Reactive ion etching of Ta–Si–N diffusion barriers in CF_(4)+O_(2)

Ta_(36)Si_(14)N_(50) amorphous layers were reactive ion etched in CF_(4)+O_(2) plasmas. The etch depth was determined as a function of gas composition, pressure, and cathode power. Adding small amounts of O_2 to CF_4 increased the etch rates up to approximately 15% O_2 concentration, with etch rates then decreasing with further addition of O_2. Etch rates increased with both pressure and power. Etching proceeded only after an initial delay time which depended upon gas composition and power. The delay is probably caused by a surface native oxide which must be removed before etching can commence. The presence of a surface oxide was observed from Auger electron spectroscopy intensity depth profile measurements and is estimated to be 2 nm thick. Under optimal conditions, the etch rate of Ta_(36)Si_(14)N_(50) is about seven times higher than for SiO_2, thus providing a high degree of selectivity for integrated circuit processing

Optical-Model Description of Time-Reversal Violation

A time-reversal-violating spin-correlation coefficient in the total cross section for polarized neutrons incident on a tensor rank-2 polarized target is calculated by assuming a time-reversal-noninvariant, parity-conserving ``five-fold" interaction in the neutron-nucleus optical potential. Results are presented for the system $n + {^{165}{\rm Ho}}$ for neutron incident energies covering the range 1--20 MeV. From existing experimental bounds, a strength of $2 \pm 10$ keV is deduced for the real and imaginary parts of the five-fold term, which implies an upper bound of order $10^{-4}$ on the relative $T$-odd strength when compared to the central real optical potential.Comment: 11 pages (Revtex

The angular distribution of the reaction νˉe+p→e++n\bar{\nu}_e + p \to e^+ + n

The reaction $\bar{\nu}_e + p \to e^+ + n$ is very important for low-energy ($E_\nu \lesssim 60$ MeV) antineutrino experiments. In this paper we calculate the positron angular distribution, which at low energies is slightly backward. We show that weak magnetism and recoil corrections have a large effect on the angular distribution, making it isotropic at about 15 MeV and slightly forward at higher energies. We also show that the behavior of the cross section and the angular distribution can be well-understood analytically for $E_\nu \lesssim 60$ MeV by calculating to ${\cal O}(1/M)$, where $M$ is the nucleon mass. The correct angular distribution is useful for separating $\bar{\nu}_e + p \to e^+ + n$ events from other reactions and detector backgrounds, as well as for possible localization of the source (e.g., a supernova) direction. We comment on how similar corrections appear for the lepton angular distributions in the deuteron breakup reactions $\bar{\nu}_e + d \to e^+ + n + n$ and $\nu_e + d \to e^- + p + p$. Finally, in the reaction $\bar{\nu}_e + p \to e^+ + n$, the angular distribution of the outgoing neutrons is strongly forward-peaked, leading to a measurable separation in positron and neutron detection points, also potentially useful for rejecting backgrounds or locating the source direction.Comment: 10 pages, including 5 figure

The Ty1 integrase protein can exploit the classical nuclear protein import machinery for entry into the nucleus

Like its retroviral relatives, the long terminal repeat retrotransposon Ty1 in the yeast Saccharomyces cerevisiae must traverse a permanently intact nuclear membrane for successful transposition and replication. For retrotransposition to occur, at least a subset of Ty1 proteins, including the Ty1 integrase, must enter the nucleus. Nuclear localization of integrase is dependent upon a C-terminal nuclear targeting sequence. However, the nuclear import machinery that recognizes this nuclear targeting signal has not been defined. We investigated the mechanism by which Ty1 integrase gains access to nuclear DNA as a model for how other retroelements, including retroviruses like HIV, may utilize cellular nuclear transport machinery to import their essential nuclear proteins. We show that Ty1 retrotransposition is significantly impaired in yeast mutants that alter the classical nuclear protein import pathway, including the Ran-GTPase, and the dimeric import receptor, importin-α/β. Although Ty1 proteins are made and processed in these mutant cells, our studies reveal that an integrase reporter is not properly targeted to the nucleus in cells carrying mutations in the classical nuclear import machinery. Furthermore, we demonstrate that integrase coimmunoprecipitates with the importin-α transport receptor and directly binds to importin-α. Taken together, these data suggest Ty1 integrase can employ the classical nuclear protein transport machinery to enter the nucleus

Long-term multiwavelength monitoring and reverberation mapping of NGC 2617 during a changing-look event

We present the results of photometric and spectroscopic monitoring campaigns of the changing look AGN NGC~2617 carried out from 2016 until 2022 and covering the wavelength range from the X-ray to the near-IR. The facilities included the telescopes of the SAI MSU, MASTER Global Robotic Net, the 2.3-m WIRO telescope, Swift, and others. We found significant variability at all wavelengths and, specifically, in the intensities and profiles of the broad Balmer lines. We measured time delays of ~ 6 days (~ 8 days) in the responses of the H-beta (H-alpha) line to continuum variations. We found the X-ray variations to correlate well with the UV and optical (with a small time delay of a few days for longer wavelengths). The K-band lagged the B band by 14 +- 4 days during the last 3 seasons, which is significantly shorter than the delays reported previously by the 2016 and 2017--2019 campaigns. Near-IR variability arises from two different emission regions: the outer part of the accretion disc and a more distant dust component. The HK-band variability is governed primarily by dust. The Balmer decrement of the broad-line components is inversely correlated with the UV flux. The change of the object's type, from Sy1 to Sy1.8, was recorded over a period of ~ 8 years. We interpret these changes as a combination of two factors: changes in the accretion rate and dust recovery along the line of sight.Comment: 14 pages, 15 figures, accepted by the MNRA

