4,836 research outputs found
Quantum-Mechanical Detection of Non-Newtonian Gravity
In this work the possibility of detecting the presence of a Yukawa term, as
an additional contribution to the usual Newtonian gravitational potential, is
introduced. The central idea is to analyze the effects at quantum level
employing interference patterns (at this respect the present proposal resembles
the Colella, Overhauser and Werner experiment), and deduce from it the possible
effects that this Yukawa term could have. We will prove that the corresponding
interference pattern depends on the phenomenological parameters that define
this kind of terms. Afterwards, using the so called restricted path integral
formalism, the case of a particle whose position is being continuously
monitored, is analyzed, and the effects that this Yukawa potential could have
on the measurement outputs are obtained. This allows us to obtain another
scheme that could lead to the detection of these terms. This last part also
renders new theoretical predictions that could enable us to confront the
restricted path integral formalism against some future experiments.Comment: 17 pages, accepted in International Journal of Modern Physics
Molecular Tools for Focused Proteomic Analysis of Bacterial Cell Factories
Cell factories are important and new tools to produce valuable products without depending on depleting fossil fuels. As there are successive cell factory constructions, there are emerging needs to develop better analysis tools for them. The conventional analysis methods such as 2-dimentional electrophoresis and mass spectrometry are certainly eligible for cell factory analysis, but they are not necessarily the most reasonable methods because of the need for special equipment. Therefore, new tools for cell factory analysis are needed.
Aldehyde-deformylating oxygenase (ADO) and bacterial luciferase (LuxAB) are interesting target proteins whose bacterial productions were analyzed here: ADO is an enzyme involved in fatty alkanes or alkenes generation in bacteria, and LuxAB is an enzyme catalyzing the bioluminescence production. Fatty alkanes and alkenes production by bacteria is drawing attention since it could replace the traditional chemical production of traffic fuels. Bioluminescence is also notable because it can be used as a real-time monitoring tool for certain bacterial production.
Therefore, in this study, immunoassay was studied as a new method for cell factory analysis. Especially, the immunoassay systems for ADO and LuxAB were constructed. The best working scFvs for the immunoassays were successfully selected, and the standard curves were also drawn for both of them. Thus, enzyme immunoassay using alkaline phosphatase (phoA) for ADO and a new immunoassay for LuxAB were established in this study. In the immunoassay for LuxAB, LuxAB generates the signals to be measured using exogenously added long-chain aldehyde as substrate, thus no tracer scFv or labels are needed. The systems were confirmed to work with ADO and LuxAB produced by Escherichia coli but not by Acinetobacter baylyi ADP1. The possible reason could be that A. baylyi ADP1 strains did not produce enough amounts of the proteins for the immunoassays. Thus, further research is still needed, but this study offers a meaningful foundation for the development of the immunoassays
Sequential Development of Putaminal Hemorrhage and Corona Radiata Infarction in the Same Lenticulostriate Arterial Territory
Putaminal hemorrhage is a common type of spontaneous cerebral hemorrhage. However, to our knowledge, there have been no reports of sequential cerebral hemorrhage and infarction in the same perforating arterial territory. Herein, we present the first reported case of the sequential development of putaminal hemorrhage and corona radiata infarction in the same lenticulostriate arterial (LSA) territory. Early intensive blood pressure lowering treatment may have aggravated ischemic damage. If a patient presents with motor weakness that cannot be explained by putaminal hemorrhage, the sequential development of corona radiata infarction in the same LSA territory should be ruled out
Dynamical constraints on the origin of the young B-stars in the Galactic center
Regular star formation is thought to be inhibited close to the massive black
hole (MBH) in the Galactic center. Nevertheless, tens of young main sequence B
stars have been observed in an isotropic distribution close to it. Various
models have been suggested for the formation of the B-stars closest to the MBH
(<0.05 pc; the S-stars), typically involving the migration of these stars from
their original birthplace to their currently observed position. Here we explore
the orbital phase space distribution of the B-stars throughout the central pc
expected from the various suggested models for the origin of the B-stars. We
find that most of these models have difficulties in explaining, by themselves,
both the population of the S-stars (<0.05 pc), and the population of the young
B-stars further away (up to 0.5 pc). Most models grossly over-predict the
number of B-stars up to 0.5 pc, given the observed number of S-stars. Such
models include the intermediate-mass black hole assisted cluster inspiral
scenario, Kozai-like perturbations by two disks, spiral density waves migration
in a gaseous disk, and some of the eccentric disk instability models. We focus
on one of the other models, the massive perturber induced binary disruption,
which is consistent with both the S-stars and the extended population of
B-stars further away. For this model we use analytical arguments and N-body
simulations to provide further observational predictions. These could be
compared with future observations to further support this model, constrain it
or refute it. These predictions include the radial distribution of the young
B-stars, their eccentricity distribution and its dependence on distance from
the MBH (higher eccentricities at larger distances from the MBH), as well as
less specific expectations regarding their mass function.Comment: Comments are welcome
Fabrication and optical properties of nano-structured semipolar InGaN/GaN quantum wells on c-plane GaN template
