Time lower bounds for nonadaptive turnstile streaming algorithms

We say a turnstile streaming algorithm is "non-adaptive" if, during updates, the memory cells written and read depend only on the index being updated and random coins tossed at the beginning of the stream (and not on the memory contents of the algorithm). Memory cells read during queries may be decided upon adaptively. All known turnstile streaming algorithms in the literature are non-adaptive. We prove the first non-trivial update time lower bounds for both randomized and deterministic turnstile streaming algorithms, which hold when the algorithms are non-adaptive. While there has been abundant success in proving space lower bounds, there have been no non-trivial update time lower bounds in the turnstile model. Our lower bounds hold against classically studied problems such as heavy hitters, point query, entropy estimation, and moment estimation. In some cases of deterministic algorithms, our lower bounds nearly match known upper bounds

The adsorption structure of furan on Pd(1 1 1)

The structure of molecular furan, C4H4O, on Pd(1 1 1) has been investigated by O K-edge near-edge X-ray absorption fine structure (NEXAFS) and C 1s scanned-energy mode photoelectron diffraction (PhD). NEXAFS shows the molecule to be adsorbed with the molecular plane close to parallel to the surface, a conclusion confirmed by the PhD analysis. Chemical-state specific C 1s PhD data were obtained for the two inequivalent C atoms in the furan, the α-C atoms adjacent to the O atom, and the β-C atoms bonded only to C atoms, but only the PhD modulations for the α-C emitters were of sufficiently large amplitude for detailed evaluation using multiple scattering calculations. This analysis shows the α-C atoms to be located approximately 0.6 Å off-atop surface Pd atoms with an associated C–Pd bondlength of 2.13 ± 0.03 Å. Two alternative local geometries consistent with the data place the O atom in off-atop or near-hollow locations, and for each of these local structures there are two equally-possible registries relative to the fcc and hcp hollow sites. The results are in good agreement with earlier density functional theory calculations which indicate that the fcc and hcp registries are equally probable, but the PhD results fail to distinguish the two distinct local bonding geometries

A structural study of a C3H3 species coadsorbed with CO on Pd(1 1 1)

The combination of chemical-state-specific C 1s scanned-energy mode photoelectron diffraction (PhD) and O K-edge near-edge X-ray absorption fine structure (NEXAFS) has been used to determine the local adsorption geometry of the coadsorbed C3H3 and CO species formed on Pd(1 1 1) by dissociation of molecular furan. CO is found to adopt the same geometry as in the Pd(1 1 1)c(4 × 2)-CO phase, occupying the two inequivalent three-fold coordinated hollow sites with the C–O axis perpendicular to the surface. C3H3 is found to lie with its molecular plane almost parallel to the surface, most probably with the two ‘outer’ C atoms in equivalent off-atop sites, although the PhD analysis formally fails to distinguish between two distinct local adsorption sites

The Significance of Splenomegaly in Tumour-Bearing Mice

of the spleen and lvmph nodes occurred in (15713R mice which received transplants that enlargemelit of an A-strain tumour, Sarcoma 1, towhich thev were not susceptible. Thev attributed this to an immunological re,-,ction, but did not offer any explanation of the fact that splenic and 1Vmph node enlargement occurred also in susceptible (Astrain) mice which received transplants of the same tumour. The present investigation began with the observation that splenic enlargement occurred regularlv in A-strain female mice with spontaneous mammary cancer, and also in female A-strain Pnd (A x ASW)F1 hvbrid mice bearing transplants of ati A-strain mammarv carCinoma, but not;-C.9 a rule in mice of non-susceptible strains which received similar transplants. We h,,ive gone on to study the phenomenon in iiiore detail, aiid in particular to det-ermine firstlv-%A-hether splenomegalv can be produced in susceptible mice with cell-free tumour textracts, and secondly, whether it occurs when the tumour is transplai-ited to animals which are normall

