Large Quantum Superpositions and Interference of Massive Nanometer-Sized Objects

We propose a method to prepare and verify spatial quantum superpositions of a nanometer-sized object separated by distances of the order of its size. This method provides unprecedented bounds for objective collapse models of the wave function by merging techniques and insights from cavity quantum optomechanics and matter wave interferometry. An analysis and simulation of the experiment is performed taking into account standard sources of decoherence. We provide an operational parameter regime using present day and planned technology.Comment: 4 pages, 2 figures, to appear in PR

A high-reflectivity high-Q micromechanical Bragg-mirror

We report on the fabrication and characterization of a micromechanical oscillator consisting only of a free-standing dielectric Bragg mirror with high optical reflectivity and high mechanical quality. The fabrication technique is a hybrid approach involving laser ablation and dry etching. The mirror has a reflectivity of 99.6%, a mass of 400ng, and a mechanical quality factor Q of approximately 10^4. Using this micromirror in a Fabry Perot cavity, a finesse of 500 has been achieved. This is an important step towards designing tunable high-Q high-finesse cavities on chip.Comment: 3 pages, 2 figure

Tipologija i tehnologija dva suprotna ili usporedna metodološka pristupa

The authors are analysing the advantages and disadvantages of typological and technological approaches to the analysis of stone and ceramic artefacts. The concepts of typological and technological analysis are coexisting since the beginnings of prehistoric archaeology. Detailed concepts of palaeolithic typologies appeared in the fifties and the sixties. Later on begins a dispute between the authors supporting the so called typological concept and those being mainly interested in the technological study of stone material. The latter are emphasising the process of making tools, analysing all the debitage products and considering the tools only as the final result of a complex chain consisting of different stages of the raw material modification. The typological approach is a static one with the main goal to place finds in a chronological and cultural sequence. The technological approach is dynamic and tends to explain the behaviour of the ancient man and the social relations of prehistoric populations and groups through the reconstruction of the production process. Technology sometimes helps the cultural definition of archaeological material and might also complete the typological definition by showing the emergence of a particular artefact type. There is a difference between the technological production process of stone and ceramic products that is, considering the final product, mostly visible in the change of weight of the raw material. Production of stone material implies a reduction of the raw material while it is quite opposite with ceramic products, i.e. the raw material is being accumulated during the production of a ceramic object (Baumler 1995). Despite the obvious differences typology and technology are not opposed methodological approaches but rather parallel ones. Both methods should be used in the analysis of archaeological material since each has different goals. Thus there can be achieved a more complete interpretation of activities on a particular site as well as a more accurate reconstruction of different processes of prehistoric populations everyday life.Autori analiziraju prednosti i nedostatke tipološkog i tehnološkog metodološkog pristupa analizi litičkih i keramičkih artefakata. Tipološki pristup je statički pristup čiji je osnovni cilj stavljanje nalaza u krono-kulturološku sekvencu. Tehnološki pristup je dinamičan, te preko rekonstrukcije procesa proizvodnje isčitava ponašanje davnašnjeg čovjeka i socijalne odnose prapovijesnih populacija ili skupina. Unatoč vidnim razlikama tipologija i tehnologija nisu suprotstavljeni metodološki pristupi. Oba pristupa valja koristiti pri analizi arheološkog materijala

Self-cooling of a micro-mirror by radiation pressure

We demonstrate passive feedback cooling of a mechanical resonator based on radiation pressure forces and assisted by photothermal forces in a high-finesse optical cavity. The resonator is a free-standing high-reflectance micro-mirror (of mass m=400ng and mechanical quality factor Q=10^4) that is used as back-mirror in a detuned Fabry-Perot cavity of optical finesse F=500. We observe an increased damping in the dynamics of the mechanical oscillator by a factor of 30 and a corresponding cooling of the oscillator modes below 10 K starting from room temperature. This effect is an important ingredient for recently proposed schemes to prepare quantum entanglement of macroscopic mechanical oscillators.Comment: 11 pages, 9 figures, minor correction

Novel resistance to imipenem associated with an altered PBP-4 in a Pseudomonas aeruginosa clinical isolate

A Pseudomonas aeruginosa (isolate 416) from a patient with pneumonia, was initially susceptible to imipenem (MIC: 2 mg/l) but became resistant to this antibiotic (isolate 470, MIC: 32 mg/l) during imipenem therapy. Treatment failed. No parallel increases in MIC were observed for other antimicrobials tested. Isolates 416 and 470 shared the same pyocin type and serotype, produced small amounts of an inducible β-lactamase, and had similar lipopolysaccharide compositions. On electrophoresis of outer membrane proteins, the porin F, identified by the monoclonal antibody MA4-4, was expressed similarly by the two isolates but the production of one band (apparent molecular weight 47,000) was diminished in isolate 470. [14C]-Imipenem labelling of intact cells proceeded more slowly in 470 than in 416, especially when bacterial cells were treated by antibody MA4-4 to block the porin F channel. [14C]-Imipenem labelling of penicillin binding proteins (PBP) showed that the band identified as PBP-4 bound markedly less radioactivity in isolate 470 than in 416. After isolate 470 was passaged several times in antibiotic-free broth, the imipenem MIC was decreased from 32 to 8 mg/l, and the [14C]-imipenem PBP pattern recovered the initial profile as exhibited by isolate 416. Two resistance mechanisms, affecting imipenem electively, could have combined their effect in the post-therapy isolate, altered target protein and reduced permeabilit

