Densest local packing diversity. II. Application to three dimensions

The densest local packings of N three-dimensional identical nonoverlapping spheres within a radius Rmin(N) of a fixed central sphere of the same size are obtained for selected values of N up to N = 1054. In the predecessor to this paper [A.B. Hopkins, F.H. Stillinger and S. Torquato, Phys. Rev. E 81 041305 (2010)], we described our method for finding the putative densest packings of N spheres in d-dimensional Euclidean space Rd and presented those packings in R2 for values of N up to N = 348. We analyze the properties and characteristics of the densest local packings in R3 and employ knowledge of the Rmin(N), using methods applicable in any d, to construct both a realizability condition for pair correlation functions of sphere packings and an upper bound on the maximal density of infinite sphere packings. In R3, we find wide variability in the densest local packings, including a multitude of packing symmetries such as perfect tetrahedral and imperfect icosahedral symmetry. We compare the densest local packings of N spheres near a central sphere to minimal-energy configurations of N+1 points interacting with short-range repulsive and long-range attractive pair potentials, e.g., 12-6 Lennard-Jones, and find that they are in general completely different, a result that has possible implications for nucleation theory. We also compare the densest local packings to finite subsets of stacking variants of the densest infinite packings in R3 (the Barlow packings) and find that the densest local packings are almost always most similar, as measured by a similarity metric, to the subsets of Barlow packings with the smallest number of coordination shells measured about a single central sphere, e.g., a subset of the FCC Barlow packing. We additionally observe that the densest local packings are dominated by the spheres arranged with centers at precisely distance Rmin(N) from the fixed sphere's center.Comment: 45 pages, 18 figures, 2 table

Succenturiate Placental Lobe Abruption: a placental pathology complicating a dangerous delivery

The development of a placenta is a complex process that occurs without a clinically significant issue in most pregnancies. At times, however, the process develops in a way that isolates an island of placental tissue away from the main body, connected only by unprotected vasculature within the amniotic membranes. The vessels of this succenturiate lobe of the placenta are vulnerable both to compression or laceration, threatening the antepartum period with poor weight gain or the peripartum period with fetal distress, hemorrhage or retained products of conception. A majority of the time, this pathology is undiagnosed until recognized innocuously following delivery of the placenta. A placental abruption is a premature separation of the placenta from the uterus that can result in painful bleeding and fetal distress. This increased distress of mother or baby from continued blood loss usually necessitates delivery either vaginally, if stability is maintained, or by cesarean if it isn’t. The amount of distress correlates to where and how much of the placenta is affected. While succenturiate lobes of the placenta and placental abruptions are not routinely associated with each other, the abruption of only the succenturiate lobe of the placenta in this instance minimized the severity to the fetus, by allowing the main body of the placenta to remain intact. As the bleeding coagulated at the lobe, maternal well-being was maintained allowing enough time to complete a vaginal delivery

In defense of the personal/impersonal distinction in moral psychology research: Cross-cultural validation of the dual process model of moral judgment

The dual process model of moral judgment (DPM; Greene et al., 2004) argues that such judgments are influenced by both emotion-laden intuition and controlled reasoning. These influences are associated with distinct neural circuitries and different response tendencies. After reanalyzing data from an earlier study, McGuire et al. (2009) questioned the level of support for the dual process model and asserted that the distinction between emotion evoking moral dilemmas (personal dilemmas) and those that do not trigger such intuitions (impersonal dilemmas) is spurious. Using similar reanalysis methods on data reported by Moore, Clark, and Kane (2008), we show that the personal/impersonal distinction is reliable. Furthermore, new data show that this distinction is fundamental to moral judgment across widely different cultures (U.S. and China) and supports claims made by the DPM

Dense sphere packings from optimized correlation functions

Elementary smooth functions (beyond contact) are employed to construct pair correlation functions that mimic jammed disordered sphere packings. Using the g2-invariant optimization method of Torquato and Stillinger [J. Phys. Chem. B 106, 8354, 2002], parameters in these functions are optimized under necessary realizability conditions to maximize the packing fraction phi and average number of contacts per sphere Z. A pair correlation function that incorporates the salient features of a disordered packing and that is smooth beyond contact is shown to permit a phi of 0.6850: this value represents a 45% reduction in the difference between the maximum for congruent hard spheres in three dimensions, pi/sqrt{18} ~ 0.7405, and 0.64, the approximate fraction associated with maximally random jammed (MRJ) packings in three dimensions. We show that, surprisingly, the continued addition of elementary functions consisting of smooth sinusoids decaying as r^{-4} permits packing fractions approaching pi/sqrt{18}. A translational order metric is used to discriminate between degrees of order in the packings presented. We find that to achieve higher packing fractions, the degree of order must increase, which is consistent with the results of a previous study [Torquato et al., Phys. Rev. Lett. 84, 2064, 2000].Comment: 26 pages, 9 figures, 1 table; added references, fixed typos, simplified argument and discussion in Section IV

