To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
To understand the lubrication-dominated permeation through a membrane, numerical simulations of permeation through a moving corrugated permeable membrane is carried out with a fully validated numerical method. Through comparisons between the numerical results and the results of an asymptotic analysis of permeate flux (under an infinitesimal permeability condition) using Reynolds lubrication equation, the effect of permeation on lubrication and its inverse effect (i.e., the dependence of permeation on lubrication) are discussed. The linear and non-linear dependences of the relaxation of the lubrication pressure due to membrane permeation are identified. The effect of the tangential component of the permeate flux is evaluated by a linear analysis, and the limitation of Reynolds-type lubrication is discussed.
We estimate the column density of the Galactic foreground interstellar medium (GFISM) in the direction of extragalactic sources. All-sky AKARI FIS infrared sky survey data might be used to trace the GFISM with a resolution of 2 arcminutes. The AKARI based GFISM hydrogen column density estimates are compared with similar quantities based on HI 21cm measurements of various resolution and of Planck results. High spatial resolution observations of the GFISM may be important recalculating the physical parameters of gamma-ray burst (GRB) host galaxies using the updated foreground parameters.
Early results from the SAGE-SMC (Surveying the Agents of Galaxy Evolution in the tidally-disrupted, low-metallicity Small Magellanic Cloud) Spitzer legacy program are presented. These early results concentrate on the SAGE-SMC MIPS observations of the SMC Tail region. This region is the high H i column density portion of the Magellanic Bridge adjacent to the SMC Wing. We detect infrared dust emission and measure the gas-to-dust ratio in the SMC Tail and find it similar to that of the SMC Body. In addition, we find two embedded cluster regions that are resolved into multiple sources at all MIPS wavelengths.
The formation of stellar clusters is one of the biggest issues in Astronomy. In our Galaxy, the currently formed
clusters are only open clusters; no “young” globular clusters have been observed. On the other hand, in the LMC,
stellar clusters called “populous clusters” are found to be forming at present. Comparative studies of young stars
as well as the properties of giant molecular clouds both in our Galaxy and LMC are therefore of vital importance.
We present here the statistical comparison of the distribution of YSOs with that of CO molecular clouds detected by
the NANTEN CO survey throughout the entire galaxy. The Spizter/SAGE dataset provides the most comprehensive and complete knowledge
on how and where the YSOs are distributed in the LMCs for the first time. The distribution of SAGE sources with a cold
spectrum shows good correlation with that of molecular clouds, indicating that these sources are good candidates for YSOs.
Theory predicts the triggered formation of molecular clouds stars through the fragmentation and collapse of swept-up ambient gas. Yet the majority of Galactic HI shells show no more than a scattering of small molecular clouds. The Carina Flare supershell (Fukui et al. 1999) is a rare example of an HI shell with a striking molecular component. Here we present the large-scale morphology of the molecular and atomic gas and the location of YSO candidates. A detailed look at two molecular clumps in the shell walls reveals active, intermediate mass star forming regions at various stages of early evolution.
In order to elucidate star formation in the Large Magellanic Cloud, a complete survey of the molecular clouds was carried out by NANTEN. In this work, we compare 230 giant molecular clouds (GMCs), whose physical quantities are well determined, with young clusters and Hii regions. We find that about 76% of the GMCs are actively forming stars or clusters, while 24% show no signs of massive star or cluster formation. Effects of supergiant shells (SGSs) on the formation of GMCs and stars are also studied. The number and surface mass densities of the GMCs are higher by a factor of 1.5–2 at the edge of the SGSs than elsewhere. It is also found that young stellar clusters are more actively formed in the GMCs facing to the center of the SGSs. These results are consistent with the previous studies by Yamaguchi et al. and suggest the formation of GMCs and the cluster is triggered by dynamical effects of the SGSs.
The new molecular image obtained by NANTEN telescope in the galactic center has revealed the existence of the two loop like structures, loop 1 and loop 2, which have never been seen before toward l = 355° to 358°. The velocities of loop 1 and loop 2 are −180 to −90 km s−1 and −90 and −40 km s−1, respectively, and these two loops have strong velocity gradients. The foot points of the loops show a very broad linewidth of ~40 to 80 km s−1 whose large velocity spans are characteristic of the molecular gas near the galactic center. Therefore, we classified the loops as being located in the galactic center and adopt a distance of 8.5 kpc. Then, the projected lengths of loop 1 and loop 2 were estimated as ~500 and ~300 pc, respectively and velocity gradients corresponds to ~80 km s−1 per 250 pc along loop 1 and ~60 km s−1 per 150 pc along loop 2. The heights of these loops are also estimated as ~220 to ~300 pc from the galactic plane, significantly higher than the typical scale height in the nuclear disk.
External shock triggering and internal turbulence play major role for the condensation of the ISM and star formation. Some evidences of shock triggering by non-isotropic compression are seen in the cloud morphologies and associated active cluster formation such as the ρ Oph and Cha I clouds. Surveys for C18O dense cores have shown that internal turbulence dominates the core dynamics and regulates star formation activity (Tachihara et al. 2002).