Changes of the Atlantic meridional overturning circulation of the past 30ka recorded in a depth transect at the Blake Outer Ridge

Oceans and climate are a tightly coupled system interacting with each other in various ways such as storage of carbon dioxide in the deep ocean. Within the global conveyor belt the Atlantic Meridional Overturning Circulation (AMOC) holds a key function, transporting warm salty surface waters from the tropical to the northern Atlantic where deep water formation takes place. Following the continental rise of North America this newly formed deep water propagates southward as Western Boundary Undercurrent (WBUC) ventilating the deep Atlantic. In the past (e.g. the last glacial cycle) strength and geometry of the AMOC have changed significantly. This study aims to provide a better understanding of the temporal and spatial (also depth depended) evolution of the AMOC in the western Atlantic sector since the last glacial (∼30 ka). We have investigated four sediment cores of the Blake Outer Ridge (30°N, 74°W; ODP 1059 to 1062) in a depth transect from 3000 to 4700 m water depth in the main flow path of the WBUC. We measured four down-core profiles of neodymium (εNd) and 231Pa/230Th isotopes for the reconstruction of water mass provenance and circulation strength of the last ∼30 ka. In contrast to published Nd isotope and 231Pa/230Th records from the Blake Ridge area our records are of unprecedented resolution, resolving climate key features of the North Atlantic region: Heinrich Stadials (HS) 1 and 2, the Last Glacial Maximum (LGM), the Bølling-Allerød and Younger Dryas (YD). Radiogenic Nd isotope signatures during the LGM reveal AABW to be the prevalent water mass in the deep western North Atlantic. The trend to more unradiogenic signatures during the deglaciation point to an increased formation of NADW which was again replaced by AABW during YD. The Holocene shows the most unradiogenic signatures and therefore established NADW. The circulation strength-proxy 231Pa/230Th indicates reduced LGM deep circulation, a pronounced slowdown during HS1 and a strong and deep circulation during the Holocene. Compared to isotopic records from the Bermuda Rise (ODP 1063) we found depth depended geometry changes of the WBUC which have occurred through the last glacial. Here, we focus on how deep northern sourced water has reached during phases of reduced circulation (indicated by increased 231Pa/230Th ratios) and the timing of this southward progradation of lower NADW

Campylobacter jejuni strains from patients with Guillain-Barré syndrome.

Guillain-Barré syndrome (GBS), an acute demyelinating peripheral neuropathy, may be triggered by an acute infectious illness; infection with Campylobacter jejuni is the most frequently reported antecedent event. In Japan, O:19 is the most common serotype among GBS-associated C. jejuni strains. To determine whether serotype O:19 occurs among GBS-associated strains in the United States and Europe, we serotyped seven such strains and found that two (29%) of seven GBS-associated strains from patients in the United States and Germany were serotype O:19. To determine whether GBS-associated strains may be resistant to killing by normal human serum (NHS), we studied the serum susceptibility of 17 GBS- and 27 enteritis-associated strains (including many O:19 and non-O:19 strains) using C. jejuni antibody positive (pool 1) or negative (pool 2) human serum. Using pool 1 serum we found that one (6%) of 18 serotype O:19 strains compared with 11 (42%) of 26 non-O:19 strains were killed; results using pool 2 serum were nearly identical. Finally, 8 O:19 and 8 non-O:19 strains were not significantly different in their ability to bind complement component C3. Serotype O:19 C. jejuni strains were overrepresented among GBS-associated strains in the United States and Germany and were significantly more serum-resistant than non-O:19 strains. The mechanism of this resistance appears unrelated to C3 binding

Phenomenology of the Equivalence Principle with Light Scalars

Light scalar particles with couplings of sub-gravitational strength, which can generically be called 'dilatons', can produce violations of the equivalence principle. However, in order to understand experimental sensitivities one must know the coupling of these scalars to atomic systems. We report here on a study of the required couplings. We give a general Lagrangian with five independent dilaton parameters and calculate the "dilaton charge" of atomic systems for each of these. Two combinations are particularly important. One is due to the variations in the nuclear binding energy, with a sensitivity scaling with the atomic number as $A^{-1/3}$. The other is due to electromagnetism. We compare limits on the dilaton parameters from existing experiments.Comment: 5 page

Northern Sourced Water dominated the Atlantic Ocean during the Last Glacial Maximum

Increased carbon sequestration in the ocean subsurface is commonly assumed to have been one of the main causes responsible for lower glacial atmospheric CO2 concentrations. Remineralized carbon must have been stored away from the atmosphere for thousands of years, yet the water mass structure accommodating such increased carbon storage continues to be debated. Here, we present new sediment-derived bottom-water neodymium isotope records that allow fingerprinting of water masses and provide a more complete picture of the Atlantic Meridional Overturning Circulation geometry during the Last Glacial Maximum. These results suggest that the vertical and meridional structure of the Atlantic water mass distribution only experienced minor changes since the last ice age. In particular, we find no compelling evidence supporting glacial southern-sourced water substantially expanding to shallower depths and farther into the Northern Hemisphere than today, which had been previously inferred from stable carbon isotope (δ13C) reconstructions. We argue that depleted δ13C values observed in the deep Northwest Atlantic do not necessarily indicate the presence of southern-sourced water. Instead, these values may represent a northern-sourced water mass with lower than modern preformed δ13C values that were further modified downstream by increased sequestration of remineralized carbon, facilitated by a more sluggish glacial deep circulation, corroborating previous evidence