On Improving Water-Based Drilling Mud Swelling Control Using Modified Poly(Vinyl Alcohol)s.

One of the most challenging issues when drilling under high-temperature, high-pressure (HT/HP) conditions is wellbore instability caused by clay swelling and fluid loss of the drilling mud. One of the most difficult issues when drilling under high-temperature, high-pressure (HT/HP) conditions is wellbore instability caused by clay swelling and fluid loss in drilling mud. Two modified PVOHs, nonionic and cationic polymers made from sodium bentonite clay and deionized water at concentrations of 0.08, 0.28, and 0.49 wt.%, were introduced to WBM percent. A series of specific gravity and mud rheology experiments at 25, 55, and 85 °C indicated that both values drop monotonically with increasing temperature, regardless of PVOH addition or concentration. A temperature increase of 30 °C decreases the mud viscosity of WBM (without PVOH) by 18% from its starting value, on average. Only 0.1% of cationic and nonionic polymer reduces viscosity by 10% and 0%, respectively. Experimenting with mud samples for 5 h revealed that adding nonionic polymers enhances mud filtration by up to 34.7%, 1.25 times more than that achieved from cationic polymers under the same filtration circumstances. Increasing the filtration temperature moderately affects mud cake generation due to increased mud swelling index and preferential adsorption by nonionic polymer. The latter observation was corroborated by determining the polymer content of the filtrates. Therefore, it was shown that nonionic polymers adsorbed more (118.9 mg/g) than cationic polymers (84.51 mg/g). Increased filtration temperature moderately affects mud cake generation due to increased mud swelling index and preferential adsorption by nonionic polymer. The latter observation was corroborated by testing the filtrates for the polymer content. As a result, it was discovered that nonionic polymer adsorbed more (118.9 mg/g) than cationic polymer (84.51 mg/g). Thermogravimetry analysis (TGA) finally tested the thermal stability of polymers.

Experimental Study on Enhanced Methane Detection Using an MEMS-Pyroelectric Sensor Integrated with a Wavelet Algorithm.

An optical sensing approach that balances portability with cost efficiency has been designed for the reliable monitoring of fugitive methane (CH4) emissions. Employing a LiTaO3-based pyroelectric detector integrated with micro-electro-mechanical systems and a broad infrared source, the developed gas sensor adeptly measured CH4 concentrations with a low limit of detection of about 5.6 ppmv and showed rapid response times with t90 consistently under 3 s. Notably, the novelty of our method lies in its precise control and reduction of CH4 levels, enhanced by wavelet denoising. This technique, optimized through meticulous grid search, effectively mitigated noise interference noticeable at CH4 levels below 10 ppmv. Postdenoising, nonlinear regression analyses based on the modified Beer-Lambert equation returned R2 values of 0.985 and 0.982 for the training and validation sets, respectively. In conclusion, this gas sensor has been shown to be able to meet the requirements for early warning of CH4 leakage on the surface in various carbon capture, utilization, and storage projects such as enhanced oil or gas recovery projects using CO2 injection.

Production, characterization, and application of Pseudoxanthomonas taiwanensis biosurfactant: a green chemical for microbial enhanced oil recovery (MEOR).

Biosurfactants, as microbial bioproducts, have significant potential in the field of microbial enhanced oil recovery (MEOR). Biosurfactants are microbial bioproducts with the potential to reduce the interfacial tension (IFT) between crude oil and water, thus enhancing oil recovery. This study aims to investigate the production and characterization of biosurfactants and evaluate their effectiveness in increasing oil recovery. Pseudoxanthomonas taiwanensis was cultured on SMSS medium to produce biosurfactants. Crude oil was found to be the most effective carbon source for biosurfactant production. The biosurfactants exhibited comparable activity to sodium dodecyl sulfate (SDS) at a concentration of 400 ppm in reducing IFT. It was characterized as glycolipids, showing stability in emulsions at high temperatures (up to 120 °C), pH levels ranging from 3 to 9, and NaCl concentrations up to 10% (w/v). Response surface methodology revealed the optimized conditions for the most stable biosurfactants (pH 7, temperature of 40 °C, and salinity of 2%), resulting in an EI24 value of 64.45%. Experimental evaluations included sand pack column and core flooding studies, which demonstrated additional oil recovery of 36.04% and 12.92%, respectively. These results indicate the potential application of P. taiwanensis biosurfactants as sustainable and environmentally friendly approaches to enhance oil recovery in MEOR processes.