High density self-assembled nanostructured semipolar (NSSP) GaN pyramids are fabricated based on c-plane GaN template by in situ silane treatment followed by high temperature treatment. Semipolar InGaN/GaN multiple quantum wells (MQWs) were subsequently grown on the NSSP GaN. Optical properties of the MQWs were studied by temperature- dependent and excitation density varied photoluminescence. It was found that the internal electric field in the NSSP MQWs were remarkably reduced in comparison with planar c-plane MQWs. The internal quantum efficiency of the NSSP MQWs was measured to be > 30% which showed potential applications in III-nitride light emitters. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58655/1/1618_ftp.pd
Time-resolved photoluminescence studies of the energy transfer from excitons confined in Si nanocrystals to oxygen molecules
Perturbations of Intermediate-mass Black Holes on Stellar Orbits in the Galactic Center
We study the short- and long-term effects of an intermediate mass black hole
(IMBH) on the orbits of stars bound to the supermassive black hole (SMBH) at
the center of the Milky Way. A regularized N-body code including post-Newtonian
terms is used to carry out direct integrations of 19 stars in the S-star
cluster for 10 Myr. The mass of the IMBH is assigned one of four values from
400 Msun to 4000 Msun, and its initial semi-major axis with respect to the SMBH
is varied from 0.3-30 mpc, bracketing the radii at which inspiral of the IMBH
is expected to stall. We consider two values for the eccentricity of the
IMBH/SMBH binary, e=(0,0.7), and 12 values for the orientation of the binary's
plane. Changes at the level of 1% in the orbital elements of the S-stars could
occur in just a few years if the IMBH is sufficiently massive. On time scales
of 1 Myr or longer, the IMBH efficiently randomizes the eccentricities and
orbital inclinations of the S-stars. Kozai oscillations are observed when the
IMBH lies well outside the orbits of the stars. Perturbations from the IMBH can
eject stars from the cluster, producing hypervelocity stars, and can also
scatter stars into the SMBH; stars with high initial eccentricities are most
likely to be affected in both cases. The distribution of S-star orbital
elements is significantly altered from its currently-observed form by IMBHs
with masses greater than 1000 Msun if the IMBH/SMBH semi-major axis lies in the
range 3-10 mpc. We use these results to further constrain the allowed
parameters of an IMBH/SMBH binary at the Galactic center.Comment: 11 pages, 13 figures, revised versio
Theory of nonlinear optical properties of phenyl-substituted polyacetylenes
In this paper we present a theoretical study of the third-order nonlinear
optical properties of poly(diphenyl)polyacetylene (PDPA) pertaining to the
third-harmonic-generation (THG) process. We study the aforesaid process in
PDPA's using both the independent electron Hueckel model, as well as
correlated-electron Pariser-Parr-Pople (P-P-P) model. The P-P-P model based
calculations were performed using various configuration interaction (CI)
methods such as the the multi-reference-singles-doubles CI (MRSDCI), and the
quadruples-CI (QCI) methods, and the both longitudinal and the transverse
components of third-order susceptibilities were computed. The Hueckel model
calculations were performed on oligo-PDPA's containing up to fifty repeat
units, while correlated calculations were performed for oligomers containing up
to ten unit cells. At all levels of theory, the material exhibits highly
anisotropic nonlinear optical response, in keeping with its structural
anisotropy. We argue that the aforesaid anisotropy can be divided over two
natural energy scales: (a) the low-energy response is predominantly
longitudinal and is qualitatively similar to that of polyenes, while (b) the
high-energy response is mainly transverse, and is qualitatively similar to that
of trans-stilbene.Comment: 13 pages, 7 figures (included), to appear in Physical Review B (April
15, 2004
Onset Temperatures for Superconducting Fluctuations in Te-annealed FeTeSe Single Crystals: Evidence for the BCS-BEC Crossover
Recently, the superconductors' community has witnessed an unsettled debate
regarding whether iron-based superconductors, in particular FeSe and
FeSeS, are in the Bardeen-Cooper-Shrieffer (BCS) - Bose-Einstein
condensation (BEC) crossover regime. Nonetheless, one particular system,
FeTeSe, has been less investigated in this regard owing to the
screening of its intrinsic superconducting properties by the inevitable iron
excess. Herein, the onset temperatures for superconducting fluctuations
() are investigated by measuring the magnetoresistance (MR) of
Te-annealed, high-quality FeTeSe ( = 0.1, 0.2, 0.3, and 0.4)
single crystals. The results reveal very high values for these
crystals. Particularly for = 0.4, reaches approximately 40 K,
which is 2.7 times larger than . This indicates that the superconductivity
of the FeTeSe system is well within the BCS-BEC crossover regime.Comment: 6 pages, 3 figures, and 1 table. to be published in JPS Conference
Proceeding
Stargazer: Long-Term and Multiregional Measurement of Timing/ Geolocation-Based Cloaking
Malicious hosts have come to play a significant and varied role in today's cyber attacks. Some of these hosts are equipped with a technique called cloaking, which discriminates between access from potential victims and others and then returns malicious content only to potential victims. This is a serious threat because it can evade detection by security vendors and researchers and cause serious damage. As such, cloaking is being extensively investigated, especially for phishing sites. We are currently engaged in a long-term cloaking study of a broader range of threats. In the present study, we implemented Stargazer, which actively monitors malicious hosts and detects geographic and temporal cloaking, and collected 30,359,410 observations between November 2019 and February 2022 for 18,397 targets from 13 sites where our sensors are installed. Our analysis confirmed that cloaking techniques are widely abused, i.e., not only in the context of specific threats such as phishing. This includes geographic and time-based cloaking, which is difficult to detect with single-site or one-shot observations. Furthermore, we found that malicious hosts that perform cloaking include those that survive for relatively long periods of time, and those whose contents are not present in VirusTotal. This suggests that it is not easy to observe and analyze the cloaking malicious hosts with existing technologies. The results of this study have deepened our understanding of various types of cloaking, including geographic and temporal ones, and will help in the development of future cloaking detection methods
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