Chlorophyll Fluorescence Imaging for Environmental Stress Diagnosis in Crops

The field of plant phenotype is used to analyze the shape and physiological characteristics of crops in multiple dimensions. Imaging, using non-destructive optical characteristics of plants, analyzes growth characteristics through spectral data. Among these, fluorescence imaging technology is a method of evaluating the physiological characteristics of crops by inducing plant excitation using a specific light source. Through this, we investigate how fluorescence imaging responds sensitively to environmental stress in garlic and can provide important information on future stress management. In this study, near UV LED (405 nm) was used to induce the fluorescence phenomenon of garlic, and fluorescence images were obtained to classify and evaluate crops exposed to abiotic environmental stress. Physiological characteristics related to environmental stress were developed from fluorescence sample images using the Chlorophyll ratio method, and classification performance was evaluated by developing a classification model based on partial least squares discrimination analysis from the image spectrum for stress identification. The environmental stress classification performance identified from the Chlorophyll ratio was 14.9% in F673/F717, 25.6% in F685/F730, and 0.209% in F690/F735. The spectrum-developed PLS-DA showed classification accuracy of 39.6%, 56.2% and 70.7% in Smoothing, MSV, and SNV, respectively. Spectrum pretreatment-based PLS-DA showed higher discrimination performance than the existing image-based Chlorophyll ratio.

Fire retardant performance, toxicity and combustion characteristics, and numerical evaluation of core materials for sandwich panels

According to fire accident statistics, fires in buildings are increasing. The flame-retardant performance of insulation materials is considered an important factor for preventing the spread of fire and ensuring evacuation. This study evaluated the flame-retardant performance and combustion characteristics of four types of organic thermal insulation used as core materials in sandwich panels. The flame-retardant performance evaluation based on total heat release and heat release rate revealed that phenolic foam (PF) satisfied the criteria for non-combustible grade insulation. An analysis of the hazardous gases released while combustion of the four insulation materials indicated that a significant amount of CO was released-an average of 19,000 ppm or higher-in the rigid urethan foam (PIR) and spray-type polyurethane foam (SPU). The fractional effective dose (FED) value was derived from the gas analysis results according to ISO 13344. PIR and SPU had an average FED value of 2.0 or higher and were identified as very dangerous in the case of fire accidents. Moreover, the evacuation time in the case of a fire in a warehouse-type building was comprehensively analyzed considering the material, size, and height for the four types of insulation. PIR was the most vulnerable to fire, and for PF, the danger limit was not reached until the end of the simulation.

Passive PM2.5 control plan of educational buildings by using airtight improvement technologies in South Korea

Modern people spend most of their time indoors. Therefore, controlling indoor air quality is one of the most important factors for health. The indoor fine dust concentration is affected by the outdoor fine dust concentration. When the latter is high, it increases due to immersion. Therefore, improving the sealing performance of a building is an effective strategy to reduce indoor fine dust concentration during periods of severe outdoor fine dust without considering indoor fine dust generating factors. Traditional methods of improving the airtightness of a building have focused on replacing windows or doors. However, for reasons such as constructability and economic feasibility, more diverse technologies need to be considered. Due to this necessity, this study applied technologies such as sealing film, sealing lid, and padding to the educational building, and then derived the airtight performance through the blower door experiment, and measured the fine dust concentration to evaluate the effect. As a result of the experiment, it was analyzed that air leakage was reduced by up to 37% and fine dust by 22%.

Practical solutions with PCM for providing thermal stability of temporary house, school and hospital in disaster situations

Globally, humanity is at risk from the coronavirus disease (COVID-19). To address the shortage of beds in quarantining those infected with COVID-19, hospitals have prepared temporary beds. However, for temporary hospital beds, it is difficult to maintain a comfortable temperature due to lack of insulation and heat storage. Phase change materials (PCMs) are used to provide temperature stability and control for temporary structure. Therefore, this study aimed to conduct experiments that analyze the effect of room temperature stabilization using a PCM. The method of macro packed PCM (MPPCM) was used to apply the PCM to buildings. The MPPCM installation location was selected and the effect of reducing the box temperature was analyzed, according to the strength of the heat source. As a result, a maximum reduction of 4.9 °C in the box temperature was achieved. Therefore, the application of MPPCM to buildings give to stabilize the box temperature. And the result showed the possibility of providing a comfortable indoor space for temporary hospital beds.

