Provided is a method for producing a glass substrate that can reduce the dimensional change during heat treatment while avoiding shortening of facilities' service lives. A method for producing a glass substrate includes melting and forming a glass raw material to produce a glass substrate having a strain point of 690 to 750° C., wherein an average cooling rate in a temperature range from (an annealing point plus 150° C.) to (the annealing point minus 200° C.) in a cooling process during the forming is adjusted to 100 to 400° C./min to obtain the glass substrate having a degree of thermal contraction of 15 ppm or less when subjected to a heat treatment at 500° C. for an hour.

An optical fiber includes a glass portion, a primary coating layer, and a secondary coating layer. In the optical fiber, a value of microbend loss characteristic factor F.sub.μBL_GO is 2.6 ([GPa.sup.−1.Math.μm.sup.−10.5.Math.dB/turn].Math.10.sup.−27) or less, when represented by
F.sub.μBL_GO=F.sub.μBL_G×F.sub.μBL_O
by using geometry microbend loss characteristic F.sub.μBL_G and optical microbend loss characteristic F.sub.μBL_O.

A tubular member for an exhaust gas treatment device according to at least one embodiment of the present invention includes: a tubular main body made of a metal; and an insulating layer formed at least on an inner peripheral surface of the tubular main body. The insulating layer contains glass containing a crystalline substance, and the glass contains silicon, boron, and magnesium.

An optical glass includes, in terms of mol % of cations, a total amount of La.sup.3+, Y.sup.3+, and Gd.sup.3+ components falling within a range of from 5% to 65% and a total amount of Zr.sup.4+, Hf.sup.4+, and Ta.sup.5+ components falling within a range of from 5% to 65%, and a relationship expressed in Expression (1) given below is satisfied. (La.sup.3++Y.sup.3++Gd.sup.3+)×(Zr.sup.4++Hf.sup.4++Ta.sup.5+)≥400 (%).sup.2

Laser waveguides, methods and systems for forming a laser waveguide are provided. The waveguide includes an inner cladding layer surrounding a central axis and a glass core surrounding and located outside of the inner cladding layer. The glass core includes a laser-active material. The waveguide includes an outer cladding layer surrounding and located outside of the glass core. The inner cladding, outer cladding and/or core may surround a hollow central channel or bore and may be annular in shape.

Provided is a glass composition comprising a glass frit containing P.sub.2O.sub.5, BaO, ZnO, group I-based oxide and group II-based oxide, wherein the P.sub.2O.sub.5 is contained in an amount of 20 wt % to 55 wt % based on a total weight of the glass frit, wherein each of the BaO and ZnO is contained in an amount of 2 to 30% by weight based on the total weight of the glass frit, wherein the group I-based oxide is contained in an amount of 5 to 20% by weight based on the total weight of the glass frit, wherein the group II-based oxide is contained in an amount of 1 to 15% by weight based on the total weight of the glass frit.

A manufacturing method for an optical fiber, includes: drawing, while heating in a heating furnace, a lower end of an optical fiber preform that is to be an optical fiber having a core consisting of silica glass containing a rare earth element compound. The heating furnace has a temperature profile in which a temperature of the heating furnace increases to a maximum temperature T.sub.max and then decreases from an upstream side of the heating furnace toward a downstream side of the heating furnace. The temperature profile has a changing point at which the temperature decreases more steeply on the downstream side from a position where the maximum temperature T.sub.max is reached. At the maximum temperature, a temperature of the silica glass is higher than or equal to a glass transition temperature and the silica glass is in a single phase.

Annealing treatments for modified titania-silica glasses and the glasses produced by the annealing treatments. The annealing treatments include an isothermal hold that facilitates equalization of non-uniformities in fictive temperature caused by non-uniformities in modifier concentration in the glasses. The annealing treatments may also include heating the glass to a higher temperature following the isothermal hold and holding the glass at that temperature for several hours. Glasses produced by the annealing treatments exhibit high spatial uniformity of CTE, CTE slope, and fictive temperature, including in the presence of a spatially non-uniform concentration of modifier.

To provide a glass composition which can be used for a dental porcelain or a dental ceramics coloring material, and has low temperature meltability, acid resistance and preservation stability under the humid environment which are required for a dental porcelain or a dental ceramics coloring material, and a dental porcelain and dental ceramics coloring material which contain the glass composition of the present disclosure. To provide a low melting glass composition with softening point (Ts) less than 600° C. comprising as a component; SiO.sub.2: 55.0 to 75.0 wt. %, B.sub.2O.sub.3: 6.1 to 12.0 wt. %, Al.sub.2O.sub.3: 2.0 to 8.0 wt. %, ZnO: 2.0 to 8.5 wt. % and two or more kinds of alkali metal oxide: 10.5 to 20.0 wt. %.

An article includes SiO.sub.2 from about 40 mol % to about 80 mol %, Al.sub.2O.sub.3 from about 1 mol % to about 20 mol %, B.sub.2O.sub.3 from about 3 mol % to about 50 mol %, WO.sub.3 plus MoO.sub.3 from about 1 mol % to about 18 mol % and at least one of: (i) Au from about 0.001 mol % to about 0.5 mol %, (ii) Ag from about 0.025 mol % to about 1.5 mol %, and (iii) Cu from about 0.03 mol % to about 1 mol %, and R.sub.2O from about 0 mol % to about 15 mol %. The R.sub.2O is one or more of Li.sub.2O, Na.sub.2O, K.sub.2O, Rb.sub.2O and Cs.sub.2O. R.sub.2O minus Al.sub.2O.sub.3 ranges from about 12 mol % to about 3.8 mol %.