1,109 research outputs found
Natufian Bone Artefacts from Nahal Oren, Mt. Carmel, Israel
No full textNahal Oren is a large Late Natufian site, which mostly served as a burial ground. Two series of excavations were conducted on this site providing a plethora of material remains. This article deals with the bone artefact assemblage from the fi rst series of excavations on the terrace. Lack of data pertaining to stratigraphic and spatial distribution of the bone items, as well as no data concerning the faunal assemblage, permits only a basic typological analysis of the bone artefacts. The assemblage comprises 90 items that generally accord typologically with other Natufian bone artefact assemblages reported in the literature. At the same time, some characteristics are evaluated and discussed herein.Nahal Oren est un site étendu du Natoufien final, principalement à vocation funéraire. Deux opérations de fouilles archéologiques ont été conduites ; elles ont fourni une grande quantité de mobilier. Cet article traite du matériel osseux issu des premières campagnes de fouille réalisées sur la terrasse. En raison des données lacunaires concernant la répartition stratigraphique et spatiale des objets en os et en l’absence d’informations sur les assemblages fauniques, seule une analyse typologique basique de l’outillage a été possible. La série comprend 90 pièces qui sont en grande partie analogues à celles des autres assemblages osseux du Natoufien déjà publiés. D’autre part, certaines de leurs caractéristiques sont ici discutées.Ashkenazy Hila, Belfer-Cohen Anna, Rabinovich Rivka. Natufian Bone Artefacts from Nahal Oren, Mt. Carmel, Israel. In: Paléorient, 2011, vol. 37, n°2. pp. 189-199
Prevention of Significant Deterioration: A Scalpel, Not an Axe
No full textDoes the United States need the Clean Air Act’s Prevention of Significant Deterioration (PSD) program to guard against degradation of air quality? In their recent Comment in these pages, John C. Evans and Donald van der Vaart say no, but the right answer is more nuanced. While the program is flawed in some respects, PSD helps to protect national parklands, guard against pollution “hot spots,” and decrease air pollution emission levels in the United States, thus helping to remedy regional pollution problems.Please direct any questions about this deposit to me as the authorized depositor
Struggling for Context: An Appraisal of “Struggling for Air”
No full textIn their recent book, Struggling for Air, Ricky Revesz and Jack Lienke argue that the Clean Air Act Amendments of 1970 contained a "tragic flaw": the failure to require national emissions standards for existing coal-fired power plants. They blame this flaw on a "missing of the mark," primarily by Senator Edmund Muskie, the chief Senate sponsor of the 1970 Amendments. I suggest instead that the technological and political context of the 1970 Amendments explains why the flaw exists, and that the failure to include national standards for coal-fired power plants is an error that can be seen only in retrospect.Please direct any questions about this deposit to me, as the authorized depositor. Thanks
Static vs. Adaptive Security in Perfect MPC: A Separation and the Adaptive Security of BGW
Full text linkAdaptive security is a highly desirable property in the design of secure protocols. It tolerates adversaries that corrupt parties as the protocol proceeds, as opposed to static security where the adversary corrupts the parties at the onset of the execution. The well-accepted folklore is that static and adaptive securities are equivalent for perfectly secure protocols. Indeed, this folklore is backed up with a transformation by Canetti et al. (EUROCRYPT'01), showing that any perfectly secure protocol that is statically secure and satisfies some basic requirements is also adaptively secure. Yet, the transformation results in an adaptively secure protocol with inefficient simulation (i.e., where the simulator might run in super-polynomial time even if the adversary runs just in polynomial time). Inefficient simulation is problematic when using the protocol as a sub-routine in the computational setting.
Our main question is whether an alternative efficient transformation from static to adaptive security exists. We show an inherent difficulty in achieving this goal generically. In contrast to the folklore, we present a protocol that is perfectly secure with efficient static simulation (therefore also adaptively secure with inefficient simulation), but for which efficient adaptive simulation does not exist (assuming the existence of one-way permutations).