Effect of eco-friendly pervious concrete with amorphous metallic fiber on evaporative cooling performance

Impervious pavements exist in large proportions in most cities owing to the high-impact development of the transportation infrastructure. However, this type of pavement causes environmental issues such as waterlogging, floods, and urban heat islands. Pervious concrete (PC), which is a novel pavement material characterized by a porous structure that allows water to percolate through it, is an important solution to these issues. This study investigates the evaporative cooling performance of eco-friendly PC with blast-furnace slag (BFS) as a cement replacement and amorphous metallic fiber (AMF) that helps to accelerate the evaporative cooling. The thermophysical properties, water permeability, and water absorption capability of the manufactured PC were measured. In addition, a scale model test and thermal conductivity analysis of the manufactured PC were conducted to evaluate the evaporative cooling effect. The results indicate that the physical and mechanical properties of the manufactured PC are typically similar to those of other PCs, and its water absorption rate reaches 1 mm/s. Relatively low water permeability helps the PCs to absorb more water, contributing to accumulate a large amount of water in the material for evaporative cooling. In addition, AMF contributes to increase thermal conductivity of PC, which allow the water inside the PCs to evaporate faster. The result shows that a higher thermal conductivity of the manufactured PC increases the evaporative cooling effect.

Hazard evaluation of indoor environment based on long-term pollutant emission characteristics of building insulation materials: An empirical study

Insulation materials are essential components in construction, and their main objective is to increase the efficiency of thermal energy by minimizing internal and external thermal exchange. Accordingly, research and development studies are being actively conducted to increase the thermal resistance of insulation materials, and high-performance insulation materials that use organic chemicals have been developed after industrialization. However, thermal insulation comprising chemicals poses a potential risk of pollutant emissions and can cause health problems. In this study, five types of insulation materials and the contaminants generated from the building materials used in insulation construction were quantitatively analyzed. In addition, an empirical study on the discharge of pollutants was conducted using a test bed, and the effects of the pollutants discharged from the insulation material on the indoor environment were examined by analyzing the pollutant concentration for 90 days. In addition, we analyzed the effect of an insulation material on an indoor environment through the standard specifications. Moreover, the necessity of legal management of the emission of contaminants from insulation materials was proposed based on the empirical research results.

Verification of particle matter generation due to deterioration of building materials as the cause of indoor fine dust

Particles of fine dust are pollutants that adversely affect indoor air quality and exacerbate human respiratory diseases. The aging of the building was pointed out as a source of fine dust indoors. The aging of buildings has various causes of deterioration. During various deterioration, friction adversely affects the building floor finish. In this study, an accelerated friction deterioration device was used to confirm the generation of fine dust particles through the frictional deterioration of floor finishes in buildings. The study found that the concentration of fine dust particles attributed to deteriorating flooring was 327 mg/m³ in PM2.5 and 4828 mg/m³ in PM10 and confirmed that particle distribution differs depending on the surface of the flooring. Particles of 10 µm or less were observed through particle analysis. The study confirmed that fine dust particles did not diffuse in a specific direction and that the detected fine dust particles could be attributed to deterioration. Further research is needed on the detection of fine dust in degraded building finishing materials.

Evaluation of thermal properties and acetaldehyde adsorption performance of sustainable composites using waste wood and biochar

In order to vitalize the use of wood, which is a sustainable resource, increase the utilization of resources through the recycling of wood waste, and reduce environmental pollution in the waste disposal process, biocomposite was manufactured by using biochar which can be produced with wood waste and is effective in carbon isolation. The thermal characteristics and acetaldehyde adsorption performance of the prepared biocomposite were evaluated based on the pore characteristics, surface functional groups, crystal structure, and elemental analysis results of the biochar. As a result of the experiment, as the content of biochar increased, the thermal conductivity of the biocomposite decreased and the specific heat was not affected. The acetaldehyde concentration tended to decrease as the content of biochar increased, adsorbed up to 4.4685 ppm of acetaldehyde more than the reference. From these results, it is judged that the biocomposite produced in this study can function as a sustainable composite that uses waste wood to improve indoor air quality and satisfies the performance as a building material.

