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Structures of the linear silicon carbides SiC 4 and SiC 6 : Isotopic substitution and Ab Initio theory
V. D. Gordon,a) E. S. Nathan, A. J. Apponi, M. C. McCarthy, and P. Thaddeus are with
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 and
Division of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge,
Massachusetts 02138
-- P. Botschwina is with the
Institut fu¨r Physikalische Chemie der Universita¨t Go¨ttingen, Tammannstr, 6. D-37077 Go¨ttingen, GermanyThe structures of two linear silicon carbides, SiC4 and SiC6, have been determined by a combination
of isotopic substitution and large-scale coupled-cluster ab initio calculations, following detection of
all of the singly substituted isotopic species in a supersonic molecular beam with a Fourier transform
microwave spectrometer. Rotational constants obtained by least-squares fitting transition
frequencies were used to derive experimental structures; except for those nearest the center of mass,
individual bond lengths for both chains have an error of less than 0.008 Å. Accurate equilibrium
structures were derived by converting the experimental rotational constants to equilibrium constants
using the vibration–rotation coupling constants from coupled-cluster calculations, including
connected triple substitutions. Equilibrium dipole moments and harmonic vibrational frequencies
were also calculated for both chains. On the basis of the calculated vibration–rotation and l-type
doubling constants, weak rotational satellites from a low-lying vibrational state of SiC4 were
assigned to v6 , a bending mode calculated to lie about 205 cm -1 above the ground state. A
recommended ab initio equilibrium structure for SiC8 has also been established. © 2000 American
Institute of Physics. @S0021-9606~00!01537-3#Chemistr
Preserving Both Privacy and Utility in Network Trace Anonymization
As network security monitoring grows more sophisticated, there is an
increasing need for outsourcing such tasks to third-party analysts. However,
organizations are usually reluctant to share their network traces due to
privacy concerns over sensitive information, e.g., network and system
configuration, which may potentially be exploited for attacks. In cases where
data owners are convinced to share their network traces, the data are typically
subjected to certain anonymization techniques, e.g., CryptoPAn, which replaces
real IP addresses with prefix-preserving pseudonyms. However, most such
techniques either are vulnerable to adversaries with prior knowledge about some
network flows in the traces, or require heavy data sanitization or
perturbation, both of which may result in a significant loss of data utility.
In this paper, we aim to preserve both privacy and utility through shifting the
trade-off from between privacy and utility to between privacy and computational
cost. The key idea is for the analysts to generate and analyze multiple
anonymized views of the original network traces; those views are designed to be
sufficiently indistinguishable even to adversaries armed with prior knowledge,
which preserves the privacy, whereas one of the views will yield true analysis
results privately retrieved by the data owner, which preserves the utility. We
present the general approach and instantiate it based on CryptoPAn. We formally
analyze the privacy of our solution and experimentally evaluate it using real
network traces provided by a major ISP. The results show that our approach can
significantly reduce the level of information leakage (e.g., less than 1\% of
the information leaked by CryptoPAn) with comparable utility
Reef fishes weaken dietary preferences after coral mortality, altering resource overlap
The direct and indirect effects of climate change can affect, and are mediated by, changes in animal behaviour. However, we often lack sufficient empirical data to assess how large-scale disturbances affect the behaviour of individuals, which scales up to influence communities. Here, we investigate these patterns by focusing on the foraging behaviour of butterflyfishes, prominent coral-feeding fishes on coral reefs, before and after a mass coral bleaching event in Iriomote, Japan. In response to 65% coral mortality, coral-feeding fishes broadened their diets, showing a significant weakening of dietary preferences across species. Multiple species reduced their consumption of bleaching-sensitive Acropora corals, while expanding their diets to consume a variety of other coral genera. This resulted in decreased dietary overlap among butterflyfishes. Behavioural changes in response to bleaching may increase resilience of coral reef fishes in the short term. However, coral mortality has reduced populations of coral-feeders world-wide, indicating the changes in feeding behaviour we document here may not be sufficient to ensure long-term resilience of butterflyfishes on coral reefs
Epidemiological studies of Mansonella ozzardi (Nematoda, Onchocercidae) in indigenous communities of Pauini municipality, Amazonas, Brazil
Strings in a Time-Dependent Orbifold
We consider string theory in a time dependent orbifold with a null
singularity. The singularity separates a contracting universe from an expanding
universe, thus constituting a big crunch followed by a big bang. We quantize
the theory both in light-cone gauge and covariantly. We also compute some tree
and one loop amplitudes which exhibit interesting behavior near the
singularity. Our results are compatible with the possibility that strings can
pass through the singularity from the contracting to the expanding universe,
but they also indicate the need for further study of certain divergent
scattering amplitudes.Comment: 27 pages, minor changes and note adde
Effect of C-2 substitution on the stability of non-traditional cephalosporins in mouse plasma
A systematic study of the stability of a set of cephalosporins in mouse plasma reveals that cephalosporins lacking an acidic moiety at C-2 may be vulnerable to β-lactam cleavage in mouse plasma
Clinical predictors of 3- and 6-month outcome for mild traumatic brain injury patients with a negative head CT scan in the emergency department: A TRACK-TBI pilot study
Aconsiderable subset of mild traumatic brain injury (mTBI) patients fail to return to baseline functional status at or beyond 3 months postinjury. Identifying at-risk patients for poor outcome in the emergency department (ED) may improve surveillance strategies and referral to care. Subjects with mTBI (Glasgow Coma Scale 13–15) and negative ED initial head CT < 24 h of injury, completing 3- or 6-month functional outcome (Glasgow Outcome Scale-Extended; GOSE), were extracted from the prospective, multicenter Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) Pilot study. Outcomes were dichotomized to full recovery (GOSE = 8) vs functional deficits (GOSE < 8). Univariate predictors with p < 0.10 were considered for multivariable regression. Adjusted odds ratios (AOR) were reported for outcome predictors. Significance was assessed at p < 0.05. Subjects who completed GOSE at 3- and 6-month were 211 (GOSE < 8: 60%) and 185 (GOSE < 8: 65%). Risk factors for 6-month GOSE < 8 included less education (AOR = 0.85 per-year increase, 95% CI: (0.74–0.98)), prior psychiatric history (AOR = 3.75 (1.73–8.12)), Asian/minority race (American Indian/Alaskan/Hawaiian/Pacific Islander) (AOR = 23.99 (2.93–196.84)), and Hispanic ethnicity (AOR = 3.48 (1.29–9.37)). Risk factors for 3-month GOSE < 8 were similar with the addition of injury by assault predicting poorer outcome (AOR = 3.53 (1.17–10.63)). In mTBI patients seen in urban trauma center EDs with negative CT, education, injury by assault, Asian/minority race, and prior psychiatric history emerged as risk factors for prolonged disability
On the relative positions of the peaks in Raman and tunneling spectra of d-wave superconductors
We study Raman intensity and the density of states
in isotropic 2D d-wave superconductors. For an ideal gas,
and have sharp peaks at and , respectively, where is the maximum value of the gap.
We study how the peak positions are affected by the fermionic damping due to
impurity scattering.
We show that while the damping generally shifts the peak positions to larger
frequencies, the peak in still occurs at almost twice the peak
position in and therefore cannot account for the experimentally
observed downturn shift of the peak frequency in in underdoped
cuprates compared to twice that in . We also discuss how the
fermionic damping affects the dynamical spin susceptibility.Comment: 5 pages, 2 figure
Toxic effect of commercial formulations of neem oil, Azadirachta indica A. Juss., in pupae and adults of the sugarcane borer, Diatraea saccharalis F. (Lepidoptera: Crambidae)
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