The nuclear imperialism-necropolitics nexus: contextualizing Chinese-Uyghur oppression in our nuclear age

This paper provides a review of the People’s Republic of China’s (PRC) nuclear warfare and uranium mining programs in the Xinjiang Uyghur Autonomous Region. Its scope spans from the PRC’s first nuclear weapon test in Lop Nor, to contemporary issues surrounding in-situ leach uranium mining in the Yili basin, which now provides a third of PRC’s uranium. By exploring these scenarios, a lens can be placed on the parameters and limitations to Uyghur life within a nuclear state. This paper draws on the work of Achille Mbembe’s necropolitics, whereby power is persistently exercised as violence, to consider the entangled aftermath of nuclear imperialism and its effects to Uyghur bodies, environment and culture. While racialized nuclear imperialism presented Uyghur lives as inconsequential to progress in Xinjiang, post-Cold War necropolitics presents Uyghur culture as a direct threat to the progress and values of the PRC sovereign state. This paper proposes that the ongoing exploitation of nuclear Xinjiang provides an additional motivation for state-imposed necropolitical sanctions upon Uyghur people. This paper also presents anew theoretical contribution, the “nuclear imperialism-necropolitics nexus”, which offers away to consider the entangled legacies of spaces of nuclear activity, from nuclear imperialism to the post-Cold War world

HIV-1 pol Diversity among Female Bar and Hotel Workers in Northern Tanzania

A national ART program was launched in Tanzania in October 2004. Due to the existence of multiple HIV-1 subtypes and recombinant viruses co-circulating in Tanzania, it is important to monitor rates of drug resistance. The present study determined the prevalence of HIV-1 drug resistance mutations among ART-naive female bar and hotel workers, a high-risk population for HIV-1 infection in Moshi, Tanzania. A partial HIV-1 pol gene was analyzed by single-genome amplification and sequencing in 45 subjects (622 pol sequences total; median number of sequences per subject, 13; IQR 5–20) in samples collected in 2005. The prevalence of HIV-1 subtypes A1, C, and D, and inter-subtype recombinant viruses, was 36%, 29%, 9% and 27%, respectively. Thirteen different recombination patterns included D/A1/D, C/A1, A1/C/A1, A1/U/A1, C/U/A1, C/A1, U/D/U, D/A1/D, A1/C, A1/C, A2/C/A2, CRF10_CD/C/CRF10_CD and CRF35_AD/A1/CRF35_AD. CRF35_AD was identified in Tanzania for the first time. All recombinant viruses in this study were unique, suggesting ongoing recombination processes among circulating HIV-1 variants. The prevalence of multiple infections in this population was 16% (n = 7). Primary HIV-1 drug resistance mutations to RT inhibitors were identified in three (7%) subjects (K65R plus Y181C; N60D; and V106M). In some subjects, polymorphisms were observed at the RT positions 41, 69, 75, 98, 101, 179, 190, and 215. Secondary mutations associated with NNRTIs were observed at the RT positions 90 (7%) and 138 (6%). In the protease gene, three subjects (7%) had M46I/L mutations. All subjects in this study had HIV-1 subtype-specific natural polymorphisms at positions 36, 69, 89 and 93 that are associated with drug resistance in HIV-1 subtype B. These results suggested that HIV-1 drug resistance mutations and natural polymorphisms existed in this population before the initiation of the national ART program. With increasing use of ARV, these results highlight the importance of drug resistance monitoring in Tanzania

Pushing Einstein's Principles to the Extreme

this paper I will be chiefly concerned with fundamental physics. The "things" which will be named and examined will be electro-magnetic fields and Yang Mills fields, space (in the sense of space-like hyper-surface of space time), matter (Dirac fields). To explain the naming step, it is necessary to distinguish between two different types of physical laws in the traditional formulation. First, there are laws which constrain the state of a part of the world at one time. Gauss' law in electrodynamics is a most important example of such a law. In a canonical formalism these laws are called constraints. All the fundamental physical theories, including general relativity, are gauge theories, and they all obey nontrivial constraints. There are further properties which can be read off the state at one time, and which are preserved in time. I will count them among the constraints. It will be seen that our a priori structural assumptions, as poor as they are, provide for a gauge group (or a substitute for it) which can be read off the initial state, and for a notion of gauge invariants which determines what could be observable in a particular kind of system. The named things in the above list will be systems which are distinguished by the validity of constraints which are characteristic for them. The statement of the constraints must be meaningful, given only the a priori structure which is furnished by the axiomatic properties of a system. One may ask the philosophical question whether the constraints are really physical laws, or just denominations. This brings us back to the discussion above. The principle of emergence may single out some of the possible constraints as physical laws because such properties of systems are the only ones which can be observed at a macroscopic leve..