A comparative analysis of biochar, activated carbon, expanded graphite, and multi-walled carbon nanotubes with respect to PCM loading and energy-storage capacities

To obtain high thermal performance composite phase change materials (PCMs), various other supporting materials have been utilized to encapsulate organic PCMs. In this study, four carbon materials (biochar, activated carbon, carbon nanotubes, and expanded graphite) were introduced to support heptadecane. The composite PCMs were designed using vacuum impregnation techniques. The structural stability, chemical compatibility, thermal stability, and thermal energy storage capacity of the as-prepared materials were systematically characterized using differential scanning calorimetry, Fourier-transform infrared spectroscopy, etc. Among the supporting materials, expanded graphite had a high PCM content of 94.5%, whereas it was low for biochar-supported PCM (25.7%). Meanwhile, the latent heat storage capacity ranged from 53.3 J/g to 195.9 J/g. It was observed that the intermolecular interactions between the PCM and supporting materials and the surface functionality of the encapsulating agents play a leading role in the thermal performance of the composite PCMs. Furthermore, pore structures such as specific surface area, total pore volume, and pore size distribution have a combined effect on the crystallinity of heptadecane in the composite PCMs. The study will provide insight into developing and designing carbon-based composite PCMs for heat-storage purposes.

Thermal, hygric, and environmental performance evaluation of thermal insulation materials for their sustainable utilization in buildings

As energy use in the building sector is increasing worldwide, building materials with characteristics that save energy are becoming increasingly important; in addition, there is an emerging need for high-performance insulation materials with low thermal conductivity. However, thermal insulation should consider thermal conductivity, which is the main performance parameter, in addition to the water adsorption rate, acidity, and deformation and expansion due to drying conditions. This study evaluated the main performance of 21 insulation materials used at construction sites to objectively and clearly evaluate their overall performance, including their thermal conductivity. Thermal conductivity was measured by the heat flow meter method according to ASTM C518 and ISO 8301 standards; it was also evaluated according to the drying conditions. The water absorption rate was evaluated by ISO 2896 to ensure the sustainability and long-term thermal conductivity performance of the material. Acidity was evaluated with ASTM E861 to reduce the environmental load of the buildings and soil. The results of this study reviewed an appropriate method to measure the main performance according to the type of insulation.

Evaluation of hygrothermal performance of wood-derived biocomposite with biochar in response to climate change

Wood is a sustainable resource and building material. It provides an excellent response to climate change and has excellent insulation performance. However, structural defects may occur due to decay from moisture, resulting in poor dimensional stability. The rich organic substances contained in wood can lead to mold when the moisture content is consistently high, adversely affecting the health of occupants. Therefore, we attempted to compensate for the disadvantages of wood in regard to water stability while maintaining the high thermal insulation performance and carbon dioxide storage capacity, using biochar from thermally decomposed spruce under oxygen limiting conditions. A wood-derived biocomposite was prepared by mixing biochar and soft wood-based chips using the hot-press method, and the thermal conductivity, specific heat, water vapor resistance factor, moisture adsorption, and moisture desorption performances were analyzed. The thermal conductivity of WB10 with 10 wt% biochar content was 0.09301 W/mK. This is a 7.98% decrease from 0.10108 W/mK, the thermal conductivity of WB0 without biochar. The water vapor resistance factor tended to increase when the biochar ratio increased. As the proportion of biochar increased, the equilibrium moisture content in high relative humidity tended to decrease, and it was found that the moisture adsorption and desorption performances were affected by the ratio of the biochar. Therefore, wood-derived biocomposites using biochar can be used in environmentally friendly materials, with improved thermal insulation performance and water stability.

Evaluation of environmental impact on the formaldehyde emission and flame-retardant performance of thermal insulation materials

Thermal insulation material, an essential building material, is used to preserve heat or block heat gains in buildings. Insulation material is currently attracting significant attention, and thermal conductivity, i.e., thermal insulation performance, is expressed at a very low value. Therefore, since the era of industrialization, several chemicals have been used to secure thermal insulation performance in each sector; therefore, the resulting hazards have increased. To date, researches have been mainly conducted to secure the low thermal conductivity of insulating material; however, the hazards remain unaddressed. Therefore, this study quantitatively evaluates 18 building construction products and the emission of pollutants and harmful gas during combustion events. Pollutant emission was conducted using the 20-L small chamber method according to the ISO 16000, and formaldehyde, total volatile organic compounds, and five volatile organic compounds were analyzed. Gas hazard evaluation during combustion was evaluated by KS F 2271: Fire Retardant Testing Method of Interior Finishes and Structures as the average behavioral stop time of rats under thermal insulation combustion conditions.

