Chitosan: an integrative biomaterial for lab-on-a-chip devices.

Chitosan is a naturally derived polymer with applications in a variety of industrial and biomedical fields. Recently, it has emerged as a promising material for biological functionalization of microelectromechanical systems (bioMEMS). Due to its unique chemical properties and film forming ability, chitosan serves as a matrix for the assembly of biomolecules, cells, nanoparticles, and other substances. The addition of these components to bioMEMS devices enables them to perform functions such as specific biorecognition, enzymatic catalysis, and controlled drug release. The chitosan film can be integrated in the device by several methods compatible with standard microfabrication technology, including solution casting, spin casting, electrodeposition, and nanoimprinting. This article surveys the usage of chitosan in bioMEMS to date. We discuss the common methods for fabrication, modification, and characterization of chitosan films, and we review a number of demonstrated chitosan-based microdevices. We also highlight the advantages of chitosan over some other functionalization materials for micro-scale devices.

[Differential indicators of loneliness among elderly. The importance of type of partner relationship, partner history, health, socioeconomic status and social relations]. / Differentiële kansen op eenzaamheid onder ouderen. De betekenis van type partnerrelatie, partnergeschiedenis, gezondheid, sociaal-economische positie en sociale relaties.

Using data from the 1992 NESTOR-survey 'Living arrangements and social networks of older adults' (N = 4494), the aim of the present study is to identify specific categories of older adults who are most vulnerable to loneliness. By looking at different types of partner relationships (first, second, and third marriages; consensual unions; partners who are not household members) and at partner histories (never married, ever divorced, ever widowed, remarried), this study elaborates on previous research which has tended to look only at the presence versus the absence of partner relationships. Findings indicate that different types of partner relationships provide differential protection against loneliness. There appears to be a 'shadow of the past' of a previous divorce or widowhood in second and third partnerships, which accounts for generally higher levels of loneliness. Single men tend to be more lonely than single women. Moreover, there are no differences in loneliness between men who have always been single and those previously married. Among single women, differences in partner history are relevant: never married single women tend to be least vulnerable to loneliness. The differences in loneliness between older adults with different types of partner relationships and partner histories are only partially attributable to network and social participation differences. The latter independently contribute to the explanation of loneliness. The role of non-social determinants (health and socioeconomic position) is also examined. The results underscore the socially isolating effects of sensory impairments. Older adults with functional limitations, and those with visual or auditory problems tend to be more lonely, findings which are only partially attributable to differences in the number and quality of social relationships. Socioeconomic circumstances primarily have an indirect influence on loneliness. Those with higher levels of educational attainment and higher incomes tend to have more extensive social networks and are therefore less prone to loneliness.

[Living arrangements and social networks of elders. A selection of findings from a NESTOR-Study]. / Leefvormen en sociale netwerken van ouderen. Een selectie van bevindingen uit een NESTOR-Studie.

This article presents an overview of the design and results of the NESTOR survey 'Living Arrangements and Social Networks of Older Adults', an empirical study, started in 1992, among a representative sample of 4495 people, aged 55-89, selected from the population registers of 11 municipalities in the Netherlands. Questions were asked about living arrangements, the composition and functions of social networks, and important transitions in the marital, parental and occupational careers. The results indicated a wide diversity in living arrangements and social networks, a diversity which is particularly visible among the young old. They not only have larger networks, but are also more likely to live alone, to be divorced and to participate in shared housing arrangements. The networks vary considerably in size, from 0 to more than 40 important relationships. The decrease in network size with age appears to be directly related to specific life events such as widowhood, physical handicaps, residential moves etc. About 2/3 of the relationships are family relationships: parents, children (in law), grandchildren (in law), brothers and sisters (in law), uncles and aunts. Older people tend to be in touch at least once a month with the majority of close family members. The intensity of supportive exchanges (giving and receiving instrumental and emotional support in the twelve relationships with the highest levels of contact) is moderate, however mostly in balance. Only the very old receive somewhat more instrumental support and give considerably less than the 'young-old'. We studied the shift in balance between giving and receiving over a period of 12 months among a small proportion of the sample, checking a central hypothesis of exchange theory. In some cases a new balance evolves. In others the relationship continues to exist for a number of reasons, despite the imbalance. Early life experiences appear to be important for later life outcomes. Those who experienced the divorce of their parents before the age of 15 or those whose parents lived apart permanently (e.g. unmarried mothers) have a smaller social network and feel more lonely. Marital history has an impact on patterns of informal and formal care. E.g., those respondents without a partner who have children are less likely to use formal care than those who are childless. Among divorced elderly the use of formal care not only varies between men and women but also differs according to the marriage in which the children are born, first or second marriage. Occupational history is strongly related to the income level of older women living alone.