Sintered Cr/Pt and Ni/Au ohmic contacts to B12P2

Citation: Frye, C. D., Kucheyev, S. O., Edgar, J. H., Voss, L. F., Conway, A. M., Shao, Q. H., & Nikolic, R. J. (2015). Sintered Cr/Pt and Ni/Au ohmic contacts to B12P2. Journal of Vacuum Science & Technology A, 33(3), 6. doi:10.1116/1.4917010Icosahedral boron phosphide (B12P2) is a wide-bandgap semiconductor possessing interesting properties such as high hardness, chemical inertness, and the reported ability to self-heal from irradiation by high energy electrons. Here, the authors developed Cr/Pt and Ni/Au ohmic contacts to epitaxially grown B12P2 for materials characterization and electronic device development. Cr/Pt contacts became ohmic after annealing at 700 degrees C for 30 s with a specific contact resistance of 2 x 10(-4) Omega cm(2), as measured by the linear transfer length method. Ni/Au contacts were ohmic prior to any annealing, and their minimum specific contact resistance was similar to l-4 x 10(-4) Omega cm(2) after annealing over the temperature range of 500-800 degrees C. Rutherford backscattering spectrometry revealed a strong reaction and intermixing between Cr/Pt and B12P2 at 700 degrees C and a reaction layer between Ni and B12P2 thinner than similar to 25 nm at 500 degrees C. (C) 2015 American Vacuum Society

Generalized Relativistic Meson Wave Function

We study the most general, relativistic, constituent $q{\overline q}$ meson wave function within a new covariant framework. We find that by including a tensor wave function component, a pure valence quark model is now capable of reproducing not only all static pion data ($f_\pi$, $\langle r_\pi^2 \rangle$) but also the distribution amplitude, form factor $(F_\pi(Q^2))$, and structure functions. Further, our generalized spin wave function provides a much better detailed description of meson properties than models using a simple relativistic extension of the $S=L=0$ nonrelativistic wave function.Comment: 17 pages, REXTeX 3.0 file, (uuencoded postscript files of 8 figures appended

Experience with telemedicine among rheumatology clinicians during the COVID-19 pandemic: an international survey

Objective: The aim was to assess rheumatology clinicians' perceptions of telemedicine and their experiences before and during the coronavirus disease 2019 (COVID-19) pandemic. Methods: We conducted a cross-sectional online survey and collected responses from rheumatology clinicians worldwide, between November 2020 and February 2021, regarding use and perceptions of telemedicine in rheumatology. We summarized data with descriptive statistics and qualitative analysis for free-text responses. Results: The survey was completed by 349 rheumatology clinicians from 49 countries; 59% were female and about two-thirds were in the 30-50 years age group. Academic affiliations were held by 55% of participants, and 44% were from North America. Before the pandemic, 24% of participants had experience with telemedicine, whereas about three-quarters used telemedicine for the first time during the pandemic. Overall, 56% thought they provided less adequate care with telemedicine. More than half of clinicians felt that telemedicine was adequate for evaluating crystalline arthritis, inflammatory arthritis and lupus flares. Telemedicine was felt to be inadequate for flares of myositis, vasculitis and scleroderma. Technical problems were reported in 29% of telemedicine encounters and were most commonly related to patient-encountered difficulties. Conclusion: Most rheumatology clinicians used telemedicine for the first time during the pandemic. The quality of care provided was thought to be inferior to that provided in person for specific clinical situations. Additional efforts are needed to address barriers to effective telemedicine, such as patient-related technology issues, challenges with building rapport and performing a physical examination, and to define the appropriate scope of clinical scenarios conducive to telemedicine

Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV

A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 inverse femtobarns. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.Comment: Submitted to JHE

Combined search for the quarks of a sequential fourth generation

Results are presented from a search for a fourth generation of quarks produced singly or in pairs in a data set corresponding to an integrated luminosity of 5 inverse femtobarns recorded by the CMS experiment at the LHC in 2011. A novel strategy has been developed for a combined search for quarks of the up and down type in decay channels with at least one isolated muon or electron. Limits on the mass of the fourth-generation quarks and the relevant Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a simple extension of the standard model with a sequential fourth generation of fermions. The existence of mass-degenerate fourth-generation quarks with masses below 685 GeV is excluded at 95% confidence level for minimal off-diagonal mixing between the third- and the fourth-generation quarks. With a mass difference of 25 GeV between the quark masses, the obtained limit on the masses of the fourth-generation quarks shifts by about +/- 20 GeV. These results significantly reduce the allowed parameter space for a fourth generation of fermions.Comment: Replaced with published version. Added journal reference and DO