Examination of the Factors Inhibiting CO2 Adsorption on Coal: A Case Study from Shallow-Depth Low-Rank Coal Seams.

Understanding the inhibitory factors affecting the adsorption of CO2 on low-rank coal from shallow-depth coal seams is essential to identify potential coal seams for CO2 sequestration. The CO2 adsorption capacity of shallow-depth coals was measured at a low pressure on raw and dry coals. The samples were also prepared for organic analyses, scanning electron microscopy analyses, and low-temperature nitrogen adsorption analyses to evaluate the CO2 adsorption and identify the inhibitory factors. An investigation was conducted to determine how CO2 adsorption occurs on coal by fitting experimental data to adsorption isotherm models, followed by analyzing the results based on the statistical analysis. In addition, this study used Henry's law, surface potential, and Gibbs free energy to identify the adsorption inhibitor between CO2 and coal. The CO2 adsorption experiment was conducted on raw coal with a moisture content of 15.18-20.11% and dry coal with no moisture. The experimental data showed that the CO2 adsorption capacity in dry coal was 1.6-1.8 times greater than that in raw coal. A fitting graph between the adsorption data and the isotherm model indicated that CO2 adsorption on coal occurred on monolayers and multilayers under raw and dry conditions. Statistical evaluation of the adsorption isotherm models showed that the Langmuir and Freundlich models aligned more closely to the experimental data. According to this result, low-pressure adsorption of CO2 on coal occurred in monolayers and multilayers under raw and dry conditions. Coal containing a high huminite content had a higher potential for CO2 adsorption, and the drying increased the positive relationship. On the other hand, coal containing high inertinite content inhibited CO2 adsorption onto the coal, but the drying process did not adversely affect CO2 adsorption. Furthermore, coal with high moisture and inertinite content inhibited the affinity, accommodation, and spontaneous CO2 adsorption onto the coal. CO2 adsorption could lead to swelling, but moisture loss opened more sites and micropores, resulting in the swelling effect not closing all micropores in dry coal. Based on these results, coal seams with low moisture and inertinite content are the most promising for CO2 adsorption. Altogether, this study provides an understanding of the percentage of inhibitor factors that affects CO2 adsorption on low-rank coal from shallow depths, which may lead to different CO2 adsorption capacities.

Nanobubbles activate anaerobic growth and metabolism of Pseudomonas aeruginosa.

The effect of nanobubbles on anaerobic growth and metabolism of Pseudomonas aeruginosa was investigated. P. aeruginosa grew earlier in the culture medium containing nanobubbles and the bacterial cell concentration in that culture medium was increased a few times higher compared to the medium without nanobubbles under anaerobic condition. Both gas and protein, which are the metabolites of P. aeruginosa, were remarkably produced in the culture medium containing nanobubbles whereas those metabolites were little detected in the medium without nanobubbles, indicating nanobubbles activated anaerobic growth and metabolism of P. aeruginosa. The carbon dioxide nanobubbles came to be positively charged by adsorbing cations and delivered ferrous ions, one of the trace essential elements for bacterial growth, to the microbial cells, which activated the growth and metabolism of P. aeruginosa. The oxygen nanobubbles activated the activities of P. aeruginosa as an oxygen source.

New Method to Predict the Viscosity of Bitumen Diluted with Light Oil Using a Modified Van Der Wijk Model under Reservoir Temperature and Pressure.

In this study, we introduce a new method for the prediction of the viscosity of bitumen diluted with light oil under reservoir temperature and pressure. This two-step method works as follows: first, predicting the bitumen viscosity under reservoir temperature and pressure using the classical Mehrotra and Svrcek model, and then subsequently using it in the modified Van Der Wijk (MVDM) model. This model formed from the modification of the original Van Der Wijk model was developed from the consideration of the interactions between like molecules in different binary components of the mixture. In this study, the bitumen viscosity was predicted with an average absolute deviation percentage (AAD%) of 3.86. The accuracy of the MVDM was investigated from the experimental results obtained from the rheological studies of three binary mixtures of light oil (API 32°) and bitumen (API 7.39°). Dead oils were mixed on a mass fraction basis. The viscosity was measured at a temperature range of 45-110 °C and a pressure range of 0.1-6 MPa. For comparison purposes, a reworked Van Der Wijk model (RVDM) was used in the same method and compared to the MVDM. The latter was more accurate than the RVDM with AAD% values of 8.88, 8.02, and 5.07 in predicting the viscosity of the three mixtures of 25, 32.5, and 50% bitumen with light oil. On the other hand, the RVDM had AAD% values of 12.42, 11.43, and 7.87 for the same mixtures, respectively. The applicability of this method was further verified by comparing its accuracy to another reported method using published data and it was found that the MVDM had AAD% values of 1.86, 6.55, and 2.823 when predicting the viscosities of the three mixtures under reservoir temperature and pressure conditions.

