ABSTRACT
The Lévy flight foraging hypothesis states that organisms must have evolved adaptations to exploit Lévy walk search strategies. Indeed, it is widely accepted that inverse square Lévy walks optimize the search efficiency in foraging with unrestricted revisits (also known as nondestructive foraging). However, a mathematically rigorous demonstration of this for dimensions D≥2 is still lacking. Here we study the very closely related problem of a Lévy walker inside annuli or spherical shells with absorbing boundaries. In the limit that corresponds to the foraging with unrestricted revisits, we show that inverse square Lévy walks optimize the search. This constitutes the strongest formal result to date supporting the optimality of inverse square Lévy walks search strategies.
ABSTRACT
Dominating finite-range interactions in many-body systems can lead to intriguing self-ordered phases of matter. For quantum magnets, Ising models with power-law interactions are among the most elementary systems that support such phases. These models can be implemented by laser coupling ensembles of ultracold atoms to Rydberg states. Here, we report on the experimental preparation of crystalline ground states of such spin systems. We observe a magnetization staircase as a function of the system size and show directly the emergence of crystalline states with vanishing susceptibility. Our results demonstrate the precise control of Rydberg many-body systems and may enable future studies of phase transitions and quantum correlations in interacting quantum magnets.
ABSTRACT
Telepathology usage in the past has typically been a qualitative procedure rather than a quantitative measurement. DNA ploidy using image analysis has been favorably compared to DNA ploidy analysis by flow cytometry in numerous publications. A step from DNA ploidy analysis using conventional image analysis to DNA ploidy analysis using stored images allows DNA ploidy analysis by image cytometry to become a powerful tool in telepathology. Remote DNA ploidy analysis using stored images has an impact on the field of pathology, as not every hospital or laboratory can afford to perform this type of specialized testing. However, images have large data files and require lengthy transmission times over communication systems to other computers. Joint Photographer Experts Group (JPEG) compression is a computer algorithm that allows the file size of an image to be reduced in order to decrease transmission times to another computer. A study was initiated to investigate the effects of JPEG compression on images of Feulgen stained breast tumor touch preps and the resulting DNA ploidy histograms.
Subject(s)
Breast Neoplasms/genetics , DNA/analysis , Ploidies , Software , Telepathology/instrumentation , Telepathology/methods , Animals , Humans , Liver/cytology , RatsABSTRACT
More than 40 years ago, Andreev, Lifshitz and Chester suggested the possible existence of a peculiar solid phase of matter, the microscopic constituents of which can flow superfluidly without resistance due to the formation of zero-point defects in the ground state of self-assembled crystals. Yet, a physical system where this mechanism is unambiguously established remains to be found, both experimentally and theoretically. Here we investigate the zero-temperature phase diagram of two-dimensional bosons with finite-range soft-core interactions. For low particle densities, the system is shown to feature a solid phase in which zero-point vacancies emerge spontaneously and give rise to superfluid flow of particles through the crystal. This provides the first example of defect-induced, continuous-space supersolidity consistent with the Andreev-Lifshitz-Chester scenario.
ABSTRACT
JPEG compression can be used on images for DNA ploidy analysis if careful consideration is given to the level of compression used for file storage. The amount of JPEG compression possible may vary depending on the type of tissue analyzed, however, a compromise may be reached for all types of tissue. JPEG compression should not go over a level of 70 for DNA analysis as this would result in possibly erroneous IOD calculation and erroneous DNA ploidy analysis. Also, the resulting file quality is so poor that even visual analysis is not possible. With careful training of personnel in cell selection, remote DNA ploidy analysis would be an effective tool for standardization and quality control in the pathology laboratory. By using remote DNA ploidy analysis, it is possible for hospitals to consolidate their workload, and make DNA ploidy analysis by image cytometry a cost effective test in the laboratory. Proficiency testing would also become possible as all laboratories performing DNA ploidy analysis would receive the same fields of view for testing. DNA ploidy analysis by image cytometry using stored images could be a versatile tool for the telepathology community.