754 research outputs found
End of the World Branes from Dimensional Reduction
We consider dimensional reduction of cigar geometries which are obtained by a
Wick rotation of black hole solutions. Originally the cigar geometry is smooth
around the tip, but after the dimensional reduction along the Euclidean time
direction, there appears an end-of-the-world brane (ETW brane). We derive the
tension of the brane by two methods: bulk equations of motion and boundary
equations of motion. In particular, for AdS7-soliton cross S4 and AdS4-soliton
cross S7 backgrounds in M-theory, we find that the tension of the emerging ETW
branes behaves as exp(-3Phi) in the string frame. This indicates the existence
of such ETW branes in the strongly coupled regime of type 0A string theory.Comment: 21 pages, 1 figure. Reference added for v
Methods to induce perpendicular magnetic anisotropy in full-Heusler Co2FeSi thin layers in a magnetic tunnel junction structure
In this study, to obtain perpendicular magnetic tunnel junctions (p-MTJs)
using half-metallic ferromagnets (HMFs), several methods were developed to
induce perpendicular magnetic anisotropy (PMA) in full-Heusler Co2FeSi (CFS)
alloy thin layers in an MTJ multilayer composed of a layered CFS/MgO/CFS
structure. Oxygen exposure at 2.0 Pa for 10 min after deposition of the bottom
CFS layer was effective for obtaining PMA in the CFS layer. One of the reasons
for the PMA is the formation of nearly ideal CFS/MgO interfaces due to oxygen
exposure before the deposition of the MgO layer. The annealing process was
effective for obtaining PMA in the top CFS layer capped with a Pd layer. PMA
was clearly observed in the top CFS layer of a Cr(40 nm)/Pd(50 nm)/bottom
CFS(0.6 nm)/MgO(2.0 nm)/top CFS(0.6 nm)/Pd(10 nm) multilayer, where the top CFS
and Pd thin films were deposited at RT and subsequently annealed at 300{\deg}C.
In addition to the continuous layer growth of the films, the crystalline
orientation alignment at the top CFS/Pd interface probably attributes to the
origin of PMA at the top CFS layer.Comment: 16 pages, 4 figure
Bubbly Flows through a Convergent-Divergent Nozzle
Characteristics of bubbly flow with a small void fraction through a vertical, two-dimensional, converging-diverging nozzle are investigated experimentally and numerically. Emphasis is placed on the mechanism for large velocity slip near the nozzle throat, where the pressure gradient is very large. Bubble velocities are measured by taking double-exposure photographs with stroboscopic light sources having a flash duration of a few μ sec. The pressure distribution of the mixture along the nozzle axis is measured by semiconductor pressure transducers. The local liquid velocity is determined through continuity equations of gas and liquid in conjunction with the measured data of pressure distribution and experimental conditions at the nozzle inlet and exit. The power spectrum density of the pressure fluctuations is measured to investigate some instabilty of the bubbly flow, which is believed to be inherent to the velocity slip. It is proved that the numerical results using Wijngaarden's model equations agree well with the experiments. The characteristics of flow instability are explained according to the theoretical predictions of Morioka et al
Formation of Polyurethane Film Containing Silicone Polymer with Silanol Residue
The silicone polymers containing a silanol residue were synthesized from silica gel, while the polyurethanes (PUs) bearing a carboxyl moiety were prepared using 2,2-bis(hydroxymethyl)propionic acid (BHMPA) as one of the diol components. The fabrication of the PU films was carried out using these two polymers, then the tensile and thermal properties were investigated. Both the amounts of the carboxyl side groups of the PU chain and the residual silanol of the silicone polymer significantly affected the mechanical property of the film, in addition, the incorporation of 3-aminopropyltrimethoxysilane (APTMS) was quite effective for enhancing the elastic modulus (E). As a result, the film prepared from the polyurethane containing the BHMPA unit with a combination of APTMS and the silicone polymer, having a proper amount of silanol groups, showed the highest effect (E = 5.36 N/mm2), while that observed for the film prepared without using BHMPA and a silicone polymer was 2.10 N/mm2. An acid-base interaction between the carboxyl moiety of the PU and amino group of APTMS occurred, while the formation of the siloxane linkage through the silylation reaction between the trimethoxysilyl group of APTMS and silanol also took place
Discriminating DRDoS Packets using Time Interval Analysis
Distributed Reflection Denial of Service (DRDoS) attack is one of the critical security threats. As the attack generates unidirectional traffic, it is not easy for the targets of the attack to protect themselves. To mitigate the attack, we need a defense mechanism installed at backbone networks, i.e., detecting and blocking the attack traffic before they reach to the destinations. A conventional approach is to monitor the traffic volume of the attack, i.e., an attack is detected if the observed traffic volume exceeds a certain threshold. However, such a simple approach may not work when an attacker adjusts the traffic volume to evade the detection. This paper proposes a novel method that can detect the DRDoS attacks accurately. The key idea is to leverage the characteristics of time intervals between the packets. We make use of the K-means clustering algorithm to find the best threshold values used to distinguish packets associated with DRDoS attacks. We implement the proposed algorithm into an equipment at a data center and demonstrate that our approach attains high accuracy
Thin anterior uterine wall with incomplete uterine rupture in a primigravida detected by palpation and ultrasound: a case report
<p>Abstract</p> <p>Introduction</p> <p>Uterine rupture is an obstetric complication associated with significant maternal and fetal morbidity and mortality. This disorder usually occurs with a scarred uterus, especially in a uterus with prior Cesarean section. Uterine sacculation or diverticulum may also lead to a thin uterine wall during pregnancy.</p> <p>Case presentation</p> <p>A 27-year-old Japanese primigravid woman was admitted to our hospital due to weak, irregular uterine contractions in her 38<sup>th </sup>week of gestation. She had no past history of uterine surgery or known diseases. A hard mass was palpable in her abdomen. An ultrasound revealed that the anterior uterine wall was thin and bulging, with a fetal minor part beneath it which corresponded to the palpated mass. A Cesarean section was performed which revealed a thin anterior uterine wall with incomplete uterine rupture. The woman and baby were healthy.</p> <p>Conclusions</p> <p>Although extremely rare, an unscarred primigravid uterus can undergo incomplete rupture even without discernable risk factors or labor pains. Abdominal palpation and ultrasound may be useful in detecting this condition.</p
コウヒンシツ コロイド ケッショウ セイチョウ ギジュツ ノ カクリツ
To grow large and high-quality colloidal crystals, several techniques have been investigated. Apparatus for soap-free emulsion polymerization was built up. Synthesis of surfactant-free polystyrene microparticles colloidal dispersions with small diameter dispersion was achieved. Reduction of particle size polydispersity by crystallization, preceded by a thermodynamic consideration, was attempted and worked in few conditions. In-situ observation was found to be a fruitful method to obtain the information of crystallization process
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