Formation Damage Induced by Water-Based Alumina Nanofluids during Enhanced Oil Recovery: Influence of Postflush Salinity.

Injecting nanofluids (NFs) has been proven to be a potential method to enhance oil recovery. Stranded oil is produced by wettability alteration where nanoparticles form a wedge film on pore wall surfaces, which is thought to shrink the pore space of the reservoir. Furthermore, ensuring the stability of the injected NF during the application is a major challenge. A low permeability reservoir and salinity of water make the response of NF injection to the formation damage more difficult. This article, therefore, studied the formation damage induced by the injection of alumina nanofluids (Al-NFs) in a relatively low permeability (7.1 mD) sandstone core. The salinity of the postflush water was also considered to mitigate the destructive impact. Al-NF was formulated by dispersing alumina nanoparticles (Al-NPs) in an aqueous solution of sodium dodecylbenzene sulfonate (SDBS) at its critical micelle concentration (CMC, 0.1 wt %). The formation damage, inherent to Al-NF injection, was evaluated by core-flooding tests. The assays consisted of the injection of 1 PV Al-NF (0.05 wt %) at the trail of which postflush at different salinities was flooded. The study found that the salinity of the postflush has an effect on the formation damage and oil recovery factor (RF). A chase water with a salinity concentration of 3 wt % sodium chloride (NaCl) produced an RF of 8.7% compared to a base case of water-flooding with a pressure drop of up to 13 MPa across the core (70 mm in length). These results pertained to the deposition of Al-NPs at the injection end. However, lowering the postflush salinity to 1 wt % NaCl mitigated the formation damage as evidenced by the decrease in pressure (35%) and an increase in RF to 17.2%.

Application of artificial neural network for predicting the performance of CO2 enhanced oil recovery and storage in residual oil zones.

Residual Oil Zones (ROZs) become potential formations for Carbon Capture, Utilization, and Storage (CCUS). Although the growing attention in ROZs, there is a lack of studies to propose the fast tool for evaluating the performance of a CO2 injection process. In this paper, we introduce the application of artificial neural network (ANN) for predicting the oil recovery and CO2 storage capacity in ROZs. The uncertainties parameters, including the geological factors and well operations, were used for generating the training database. Then, a total of 351 numerical samples were simulated and created the Cumulative oil production, Cumulative CO2 storage, and Cumulative CO2 retained. The results indicated that the developed ANN model had an excellent prediction performance with a high correlation coefficient (R2) was over 0.98 on comparing with objective values, and the total root mean square error of less than 2%. Also, the accuracy and stability of ANN models were validated for five real ROZs in the Permian Basin. The predictive results were an excellent agreement between ANN predictions and field report data. These results indicated that the ANN model could predict the CO2 storage and oil recovery with high accuracy, and it can be applied as a robust tool to determine the feasibility in the early stage of CCUS in ROZs. Finally, the prospective application of the developed ANN model was assessed by optimization CO2-EOR and storage projects. The developed ANN models reduced the computational time for the optimization process in ROZs.

Estimating a baseline of soil CO2 flux at CO2 geological storage sites.

This study aims to determine a baseline for natural soil carbon dioxide (CO2) flux at the surface based on long-term field measurements, with the ultimate purpose to detect the gas leakage at CO2 geological storage sites. CO2 surface monitoring is a tool that measures the safety and effectiveness of CO2 capture and storage (CCS), a technology which is believed to be a reliable approach to mitigate the CO2 emission. However, the fluctuations of naturally occurring CO2 in soil layers complicate the leakage detection as the soil connects both the underground layers and the atmosphere. In this regard, this study not only investigates the natural surface CO2 flux behavior but also develops an equation to estimate the surface CO2 flux with respect to the soil moisture content and temperature. To meet this end, two values within the CO2 flux equation were defined and calculated based on the field measurements; a, representing a water saturation-dependent value, and b, representing the temperature sensitivity (independent of the water saturation). The results show a good agreement between estimated and measured data. Upon which, the maximum baseline for surface CO2 flux was derived and used as a threshold to detect the potential CO2 leakage in the candidate field (INAS, Japan).