Numerical analysis on the hygrothermal behavior of building envelope according to CLT wall assembly considering the hygrothermal-environmental zone in Korea

As buildings generally have become larger and more airtight, the ventilation rate has decreased further, causing insufficient ventilation which leads to moisture problems such as condensation, mold growth, reduction of thermal insulation performance and corrosion of building materials. In order to prevent moisture problems, it is essential to understand the thermal and hygric status of a climatic region. In this study, the hygrothermal environmental zone considering not only the thermal environment but also the hygric environment was derived by analyzing the climate environment in Korea. The hygrothermal environmental zone has the advantage of being able to take into account the hygrothermal environment of the unexplored regions and to cope with climate change by quantifying the thermal and hygric environmental indexes in each region. Finally, the long-term moisture risk of the building envelopes was evaluated. As the results, it is considered that the proposed hygrothermal environmental zone is appropriate and it is necessary to consider the hygric environment in order to secure the moisture stability of the building envelope.

Microstructure and thermal characterization of aerogel-graphite polyurethane spray-foam composite for high efficiency thermal energy utilization

Aerogel is a superinsulating material with an extremely low thermal conductivity (<0.015 W/m·K), high porosity (>99 %), and extremely low density. In this study, a new closed-cell spray polyurethane (PU) foam with aerogel was developed and investigated. In particular, a PU foam with aerogel and graphite (PUAG) was prepared by mixing aerogel for reducing the thermal conductivity of the foam and a small concentration of graphite for improving its flame-retardancy performance. The performance of the prepared PUAG was analyzed via several tests, including density measurements, thermal-conductivity measurements, morphology examination, flame-retardancy evaluation, thermogravimetric analysis, and dynamic heat transfer analysis. A 20 % reduction in the thermal conductivity compared with traditional PU was observed. Additionally, the PUAG exhibited a reduction in the total smoke production and a 10 % reduction in the surface peak temperature.

Evaluation and analysis of volatile organic compounds and formaldehyde emission of building products in accordance with legal standards: A statistical experimental study

Building materials have been developed mainly for thermal performance, strength, low energy consumption, and aesthetics. Consequently, large amounts of chemicals have been added to building products, resulting in the release of abundant pollutants that adversely affect human health. In particular, pollutants from the materials used to build modern dwellings can cause sick house syndrome, which leads to health resilience problems and diseases. In this study, more than 100 investigations were conducted annually from 2004 to 2017 by using the 20 L small chamber method to analyze the contents of formaldehyde (HCHO) and total volatile organic compounds (TVOC) released from 2780 building products in total. High emissions were released by some building components with raw materials containing hazardous chemicals. However, since the 2004 enactment of a legal standard for the regulation of emissions of harmful substances in building products, the pollutant emissions have tended to decrease over the years. As a result of the experiment, all 2780 building materials met the legal standard on average. Therefore, legal restrictions on the release of hazardous materials from building products have achieved reductions in pollutant emissions.

Field study on the improvement of indoor air quality with toluene adsorption finishing materials in an urban residential apartment

To improve the indoor air quality of apartments in Korea, a toluene adsorptive paint was manufactured and tested for its efficiency to remove the indoor toluene released from wallpaper adhesives. The toluene adsorptive paint was prepared by blending activated carbon and inorganic binder, and the pore characteristics and chemical functional groups of the activated carbon were analyzed to determine whether the micropores and surface functionalities of activated carbon affected toluene adsorption. Toluene adsorption performance of the toluene adsorptive paint was confirmed through static and verification experiments. The average adsorption efficiency of toluene adsorptive paint in the static experiment was 98.3% and the verification experiment confirmed that about 96.3% of toluene was adsorbed from the indoor air of the apartment. As a result, the use of toluene adsorptive paint effectively removes toluene, which may occur in the adhesive, and thus can be considered to have a good effect on the improvement of indoor air quality. Furthermore, toluene adsorptive paint has been found to be an effective way to achieve consumer wall finishing preferences and maintenance convenience.

Characterization of biocomposite using coconut oil impregnated biochar as latent heat storage insulation

Objective of this research was to characterize properties of the latent heat storage biocomposite (LHSBC) as a novel material that can be employed as a latent heat storage insulation by using biochar. Biochars produced from waste material pine cone, pine saw dust, and paper mill sludge were vacuum impregnated with a bio-based phase change material (PCM), coconut oil, to prepare LHSBCs. In particular, this paper analyzed the chemical stability, latent heat storage performance, thermal conductivity, and thermal stability of LHSBCs based on results of fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), laser flash method and thermogravimetric analysis (TGA). As a result, the LHSBCs showed a maximum latent heat storage capacity of 74.6 J/g and a low thermal conductivity of 0.030 W/mK at the maximum, confirming that LHSBCs have a high latent heat storage capacity and thermal insulation performance. With a maximum specific heat of 1.69 J/gK, a high, sensible heat storage was confirmed. In addition, all LHSBCs were found to be thermally and chemically stable. The LHSBC could be employed as a material with good thermal insulation performance and heat storage characteristics.

