Publications

Using archival data of low-redshift (z < 0.01; Center for Astrophysics and SUSPECT databases) Type Ia supernovae (SNe Ia) and recent observations of high-redshift (0.16 < z < 0.64) SNe Ia, we study the "uniformity" of the spectroscopic properties of nearby and distant SNe Ia. We find no difference in the measurements we describe here. In this paper we base our analysis solely on line-profile morphology, focusing on measurements of the velocity location of maximum absorption (v abs) and peak emission (v peak). Our measurement technique makes it easier to compare low and high signal-to-noise ratio observations. We also quantify the associated sources of error, assessing the effect of line blending with assistance from the parameterized code SYNOW. We find that the evolution of v abs and v peak for our sample lines (Ca II λ3945, Si II λ6355, and S II λλ5454, 5640) is similar for both the low- and high-redshift samples. We find that v abs for the weak S II λλ5454, 5640 lines and v peak for S II λ5454 can be used to identify fast-declining [Δm 15(B) > 1.7] SNe Ia, which are also subluminous. In addition, we give the first direct evidence in two high-z SN Ia spectra of a double-absorption feature in Ca II λ3945, an event also observed, although infrequently, in low-redshift SN Ia spectra (6 out of 22 SNe Ia in our local sample). Moreover, echoing the recent studies of Dessart & Hillier in the context of Type II supernovae (SNe II), we see similar P Cygni line profiles in our large sample of SN Ia spectra. First, the magnitude of the velocity location at maximum profile absorption may underestimate that at the continuum photosphere, as observed, for example, in the optically thinner line S II λ5640. Second, we report for the first time the unambiguous and systematic intrinsic blueshift of peak emission of optical P Cygni line profiles in SN Ia spectra, by as much as 8000 km s -1. All the high-z SNe Ia analyzed in this paper were discovered and followed up by the ESSENCE collaboration and are now publicly available.

Oxidative stress is a host defense strategy to control bacterial infections, and bacteria have evolved systems to counteract this innate immune defense. Here, we investigate the peptide methionine sulfoxide reductase system in Staphylococcus aureus that repairs oxidized methionine residues in proteins, preventing the need to resynthesize damaged proteins de novo .

Multichannel electroencephalograms (EEGs) are processed using time-frequency (TF) analysis and synthesis techniques to geometrically localize neuroelectric generators of specific activity contained within the observed EEG. The TF domain techniques are utilized to separate the signals of interest from the remainder of the EEG, by allowing the definition of regions of interest which contain the signals for which we desire to localize the underlying neuronal generators. This approach essentially introduces a filtering technique which allows the distortionless separation of the signals of interest from all other components recorded. The source of the functional activity in the brain is estimated and mapped numerically by a least-squares approach. We have applied these techniques to identify the anatomical location of the sleep spindle, a component of the EEG observed during sleep, which is of importance in understanding the generation of sleep and sleep patterns.

article Share on Taming IP packet flooding attacks Authors: Karthik Lakshminarayanan UC Berkeley UC BerkeleyView Profile , Daniel Adkins UC Berkeley UC BerkeleyView Profile , Adrian Perrig CMU CMUView Profile , Ion Stoica UC Berkeley UC BerkeleyView Profile Authors Info & Claims ACM SIGCOMM Computer Communication ReviewVolume 34Issue 1January 2004 pp 45–50https://doi.org/10.1145/972374.972383Published:01 January 2004Publication History 38citation890DownloadsMetricsTotal Citations38Total Downloads890Last 12 Months17Last 6 weeks3 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

J. Sep. Sci. 2015, 38, 3262-3270 DOI: 10.1002/jssc.201500551 This cover picture illustrates an inter-laboratory study on the robustness and portability of capillary electrophoresis-mass spectrometry that is presented in this issue. Thirteen independent laboratories located around the globe as indicated on the map were participating in this study. The sheath-flow capillary electrophoresis-mass spectrometry interface used by most participating groups is depicted schematically on the right hand side. Migration time, peak height and peak area of 10 representative target peptides of a trypsin-digested protein sample were determined by every laboratory. The figures in the middle and left hand side show the final results obtained for means, repeatability (precision within a laboratory) and reproducibility (precision between laboratories). This study demonstrates that capillary electrophoresis-mass spectrometry is robust enough to allow a method transfer across multiple laboratories and should promote a more widespread use of this technology in biopharmaceutical analysis and related fields.