Gold Dissolution from Ore with Iodide-Oxidising Bacteria.

Gold leaching from ore using iodide-iodine mixtures is an alternative to gold cyanidation. This study evaluated the ability of iodide-oxidising bacteria to solubilise gold from ore that was mainly composed of gold, pyrite, galena, and chalcopyrite. Eight bacterial strains were successfully isolated from brine. Those strains were incubated in a liquid culture medium containing ore with a gold content of 0.26 wt.% and pulp density of 3.3 w/v% to evaluate their abilities to mediate the dissolution of gold. The gold was solubilised completely within 30 days of incubation in the iodine-iodide lixiviant solution generated by three bacterial strains. One strain, in particular, completed the dissolution of gold within 5 days of incubation and was identified as a member of the genus Roseovarius. Thus, the possibility of bacterial gold leaching using iodide-oxidising bacteria was successfully demonstrated. Bioleaching gold with iodide would likely be more environmentally sustainable than traditional cyanide leaching. Further research is required to evaluate the techno-economic feasibility of this approach.

Petrotoga japonica sp. nov., a thermophilic, fermentative bacterium isolated from Yabase Oilfield in Japan.

A gram-negative, motile, fermentative, thermophilic bacterium, designated AR80(T), was isolated from a high-temperature oil reservoir in Yabase Oilfield in Akita, Japan. Cells were rod-shaped, motile by means of polar flagella, and formed circular, convex, white colonies. The strain grew at 40-65 °C (optimum 60 °C), 0.5-9 % (w/v) NaCl (optimum 0.5-1 %), pH 6-9 (optimum pH 7.5), and elemental sulfur or thiosulfate serves as terminal electron acceptor. Phylogenetic analysis of 16S rRNA gene sequences indicated that strain AR80(T) belonged to the genus Petrotoga and shared approximately 94.5 % sequence similarity with the type species of this genus. The G + C content of genomic DNA was 32.4 mol% while the value of DNA-DNA hybridization between the closest relative species Petrotoga miotherma and AR80(T) was 58.1 %. The major cellular fatty acids of strain AR80(T) consisted of 18:1 w9c, 16:0, and 16:1 w9c. Based on genetic and phenotypic properties, strain AR80(T) was different with other identified Petrotoga species and represents as a novel species, for which the name Petrotoga japonica sp. nov. is proposed. The type strain is AR80(T) (=NBRC 108752(T) = KCTC 15103(T) = HUT 8122(T)).

Prevalence of pain among residents in Japanese nursing homes: a descriptive study.

It is often observed that pain causes substantial problems for nursing home residents. However, there has been little research about the prevalence of pain for nursing home residents in Japan. This study aimed to examine the prevalence of pain in older adults living in nursing homes in Japan by using self-reporting and the Abbey Pain Scale-Japanese version (APS-J) and to explore factors related to pain. This is a descriptive study. Residents in two Special Nursing Homes for the Elderly in Tokyo, Japan, were asked to participate in this study, with the exclusion of short-term temporary residents. Data collected from participating residents included their demographics and the results from the Barthel Index, the Folstein Mini-Mental State Examination, the APS-J, and the Verbal Descriptor Scale for pain. The residents were divided into two groups: residents able to report their pain (self-report group) and residents not able to report their pain. The second group was assessed by using the APS-J (APS-J group). The Mann-Whitney U test, the χ2 test, and logistic analyses were performed to derive factors related to pain prevalence. Data were obtained from 171 residents. The prevalence of pain in the self-report group (n = 96) was 41.7%. For the 75 residents unable to report their pain, 52.0% were assessed by the APS-J to have pain. The overall pain prevalence of all residents was 46.2%. Age, Barthel Index score, and length of time of institutionalization were significantly associated with residents' pain in the APS-J group. Logistic regression analysis showed that contracture (odds ratio 3.8) and previous injury (odds ratio 3.4) were associated with residents' pain in the self-report group, whereas only the length of nursing home stay (odds ratio 1.03) was a predictor for pain in the APS-J group. Nearly one-half of residents had pain when they moved or were moved. Pain assessment and management is needed for residents.

