34,721 research outputs found
The National Security Agency\u27s Domestic Spying Program: Framing the Debate
On Friday, December 16, 2005, the New York Times reported that President George W. Bush had secretly authorized the National Security Agency (NSA) to conduct warrantless surveillance of Americans\u27 telephone and e-mail communications as part of an effort to obtain intelligence about future terrorist activity.\u27 The Times report was based on leaks of classified information, presumably by NSA officials concerned about the legality of the program. The Times reported that at the President\u27s request it had delayed publication of the story for more than a year.
The Indiana Law Journal reprinted four documents that, taken together, set forth the basic arguments concerning the lawfulness of the secret NSA surveillance program. The debate outlined by the four documents raises important issues about statutory interpretation in the face of claims of constitutional conflict, executive power during times of war, fundamental privacy rights of Americans, and ultimately, the rule of law in the war on terror
Characterization and In-situ Monitoring of Sub-stoichiometric Adjustable Tc Titanium Nitride Growth
The structural and electrical properties of Ti-N films deposited by reactive
sputtering depend on their growth parameters, in particular the Ar:N2 gas
ratio. We show that the nitrogen percentage changes the crystallographic phase
of the film progressively from pure \alpha-Ti, through an \alpha-Ti phase with
interstitial nitrogen, to stoichiometric Ti2N, and through a substoichiometric
TiNX to stoichiometric TiN. These changes also affect the superconducting
transition temperature, Tc, allowing, the superconducting properties to be
tailored for specific applications. After decreasing from a Tc of 0.4 K for
pure Ti down to below 50 mK at the Ti2N point, the Tc then increases rapidly up
to nearly 5 K over a narrow range of nitrogen incorporation. This very sharp
increase of Tc makes it difficult to control the properties of the film from
wafer-to-wafer as well as across a given wafer to within acceptable margins for
device fabrication. Here we show that the nitrogen composition and hence the
superconductive properties are related to, and can be determined by,
spectroscopic ellipsometry. Therefore, this technique may be used for process
control and wafer screening prior to investing time in processing devices
Phosphorus and arsenic distributions in a seasonally-stratified, iron- and manganese-rich lake: microbiological and geochemical controls
Seasonal stratification in temperate lakes greater than a few metres deep provides conditions amenable to pronounced vertical zonation of redox chemistry. Such changes are particularly evident in eutrophic systems where high phytoplankton biomass often leads to seasonally-established anoxic hypolimnia and profound changes in geochemical conditions. In this study, we investigated the behaviour of trace elements in the water column of a seasonally-stratified, eutrophic lake. Two consecutive years of data from Lake Ngapouri, North Island, New Zealand, demonstrate the occurrence of highly correlated profiles of phosphorus (P), arsenic (As), iron (Fe) and manganese (Mn), all of which increased in concentration by 1-2 orders of magnitude within the anoxic hypolimnion. Stoichiometric and mass-balance considerations demonstrate that increases in alkalinity in hypolimnetic waters were consistent with observed changes in sulfate, Fe and Mn concentrations with depth, corresponding to dissimilatory reduction of sulfate, Fe(III) and Mn(IV) hydroxides. Thermodynamic constraints on Fe, Mn and Al solubility indicate that amorphous Fe(III), Mn(IV) hydroxides most probably controlled Fe and Mn in the surface mixed layer (~0 to 8 m) while Al(III) hydroxides were supersaturated throughout the entire system. Surface complexation modelling indicated that iron hydroxides (HFO) potentially dominated As speciation in the lake. It is likely that other colloidal phases such as allophanic clays also limited HPO42- activity, reducing competition for HAsO42- adsorption to iron hydroxides. This research highlights the coupling of P, As, Fe and Mn in Lake Ngapouri, and the apparent role of multiple colloidal phases in affecting P and As activity within overarching microbiological and geochemical processes
Etch Induced Microwave Losses in Titanium Nitride Superconducting Resonators
We have investigated the correlation between the microwave loss and
patterning method for coplanar waveguide titanium nitride resonators fabricated
on Si wafers. Three different methods were investigated: fluorine- and
chlorine-based reactive ion etches and an argon-ion mill. At high microwave
probe powers the reactive etched resonators showed low internal loss, whereas
the ion-milled samples showed dramatically higher loss. At single-photon powers
we found that the fluorine-etched resonators exhibited substantially lower loss
than the chlorine-etched ones. We interpret the results by use of numerically
calculated filling factors and find that the silicon surface exhibits a higher
loss when chlorine-etched than when fluorine-etched. We also find from
microscopy that re-deposition of silicon onto the photoresist and side walls is
the probable cause for the high loss observed for the ion-milled resonator
Coherence in a transmon qubit with epitaxial tunnel junctions
We developed transmon qubits based on epitaxial tunnel junctions and
interdigitated capacitors. This multileveled qubit, patterned by use of
all-optical lithography, is a step towards scalable qubits with a high
integration density. The relaxation time T1 is .72-.86mu sec and the ensemble
dephasing time T2 is slightly larger than T1. The dephasing time T2 (1.36mu
sec) is nearly energy-relaxation-limited. Qubit spectroscopy yields weaker
level splitting than observed in qubits with amorphous barriers in
equivalent-size junctions. The qubit's inferred microwave loss closely matches
the weighted losses of the individual elements (junction, wiring dielectric,
and interdigitated capacitor), determined by independent resonator
measurements
The gauge structure of generalised diffeomorphisms
We investigate the generalised diffeomorphisms in M-theory, which are gauge
transformations unifying diffeomorphisms and tensor gauge transformations.
After giving an En(n)-covariant description of the gauge transformations and
their commutators, we show that the gauge algebra is infinitely reducible,
i.e., the tower of ghosts for ghosts is infinite. The Jacobiator of generalised
diffeomorphisms gives such a reducibility transformation. We give a concrete
description of the ghost structure, and demonstrate that the infinite sums give
the correct (regularised) number of degrees of freedom. The ghost towers belong
to the sequences of rep- resentations previously observed appearing in tensor
hierarchies and Borcherds algebras. All calculations rely on the section
condition, which we reformulate as a linear condition on the cotangent
directions. The analysis holds for n < 8. At n = 8, where the dual gravity
field becomes relevant, the natural guess for the gauge parameter and its
reducibility still yields the correct counting of gauge parameters.Comment: 24 pp., plain tex, 1 figure. v2: minor changes, including a few added
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