다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

▪ Abstract Breathing is a vital behavior that is particularly amenable to experimental investigation. We review recent progress on three problems of broad interest. (i) Where and how is respiratory rhythm generated? The preBotzinger Complex is a critical site, whereas pacemaker neurons may not be essential. The possibility that coupled oscillators are involved is considered. (ii) What are the mechanisms that underlie the plasticity necessary for adaptive changes in breathing? Serotonin-dependent long-term facilitation following intermittent hypoxia is an important example of such plasticity, and a model that can account for this adaptive behavior is discussed. (iii) Where and how are the regulated variables CO2 and pH sensed? These sensors are essential if breathing is to be appropriate for metabolism. Neurons with appropriate chemosensitivity are spread throughout the brainstem; their individual properties and collective role are just beginning to be understood.

Breathing: Rhythmicity, plasticity, chemosensitivity

Metallic and ceramic surfaces can be rendered hydrophobic through a combination of multiscale surface structures and polymeric modifiers, but the imparted hydrophobicity is not robust to harsh environments. It is now shown that the lanthanide oxide series—a class of ceramics—is intrinsically hydrophobic as a result of their unique electronic structure, even after exposure to high temperatures and abrasive wear.

Hydrophobicity of rare-earth oxide ceramics

THE difficulty of reconciling line spectra with the kinetic theory of gases, has been referred to by Prof. Fitzgerald (NATURE, January 3, p. 221). The following considerations show that it is possible under certain suppositions to have a number of spectral rays with a very restricted number of degrees of freedom. Most of us, I believe, now accept a definite atomic charge of electricity, and if each charge is imagined to be capable of moving along the surface of an atom, it would represent two degrees of freedom. If a molecule is capable of sending out a homogeneous vibration, it means that there must be a definite position of equilibrium of the “electron.” If there are several such positions, the vibrations may take place in several periods. Any one molecule may perform for a certain time a simple periodic oscillation about one position of equilibrium, and owing to some impact the electron may be knocked over into a new position. The vibrations under these circumstances would not be quite homogeneous, but if the electron oscillates about any one position sufficiently long to perform a few thousand oscillations, we should hardly notice the want of homogeneity. Each electron at a given time would only send out vibrations which in our instruments would appear as homogeneous. Each molecule could thus successively give rise to a number of spectral rays, and at any one time the electron in the different molecules would, by the laws of probability, be distributed over all possible positions of equilibrium, so that we should always see all the vibrations which any one molecule of the gas is capable of sending out. The probability of an electron oscillating about one of its positions of equilibrium need not be the same in all cases. Hence a line may be weak not because the vibration has a smaller amplitude, but because fewer molecules give rise to it. The fact that the vibrations of a gas are not quite homogeneous, is borne out by experiment. If impacts become more frequent by increased pressure, we should expect from the above views that the time during which an electron performs a certain oscillation is shortened; hence the line should widen, which is the case. I have spoken, for the sake of simplicity, as if an electron vibrating about one position of equilibrium could only do so in one period. If the forces called into play, by a displacement, depend on the direction of the displacement, there would be two possible frequencies. If the surface is nearly symmetrical, we should have double lines.

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The Kinetic Theory of Gases

Stainless steel, Co-Cr and Ni-Cr alloys have played an important role in many industrial sectors to combat environmental degradation. However, low hardness and poor wear properties have impeded their tribological and tribochemical applications. Conventional thermochemical treatments can be used to significantly harden these passive alloys but at the expense of their corrosion resistance due to precipitation induced depletion of Cr in the matrix. Research in 1980s led to the discovery of a new expanded austenite phase, i.e. so called S-phase with combined improvement in wear and corrosion resistance. Recent research has revealed that S-phase can be formed not only in stainless steels but also in Co-Cr alloys and Ni-Cr alloys. It is the purpose of this paper to critically review the S-phase surface engineering of stainless steels, Co-Cr alloys and Ni-Cr alloys. Particular attention will be paid to the structure, formation conditions, supersaturation, hardening mechanisms and metastability of...

S-phase surface engineering of Fe-Cr, Co-Cr and Ni-Cr alloys

Cathodic electrodeposition of cerium-based oxides on carbon steel from concentrated cerium nitrate solutions: Part I. Electrochemical and analytical characterisation

pH-distribution of cerium species in aqueous systems

Surface study of cerium oxide based coatings obtained by cathodic electrodeposition on zinc

Characterization and oxidation resistance of additive manufactured and forged IN718 Ni-based superalloys

The deposition of Al and Cr on steel coupons by chemical vapor deposition in fluidized bed reactors (CVD-FBR) has been studied. Before performing the experiments, thermochemical calculations were run using the free-energy minimization method afforded by the HSC Chemistry software. Metal sub-halide chemistry was used to produce the gas precursors of deposition. With this method we have achieved 10 μm thick Al coatings at low deposition temperatures and short deposition times. However, we have not yet succeeded in the deposition of Cr and further work is needed.

Fernando Pedraza

Papers

Cathodic electrodeposition of cerium-based oxides on carbon steel from concentrated cerium nitrate solutions: Part I. Electrochemical and analytical characterisation

pH-distribution of cerium species in aqueous systems

Surface study of cerium oxide based coatings obtained by cathodic electrodeposition on zinc

Characterization and oxidation resistance of additive manufactured and forged IN718 Ni-based superalloys

Aluminizing and chromizing bed treatment by CVD in a fluidized bed reactor on austenitic stainless steels