In addition, we prove that the seminal protocol of Ben-Or, Goldwasser and Wigderson (STOC'88) is secure against adaptive, semi-honest corruptions with efficient simulation. Previously, adaptive security of the protocol, as is, was only known either for a restricted class of circuits, or for all circuits but with inefficient simulation
Three-Dimensional Spatiotemporal Pulse-Train Solitons
No full textExperimental realization of three-dimensional spatiotemporal solitons, which were proposed several decades ago, is still considered a “grand challenge” in nonlinear science. Here, we present experimental observation of 3D optical spatiotemporal pulse-train solitons. A spatially bright temporally dark pulse-train beam is trapped in a bulk medium that supports two types of nonlinearities: slowly responding saturable self-focusing that collectively self-trap the beam in the transverse directions and fast self-phase modulation that self-localizes each dark notch temporally (longitudinally). This work opens the possibility for experimental investigations of various soliton phenomena, including soliton interaction in 3D, formation of multimode spatiotemporal solitons, and envisioning new entities like partially coherent spatiotemporal solitons
Dataset for "selection rules in symmetry-broken systems by symmetries in synthetic dimensions"
No full text<p>Data for the article "Selection rules in symmetry-broken systems by symmetries in synthetic dimensions" by Matan Even Tzur, Ofer Neufeld, Eliyahu Bordo, Avner Fleischer, and Oren Cohen.</p>
Error Reduction for Weighted PRGs Against Read Once Branching Programs
Full text linkWeighted pseudorandom generators (WPRGs), introduced by Braverman, Cohen and Garg [Braverman et al., 2020], are a generalization of pseudorandom generators (PRGs) in which arbitrary real weights are considered, rather than a probability mass. Braverman et al. constructed WPRGs against read once branching programs (ROBPs) with near-optimal dependence on the error parameter. Chattopadhyay and Liao [Eshan Chattopadhyay and Jyun-Jie Liao, 2020] somewhat simplified the technically involved BCG construction, also obtaining some improvement in parameters.
In this work we devise an error reduction procedure for PRGs against ROBPs. More precisely, our procedure transforms any PRG against length n width w ROBP with error 1/poly(n) having seed length s to a WPRG with seed length s + O(logw/(ε) ⋅ log log1/(ε)). By instantiating our procedure with Nisan’s PRG [Noam Nisan, 1992] we obtain a WPRG with seed length O(log{n} ⋅ log(nw) + logw/(ε) ⋅ log log 1/(ε)). This improves upon [Braverman et al., 2020] and is incomparable with [Eshan Chattopadhyay and Jyun-Jie Liao, 2020].
Our construction is significantly simpler on the technical side and is conceptually cleaner. Another advantage of our construction is its low space complexity O(log{nw})+poly(log log1/(ε)) which is logarithmic in n for interesting values of the error parameter ε. Previous constructions (like [Braverman et al., 2020; Eshan Chattopadhyay and Jyun-Jie Liao, 2020]) specify the seed length but not the space complexity, though it is plausible they can also achieve such (or close) space complexity
Interlocked attosecond pulse trains in slightly bi-elliptical high harmonic generation
No full textAbstractThe ellipticity of high harmonics driven by bi-chromatic (e.g. ω−2ω) co-propagating fields can be fully tuned by varying the polarization of the pump components. In order to start revealing the underlying mechanism of this control, we explore a relatively simple regime of this scheme that still gives rise to full control over the harmonics ellipticities. In this regime, the pumps are only slightly elliptical and the high harmonic radiation consists of two (different) interlocked attosecond pulse trains (APTs). We formulate a semi-analytic model that maps the high harmonic ellipticity to properties of the APTs harmonic decompositions. Utilizing this model, we reconstruct these APTs variables from measurements of the high harmonics ellipticities. This ellipticity-resolved spectroscopy of interlocked APTs may be useful for ultrafast probing of chiral degrees of freedom
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