Microbial consortia in Oman oil fields: a possible use in enhanced oil recovery.

Microbial enhanced oil recovery (MEOR) is one of the most economical and efficient methods for extending the life of production wells in a declining reservoir. Microbial consortia from Wafra oil wells and Suwaihat production water, Al-Wusta region, Oman were screened. Microbial consortia in brine samples were identified using denaturing gradient gel electrophoresis and 16S rRNA gene sequences. The detected microbial consortia of Wafra oil wells were completely different from microbial consortia of Suwaihat formation water. A total of 33 genera and 58 species were identified in Wafra oil wells and Suwaihat production water. All of the identified microbial genera were first reported in Oman, with Caminicella sporogenes for the first time reported from oil fields. Most of the identified microorganisms were found to be anaerobic, thermophilic, and halophilic, and produced biogases, biosolvants, and biosurfactants as by-products, which may be good candidates for MEOR.

Evaluation of a Japanese version of the Mini-Mental State Examination in elderly persons.

AIM: This study aimed to examine the validity and item-response characteristics of the Mini-Mental State Examination (MMSE), which is used for assessing cognitive function, in Japanese older adults. METHODS: Factor analysis and item response analysis were carried out for MMSE responses (n = 1971) from older adults living in the community (n = 1339) or in a nursing home (n = 632), including Alzheimer-type dementia (n = 330), vascular dementia (n = 36), frontotemporal dementia (n = 7), mixed Alzheimer-type and frontotemporal type dementia (n = 27), and age-related cognitive decline (n = 29). When choosing the cut-off score of 23 points for the MMSE, sensitivity and specificity for each item were calculated. RESULTS: A three-factor solution was found to be most appropriate by factor analysis: complex processing, simple processing and working memory. The item characteristics curves showed unidimensionality with high reproducibility. We identified a simplified scale comprising 10 items in all participants: "naming", "three-step command", "registration", "repeat a sentence", "write a complete sentence", "copies drawing of two polygons", "orientation to place", "delayed recall", "orientation to time" and "serial sevens" tasks. Sensitivity and specificity for both "year" task and "day" task were more than 90% ("year": sensitivity 92.5%, specificity 96.3%; "day": sensitivity 92.4%, specificity 91.7%). For the Alzheimer-type dementia patients, the five-factor solution was suggested by factor analysis and the MMSE also had unidimensionality in terms of level of difficulty. CONCLUSIONS: We found that the MMSE had multiple cognitive areas. We showed that the MMSE could be used as an essentially unidimensional measure of cognitive ability and the question about orientation to time might be useful in the simplest assessment to identify cognitive dysfunction.

Psychometric properties of the Caregiving Burden Scale for Family Caregivers with Relatives in Nursing Homes: scale development.

AIM: Most family caregivers continue their caregiving for frail relatives after admitting them to long-term care facilities. The characteristics of this caregiving differ from those related to caregiving in home-care settings. Thus, a new tool to evaluate the burden of family caregivers in institutional settings is needed. The aim of this study was to develop a new scale, the Caregiving Burden Scale for Family Caregivers with Relatives in Nursing Homes, and to confirm its validity and reliability. METHODS: We conducted two cross-sectional questionnaire surveys. The participants were a convenience sample of family members of residents in seven nursing homes for the validation study and in three nursing homes for the test-retest study in Japan. Statistical analyses examined exploratory/confirmatory factor analyses, internal consistency, concurrent/discriminate validity, and test-retest reliability. RESULTS: A four-factor solution with 16 items was selected as the most interpretable questionnaire. In the confirmatory factor analysis, the indices of fitness highly supported these results. The Cronbach's alpha coefficient for the total score was 0.86 and varied between 0.77 and 0.87 in the four domains. The scale showed moderate correlation with the Nursing Home Hassles Scale, suggesting its concurrent validity. The four domains had only a medium correlation with each other, indicating discriminate validity. CONCLUSIONS: The developed scale has acceptable validity and reliability for measuring the caregiving burden of family members with relatives in Japanese nursing homes. Future studies using the scale might lead to the improvement of care for family members with relatives in a long-term care setting.

Abbey Pain Scale: development and validation of the Japanese version.

