metallurgical labs. and the archeologists

Distilling Quantum Entanglement via Mode-Matched Filtering

We propose a new avenue towards distillation of quantum entanglement that is implemented by directly passing the entangled qubits through a mode-matched filter. This approach can be applied to a common class of entanglement impurities appearing in photonic systems where the impurities inherently occupy different spatiotemporal modes than the entangled qubits. As a specific application, we show that our method can be used to significantly purify the telecom-band entanglement generated via the Kerr nonlinearity in single-mode fibers where a substantial amount of Raman-scattering noise is concomitantly produced.Comment: 6 pages, 2 figures, to appear in Phys. Rev.

The refractive index and wave vector in passive or active media

Materials that exhibit loss or gain have a complex valued refractive index $n$. Nevertheless, when considering the propagation of optical pulses, using a complex $n$ is generally inconvenient -- hence the standard choice of real-valued refractive index, i.e. n_s = \RealPart (\sqrt{n^2}). However, an analysis of pulse propagation based on the second order wave equation shows that use of $n_s$ results in a wave vector \emph{different} to that actually exhibited by the propagating pulse. In contrast, an alternative definition n_c = \sqrt{\RealPart (n^2)}, always correctly provides the wave vector of the pulse. Although for small loss the difference between the two is negligible, in other cases it is significant; it follows that phase and group velocities are also altered. This result has implications for the description of pulse propagation in near resonant situations, such as those typical of metamaterials with negative (or otherwise exotic) refractive indices.Comment: Phys. Rev. A, to appear (2009

What is Holding Back Convnets for Detection?

Convolutional neural networks have recently shown excellent results in general object detection and many other tasks. Albeit very effective, they involve many user-defined design choices. In this paper we want to better understand these choices by inspecting two key aspects "what did the network learn?", and "what can the network learn?". We exploit new annotations (Pascal3D+), to enable a new empirical analysis of the R-CNN detector. Despite common belief, our results indicate that existing state-of-the-art convnet architectures are not invariant to various appearance factors. In fact, all considered networks have similar weak points which cannot be mitigated by simply increasing the training data (architectural changes are needed). We show that overall performance can improve when using image renderings for data augmentation. We report the best known results on the Pascal3D+ detection and view-point estimation tasks

What can be learned about molecular reorientation from single molecule polarization microscopy?

We have developed a general approach for the calculation of the single molecule polarization correlation function C(t), which delivers a correlation of the emission dichroisms at time 0 and t. The approach is model independent and valid for general asymmetric top molecules. The key dynamic quantities of our analysis are the even-rank orientational correlation functions, the weighted sum of which yields C(t). We have demonstrated that the use of non-orthogonal schemes for the detection of the single molecule polarization responses makes it possible to manipulate the weighting coefficients in the expansion of C(t). Thus valuable information about the orientational correlation functions of the rank higher than second can be extracted from C(t)

Spontaneous soliton formation and modulational instability in Bose-Einstein condensates

The dynamics of an elongated attractive Bose-Einstein condensate in an axisymmetric harmonic trap is studied. It is shown that density fringes caused by self-interference of the condensate order parameter seed modulational instability. The latter has novel features in contradistinction to the usual homogeneous case known from nonlinear fiber optics. Several open questions in the interpretation of the recent creation of the first matter-wave bright soliton train [Strecker {\it et al.} Nature {\bf 417} 150 (2002)] are addressed. It is shown that primary transverse collapse, followed by secondary collapse induced by soliton--soliton interactions, produce bursts of hot atoms at different time scales.Comment: 4 pages, 3 figures. Phys. Rev. Lett. in pres