Photoelectron diffraction: from phenomenological demonstration to practical tool

The potential of photoelectron diffraction—exploiting the coherent interference of directly-emitted and elastically scattered components of the photoelectron wavefield emitted from a core level of a surface atom to obtain structural information—was first appreciated in the 1970s. The first demonstrations of the effect were published towards the end of that decade, but the method has now entered the mainstream armoury of surface structure determination. This short review has two objectives: First, to outline the way that the idea emerged and the way this evolved in my own collaboration with Neville Smith and his colleagues at Bell Labs in the early years: Second, to provide some insight into the current state-of-the art in application of (scanned-energy mode) photoelectron diffraction to address two key issue in quantitative surface structure determination, namely, complexity and precision. In this regard a particularly powerful aspect of photoelectron diffraction is its elemental and chemical-state specificity

Evidence of Loss of Tumour-specific Antigen on Repeatedly Transplanting a Tumour in the Strain of Origin

SPLENOMEGALY has often been observed in mice bearing tumour transplants, and can occur even when the tumour originated in an animal isogenic with the recipient. This may sometimes be due, as has been suggested, to associated infection, or to extra-medullary haemopoiesis resulting from tumour-induced anaemia (van Ebbenhorst Tengbergen and Muhlbock, 1958). In experiments reported previously from this laboratory, however, splenomegaly developed regularly in the absence of infection in A-strain mice which received transplants of a spontaneous A-strain mammary carcinoma, or of the same tumour after 1-5 passages each of 2-3 weeks ' duration, and as the histological findings were characteristic of immunological stimulation it was concluded that the tumour possessed one or more antigens which were not represented in normal A-strain tissues (Woodruff and Symes, 1962). Subsequently, a chance observation suggested that after many passages the tumour was no longer capable of eliciting splenomegaly in the A-strain, and the following experiments were designed to investigate the matter

The Effect of Rat Spleen Cells on Two Transplanted Mouse Tumours

IT was reported in a previous paper (Woodruff and Symes, 1962a) that the growth, in A-strain mice, of subcutaneous transplants of a mammary carcinoma which originated in this strain, could be greatly retarded, and the tumour could sometimes be completely destroyed, by giving a sublethal dose of whole body irradiation followed by an intravenous injection of allogeneic spleen cells from either a normal CBA mouse or a CBA mouse which had been immunized against the A-strain tumour. Due to the concomitant induction of graft-versus-host disease, however, these procedures sometimes resulted in early death of the treated animals while the growth of their tumours remained arrested. The present experiments are concerned with the effect of an intraperitoneal injection of heterogeneic spleen cells from normal or pre-immunized rats, preceded in some cases by sublethal whole body irradiation, on mice previously injected by the same route with the Landschutz ascites tumour or with a cell suspension prepared from an A-strain mammary carcinoma. Previous observations on the anti-tumour effect of heterogeneic cells have bee

The local adsorption structure of benzene on Si(001)-(2 × 1): a photoelectron diffraction investigation

Scanned-energy mode C 1s photoelectron diffraction has been used to investigate the local adsorption geometry of benzene on Si(001) at saturation coverage and room temperature. The results show that two different local bonding geometries coexist, namely the 'standard butterfly' (SB) and 'tilted bridge' (TB) forms, with a composition of 58 ± 29% of the SB species. Detailed structural parameter values are presented for both species including Si–C bond lengths. On the basis of published measurements of the rate of conversion of the SB to the TB form on this surface, we estimate that the timescale of our experiment is sufficient for achieving equilibrium, and in this case our results indicate that the difference in the Gibbs free energy of adsorption, ΔG(TB)−ΔG(SB), is in the range −0.023 to +0.049 eV. We suggest, however, that the relative concentration of the two species may also be influenced by a combination of steric effects influencing the kinetics, and a sensitivity of the adsorption energies of the adsorbed SB and TB forms to the nature of the surrounding benzene molecules