AIM: The purpose of this study was to develop and validate the Japanese version of the Abbey Pain Scale (APS-J), to assess pain of older adults who live in nursing homes in Japan. METHODS: In this study, the data were collected from residents in two nursing homes in Japan to include: demographics, the Barthel Index, Folstein Mini-Mental Examination (MMSE), APS-J and Verbal Descriptor Scale (VDS) for pain. Two researchers independently assessed the residents' pain using the APS-J while the residents walked or were transferred from bed to wheelchair. Intraclass correlation coefficients (ICC) for inter-rater and test-retest reliability, Chronbach's alpha-value of the APS-J, and correlation between the APS-J and other variables were examined. RESULTS: Data were obtained from 171 residents. The ICC for inter-rater and test-retest reliability were 0.824 and 0.657, respectively. Internal consistency was 0.645 for the total sample and 0.719 for those with an MMSE score of 0 (n = 58). Multiple regression analysis showed that contractures (P < 0.001), previous injuries (P < 0.001), the MMSE (P = 0.003) and paralysis (P = 0.018) were independently associated with the APS-J. The APS-J and VDS were moderately correlated (r = 0.49; P < 0.01). The APS-J total score and subscales, "change in body language" and "physical changes", were significantly different among subjects with different MMSE score groups. CONCLUSION: Findings show some evidence for the reliability and validity of APS-J.

Progressive supranuclear palsy combined with Alzheimer's disease: a clinicopathological study of two autopsy cases.

We present here the clinicopathological characteristics of two autopsy-confirmed cases comorbid of progressive supranuclear palsy (PSP) and Alzheimer's disease (AD). Histopathologically, the amount and distribution of neurofibrillary tangles (NFTs) in the basal ganglia and brainstem fulfilled the pathological criteria of PSP proposed by the National Institute of Neurological Disorders and Stroke--The Society for PSP (NINDS-SPSP). The Braak stages of senile plaques and NFTs were stage C and stage V in Case 1, and stage C and stage IV in Case 2. These neuropathological findings confirmed that the two patients had combined PSP with AD. Our patients presented clinically with executive dysfunction prior to memory disturbance as an early symptom. Not only neurological symptoms such as gait disturbance, supranuclear ophthalmoplegia and pseudobulbar palsy, but emotional and personality changes and delirium were prominent. Therefore, symptoms of subcortical dementia of PSP were more predominant than AD-related symptoms in the present two patients. Comorbid PSP and AD further complicates the clinical picture and makes clinical diagnosis even more difficult.

Factors related to family visits to nursing home residents in Japan.

This study examined factors related to the frequency and duration of family visits to elderly residents of nursing homes in Japan. Data were collected using a self-administered questionnaire from 299 family members of residents of three nursing homes in Tokyo. Almost all family members visited residents more than once a month, and more than three quarters stayed for more than 1h during each visit. These findings confirm that family involvement with the elderly is maintained even after admission to a nursing home. Multiple regression analysis revealed the variables related to a higher frequency and duration of visits. Some factors related to frequent or long visits such as the requirement of higher care or the ability to remember family visits were similar to the findings of other studies conducted in western countries, yet the results need to be understood in a Japanese cultural context. Other factors such as the gender of the visitors, distance to the nursing home, and sentiment about placement were thought to be related to the unique cultural norms of family caregiving in Japan. These findings will be useful for developing effective methods to assist nursing home residents and their families in Japan.

[Mental health and related factors with family caregivers for elderly in special-care nursing homes for the aged].

PURPOSE: The purpose of this study was to examine the mental health and related factors with family caregivers for the elderly in special-care nursing homes for the aged. METHODS: We conducted a questionnaire survey among family caregivers for elderly living in three special-care nursing homes in Tokyo. The questionnaire included factors from the General Health Questionnaire-28 (GHQ-28) pertaining to family caregivers, the elderly, and the relationships between them. The GHQ-28 was used to measure the mental health of the caregivers and a logistic regression model was applied for the analysis. RESULTS: Of the 145 family caregivers surveyed, 59 (40.7%) exhibited low mental health (GHQ-28> or = 7). The logistic regression analysis revealed that family caregivers with low mental health had lower social support (OR: 0.10 (0.03-0.29)) and had longer visiting times (OR: 5.80 (1.79-18.82)). DISCUSSION: The results suggested that many family caregivers for elderly persons in institutions may have poor mental health and that it is necessary to provide them with support. It is concluded that self-help groups for families and the promotion of communication between the elderly and their family caregivers might be effective for this purpose.