In this contribution, we will overview the NANTEN observations of molecular clouds faced to H II regions, supershells, and interacting galaxies, which demonstrate that star/molecular cloud formation is being triggered by young OB associations, supershells, and collisions between galaxies. The large volume filling factor of explosive events like supernovae, ultraviolet radiation fields and stellar winds of massive stars suggest that most of the interstellar medium has been agitated by such strong impacts and triggered star formation is a common event at all scales from small molecular clouds to large galaxy-galaxy mergers. The consequence is the increase of star formation efficiency in many cases, and that more massive stars or clusters of more member stars tend to be formed by triggering than in spontaneous star formation.
In order to simplify a fabrication process of silicon carbide power MOSFETs (metal oxide semiconductor field effect transistors), development of a simultaneous formation process of ohmic contacts to both the p-well and n-source regions of the SiC devices using same contact materials and one step annealing was challenged. We succeeded to develop NiAl-based contact materials which provided ohmic behaviors for both n- and p-type 4H-SiC after one step annealing. The Ni/Al and Ni/Ti/Al ohmic contacts were prepared by depositing sequentially Ni, (Ti) and Al layers with various layer thicknesses onto the n- and p-type SiC substrates which were doped with N at 1 × 1019 cm-3 and with Al at 8 × 1018 cm-3, respectively. The Ni(50 nm)/Al(5 ~ 6 nm) contacts showed ohmic behaviors for both the n- and p-type SiC substrates after annealing at 1000 °C. The Ni(20 nm)/Ti(50 nm)/Al(50 ~ 70 nm) contacts showed ohmic behaviors for both the n- and p-type SiC substrates after annealing at a lower temperature of 800 °C. The specific contact resistances of these contacts were measured to be in the order of 10-3 Ω-cm2 for both p- and n-type SiC, and were found to have strong dependence of the Al layer thicknesses of materials. The interfacial microstructures of the NiAl-based contacts were also observed by transmission electron microscopy (TEM) to understand the current transport mechanism through the metal/SiC interfaces.
An ion-assisted chemical vapor deposition method by which Cu is deposited preferentially from the bottom of trenches (anisotropic CVD) has been proposed in order to fill small via holes and trenches. By using Ar + H2 + C2H5OH[Cu(hfac)2] discharges with a ratio H2 / (H2 + Ar) = 83%, Cu is filled preferentially from the bottom of trenches without deposition on the sidewall and top surfaces. The deposition rate on the bottom surface of trenches is experimentally found to increase with decreasing its width.
To facilitate CMOS scaling beyond the 65 nm technology node, high-permittivity gate dielectrics such as HfO2 will be needed in order to achieve sub-1.3nm equivalent oxide thickness (EOT) with suitably low gate leakage, particularly for low-power applications. Polycrystalline silicon-germanium (poly-SiGe) is a promising gate material because it is compatible with a conventional CMOS process flow, and because it can yield significantly lower electrical gate-oxide thickness as compared with poly-Si. In this paper, the effects of the gate material (Si vs. SiGe) and gate deposition rate on EOT and gate leakage current density are investigated. Poly-Si0.75Ge0.25 gate material yields the lowest EOT and is stable up to 950°C for 30 seconds, providing 2 orders of magnitude lower leakage current compared to poly-Si gate material. A faster gate deposition rate (achieved by using S2H6 instead of SiH4 as the gaseous Si source) is also effective for minimizing the increases in EOT and leakage current with high-temperature annealing.
We have made a 12CO(J = 1−0) survey of the LMC with NANTEN. A sample of 55 giant molecular clouds has been identified and comparisons with stellar clusters, HII regions and SNRs are presented. The connection between the clouds and cluster formation is discussed.
Composites of perfluorinated polymer electrolyte membrane and gold electrodes bend in response to low-voltage electric stimuli and work as soft actuators like muscles. The composites were prepared by chemical plating. Charge on the electrode induces electric double layer and electro-osmotic drag of water by cation from anode to cathode through narrow channels in the perfluorinated ion-exchange resin. The electro-osmotic flow of water swells the polymer near the cathode rather than anode, and the membrane bends to the anode. The actuator comprises polymer electrolyte, electrodes, counter ion, solvent, lead wires, etc. Each component affects the performance of the actuator. Surface area of electrode and species of counter ion have drastic effect on voltage-displacement response. The response may depend on water channel structure of the polymer electrolyte. Modification of these factors improved the performance and resulted in the deflection over 360 degrees at a film actuator of 10 mm length. A tubular actuator was demonstrated as a multidirectional actuator. These actuators are applicable to artificial muscle, micro robots, or micro medical equipment inside body.
Fully sampled 12CO(J=1−0) observations of the whole extent of the LMC have been made with a linear resolution of ~ 30 pc at a detection limit of N(H2) = 2 × 1021 cm−2. In addition, several selected regions have been mapped with higher sensitivity corresponding to a detection limit of 1 × 1021 cm−2. Based on these results, a new estimate of the molecular mass in the LMC is presented.
We have made 12CO(J=1−0) observations of the LMC with NANTEN. We report the results of a comparison between CO clouds and SNRs in the LMC. Among the 35 known SNRs, only 10 are possibly associated with CO clouds. These 10 CO clouds and SNRs deserve follow-up studies for possible interactions. We present overlays of CO clouds on the optical images of some of these SNRs.