Disclosed is a resin including a structural unit represented by formula (I) and a structural unit represented by formula (a2-A), and a resist composition: ##STR00001## wherein R.sup.1 represents a hydrogen atom or a methyl group; L.sup.1 and L.sup.2 each represent —O— or —S—; s1 represents an integer of 1 to 3; s2 represents an integer of 0 to 3; R.sup.a50 represents a hydrogen atom, a halogen atom, or an alkyl group which may have a halogen atom; R.sup.a51 represents a halogen atom, a hydroxy group, an alkyl group, an alkoxy group, an alkylcarbonyl group or the like; A.sup.a50 represents a single bond or *—X.sup.a51-(A.sup.a52-X.sup.a52).sub.nb—; A.sup.a52 represents an alkanediyl group; X.sup.a51 and X.sup.a52 each represent —O—, —CO—O— or —O—CO—; nb represents 0 or 1; and mb represents an integer of 0 to 4.

An epoxy compound of formula (1) is provided. A resist composition comprising the epoxy compound is capable of adequately controlling the diffusion length of acid generated from an acid generator without sacrificing sensitivity. ##STR00001##

Provided are: a sludge dehydrating agent which can exert a steady dehydrating effect on various types of sludge and has excellent dehydration performance; and a sludge dehydration method using the sludge dehydrating agent. The sludge dehydrating agent of the present invention with a polymer which has a constituent unit derived from a cationic monomer, wherein a value k determined from an intrinsic viscosity [η] 1 [dL/g] of a 1-mol/L aqueous sodium nitrate solution of the polymer at 30° C. and an intrinsic viscosity [η] 0.01 [dL/g] of a 0.01-mol/L aqueous sodium nitrate solution of the polymer at 30° C. in accordance with formula (I) is 0.8 to 2.2 exclusive.

k=([η]0.01−[η]1)/9   (I)

A stack of ion exchange membranes suitable for water purification comprising a plurality of anion exchange membranes (AEMs) and a plurality of cation exchange membranes (CEMs), wherein the colour properties of the AEMs are visibly different to the colour properties of the CEMs. The invention also provides a process for making membrane stacks in which the likelihood of there being two consecutive membranes of like charge is reduced. Furthermore, it is easy to identify whether there are two consecutive membranes of like charge present in the stacks.

A stack of ion exchange membranes suitable for water purification comprising a plurality of anion exchange membranes (AEMs) and a plurality of cation exchange membranes (CEMs), wherein the colour properties of the AEMs are visibly different to the colour properties of the CEMs. The invention also provides a process for making membrane stacks in which the likelihood of there being two consecutive membranes of like charge is reduced. Furthermore, it is easy to identify whether there are two consecutive membranes of like charge present in the stacks.

Bipolar membranes (BPMs) comprising a cation exchange layer (CEL) and an anion exchange layer (AEL) wherein the colour properties of the CEL are visibly different to the colour properties of the AEL. The CEL and the AEL are easily distinguishable so that a stack of membranes comprising the BPMs can be built fast and without mistakes in layer order.

Bipolar membranes (BPMs) comprising a cation exchange layer (CEL) and an anion exchange layer (AEL) wherein the colour properties of the CEL are visibly different to the colour properties of the AEL. The CEL and the AEL are easily distinguishable so that a stack of membranes comprising the BPMs can be built fast and without mistakes in layer order.

A holographic recording medium composition comprising component (e): a compound having an isocyanate group or an isocyanate-reactive functional group and further having a nitroxyl radical group, wherein component (e) contains component (e-1) below: component (e-1): a compound having a heterobicyclic ring structure or a heterotricyclic ring structure, the heterobicyclic ring structure or the heterotricyclic ring structure being obtained by replacing a carbon atom in a bicyclic ring structure or a tricyclic ring structure by the nitroxyl radical group.

A holographic recording medium composition comprising component (e): a compound having an isocyanate group or an isocyanate-reactive functional group and further having a nitroxyl radical group, wherein component (e) contains component (e-1) below: component (e-1): a compound having a heterobicyclic ring structure or a heterotricyclic ring structure, the heterobicyclic ring structure or the heterotricyclic ring structure being obtained by replacing a carbon atom in a bicyclic ring structure or a tricyclic ring structure by the nitroxyl radical group.

Monomers and polymers are provided that comprise a carbon alicyclic group or heteroalicyclic group that comprises 1) one or more acid-labile ring substituents and 2) one or more ether or thioether ring substituents. Photoresists that comprise such polymers also are provided.