Datacenter disaggregation provides numerous benefits to both the datacenter operator and the application designer. However switching from the server-centric model to a disaggregated model requires developing new programming abstractions that can achieve high performance while benefiting from the greater elasticity. To explore the limits of datacenter disaggregation, we study an application area that near-maximally benefits from current server-centric datacenters: dense linear algebra. We build NumPyWren, a system for linear algebra built on a disaggregated serverless programming model, and LAmbdaPACK, a companion domain-specific language designed for serverless execution of highly parallel linear algebra algorithms. We show that, for a number of linear algebra algorithms such as matrix multiply, singular value decomposition, Cholesky decomposition, and QR decomposition, NumPyWren's performance (completion time) is within a factor of 2 of optimized server-centric MPI implementations, and has up to 15% greater compute efficiency (total CPU-hours), while providing fault tolerance.

In article number 1400919, John A. Rogers and co-workers report a thin-film multijunction solar cell architecture employing low refractive index air gaps as interfaces. Experimental devices using such a scheme exhibit enhanced photon recycling processes, suggesting a new path to realize photo-voltaic devices that utilize the entire solar spectrum and approach the thermodynamic efficiency limits.

This study presents experimental and theoretical evidence for distorted ≡Ti–OH groups supported on amorphous SiO2 and examines the influence of distortion on the strength of adsorption of polar molecules. For the theoretical part of this effort, we developed a model for isolated ≡Si–OH or ≡Ti–OH groups on the surface of amorphous silica. The ≡M–OH group is represented by a T8–11 cluster surrounded by a T747 cluster representing the surrounding amorphous silica. The properties of the small cluster are described by high-level density functional theory (DFT) (i.e., the quantum mechanical (QM) region), whereas the large surroundings are represented by molecular mechanics (MM). The QM/MM model was validated by demonstrating that the predicted enthalpy of adsorption for seven polar molecules on ≡Si–OH groups agrees satisfactorily with experimentally measured values determined by microcalorimetry. We also found that enthalpies of adsorption on isolated ≡Si–OH groups determined from isotherms obtained by infrared (IR) spectroscopy agree very well with the microcalorimetric values. IR spectroscopy was then used to measure isotherms for pyridine adsorption to Lewis acidic Ti isolated ≡Ti–OH groups grafted to amorphous silica. The isosteric enthalpy of adsorption decreased in magnitude with increasing pyridine coverages up to a coverage of 15% and then remained relatively constant for higher coverages. QM/MM calculations made with our model revealed that the enthalpy of adsorption is proportional to the area of the triangular O–Ti–O facets of the ≡Ti–OH group to which pyridine is bound. ≡Ti–OH sites exhibiting facet areas consistent with those deduced from X-ray absorption spectroscopy (XAS/EXAFS) measurements bind pyridine with enthalpies of adsorption consistent with the observed plateau for pyridine coverage above 15%. Larger tetrahedral facet areas are required to explain the coverage-dependent enthalpies of adsorption below 15% coverage, evidencing distorted ≡Ti–OH structures. Distorted ≡Ti–OH sites are also qualitatively consistent with reduced-intensity pre-edge X-ray absorption near-edge structure (XANES) measurements reported in this study. Energy decomposition analysis (EDA) calculations were carried out to understand the underlying physical phenomenon governing the change in the enthalpies of adsorption pyridine as a function of tetrahedral facet area.

Something like the real thing Artificial metalloenzymes ideally combine the favorable properties of natural enzymes with the high efficiency of synthetic catalysts. Inserting new metal groups into existing native proteins, however, often leads to poorer overall catalytic efficiency. To break through this limitation, Dydio et al. replaced the iron in the heme group of cytochrome P450 with iridium and subjected it to directed evolution. The enzyme catalyzed a range of reactions with kinetics similar to those of the native enzyme. It was also able to functionalize fully unactivated C-H bonds, a reaction that previously has only been mediated by synthetic catalysts. Moreover, the artificial enzyme was stable across temperatures and scales that are used industrially. Science , this issue p. 102