Loneliness among the never and formerly married: the importance of supportive friendships and a desire for independence.

Loneliness is an experience that is commonly associated with being old and without a partner. Results from a Dutch sample involving 131 unpartnered men and women between the ages of 65 and 75 indicate that the absence of friendship support rather than being single is an important determinant of loneliness. In accordance with the theory of mental incongruity, relationship standards and perceived opportunities of improving relationships are also shown to be significantly associated with loneliness. Older men and women without a partner are most vulnerable to loneliness when they have a high partner standard or a low singlehood standard, and see few opportunities to change their situation (for example, as a result of experienced health restrictions). A better understanding of loneliness is obtained if not only the quality of relationships is considered, but also the degree of congruity between relationships and relationship standards, and the favorability of perceived opportunities for bringing about improvements.

Safety, immunogenicity, and transmissibility of single-dose live oral cholera vaccine strain CVD 103-HgR in 24- to 59-month-old Indonesian children.

Recombinant A-B+ Vibrio cholerae O1 strain CVD 103-HgR is a safe, highly immunogenic, single-dose live oral vaccine in adults in industrialized countries. Safety, excretion, immunogenicity, vaccine transmissibility, and environmental introduction of CVD 103-HgR were investigated among 24- to 59-month-old children in Jakarta. In 81 households, 1 child was randomly allocated a single dose of vaccine (5 x 10(9) cfu) and another, placebo. Additionally, 139 unpaired children were randomly allocated vaccine or placebo. During 9 days of follow-up, diarrhea or vomiting did not occur more often among vaccines than controls. Vaccine was minimally excreted and was isolated from no controls and from 1 (0.6%) of 177 unvaccinated family contacts. A 4-fold or higher rise in serum vibriocidal antibody was observed in 75% of vaccines (10-fold rise in geometric mean titer over baseline). Of 135 paired placebo recipients or household contacts, 5 had vibriocidal seroconversions. Moore swabs placed in sewers and latrines near 97 households failed to detect vaccine. These observations pave the way for a large-scale field trial of efficacy.

[Friendships among the elderly]. / Vriendschappen van ouderen.

The present study examined whether the specific functions that are generally ascribed to friends, are also fulfilled by other types of close relationships. Semi-structured interviews were conducted with 46 men and women between the ages of 65 and 75, and living in their own homes. The majority of the romantic partners, sons (in-law), daughters (in-law), other relatives and neighbours were considered to be 'like friends'. Clear differences were found between the people who were friends or who were like friends, on the one hand, and the people who were not considered as such, on the other hand. People who were friends or like friends, shared more intimate feelings, and provided more self-esteem support and instrumental help. The findings indicate that relationships that have their origins in the family-network or in the neighbourhood, can play the role of friends. Older men and women should be encouraged to intensify these relationships.

Old and lonely?

The purpose of the present study was first, to assess the incidence of loneliness among older adults in light of gender, marital status, age and health, and second, to assess the associations between loneliness and a) descriptive characteristics and b) evaluations of the respondents' personal relationships. Interviews were conducted with 461 men and women, aged 65 and over, and living either at home or in institutions. The results show that it is necessary to examine the combined effects of marital status, gender, age and health in order to adequately assess the incidence of loneliness among older individuals. The study also reveals that an evaluation of the quality of personal relationships contributes more to the study of the incidence of loneliness than describing their characteristics.