Spent coffee grounds as supporting materials to produce bio-composite PCM with natural waxes

Novel kinds of bio composite Phase change materials were prepared by the use of bio-wastes. Of the by-products, coffee wastes, which is currently consumed and abandoned as coffee as a drink, was used as the supporting material for PCM. It was found through chemical composition of FTIR of SCBW, SCPW, SCGW and that the coffee wastes were effectively vacuum impregnated into each natural wax. As a result of TGA, the thermal stability of SCBW, SCPW, SCGW and SCNW was checked. In addition, the DSC results were used to determine the heat storage performance of each material. Micro-morphological analysis with FE-SEM showed whether the impregnation was successful. The use of bio-compatible PCM by-products is economical as well as environmentally friendly and is sufficient for building applications in terms of thermal performance compared to other bio-composites.

Assessment of recycled ceramic-based inorganic insulation for improving energy efficiency and flame retardancy of buildings

In addition to the mitigation of carbon emissions through the reduction of building energy consumption, the prevention of fire spread in buildings is important an important task globally. Therefore, a growing interest towards building materials that can simultaneously contribute to energy savings and provide good flame-retardant performance in buildings exist. The flame-retardant performances of buildings can be improved through the use of inorganic building materials during construction. Meanwhile, among the different types of construction waste, more than 70% of ceramics can be recycled, which would reduce carbon emissions in the production process. Ceramics are inorganic and non-flammable, and can thus secure the flame-retardant performance of buildings. In this study, recycled ceramic-based inorganic insulation to secure the flame-retardant performance of a building are analyzed for their energy saving values. A case study building was modeled and the flame-retardant performance and building energy consumption were analyzed. Setting the thermal transmittance of the external wall according to the energy conservation design standards in South Korea, the tradeoff between model calculates annual energy consumption fire protection and minimization of material environmental impacts are discussed. As a result of simulation, when a wall constructed according to the energy conservation design standards of buildings, the building energy was saved by 18.6% and fire resistance performance was secured.

Dynamic heat transfer and thermal performance evaluation of PCM-doped hybrid hollow plaster panels for buildings

The thermal performance of hybrid hollow plaster panels (HHPPs) was analyzed using the amount of phase change material (PCM) injection as a variable according to the size of the hollow area. This study focuses on n-octadecane, an organic PCM that is used for storing latent heat during the phase change range and to improve thermal transmittance using exfoliated graphite nanoplatelets (xGnPs), which have a high thermal conductivity. When xGnP is applied to n-octadecane, the thermal conductivity improves by 225%, and it is confirmed that the thermal storage or release of the phase change material is an active reaction. The thermo-physical properties of the xGnP and n-octadecane composites were analyzed using a thermal conductivity analyzer (TCi) and differential scanning calorimetry (DSC). The thermal stability of PCM was analyzed over a long duration of 10,000 thermal cycles. The thermal performance of the PCM/plaster composite panel using the dynamic heat transfer device was determined. The peak temperature through the HHPP significantly reduced by 3.8 ℃ in an internal room, and the time-lag effect was confirmed to be 1.56 h. The results indicate that up to 36.6 J/m² of thermal energy was stored in the 26-Px/O, corresponding to approximately 247% of the available thermal energy of the reference panel.

Biochar-red clay composites for energy efficiency as eco-friendly building materials: Thermal and mechanical performance

Biochar and red clay were used to develop eco-friendly building materials with improved thermal and mechanical performance. Rice husk, coconut shell, and bamboo were prepared by thermally decomposing as biochar. Thermal conductivity measurements, scanning electron microscopy imaging, compressive strength measurements, and an infrared heat transfer experiment were performed, and the results showed that the mixture of biochar tends to lower the thermal conductivity. The compressive strength of specimens mixed with rice husk decreased, but that of specimens mixed with coconut shell and bamboo tended to increase. The infrared heat transfer test showed that the thermal performance of the mixed rice husk specimens was significant, while the specimen mixed with coconut shell and bamboo showed thermal performance improvement. A comprehensive evaluation of the improvement in thermal performance and strength indicated that a 10 wt.% mixture of bamboo was the most effective. Therefore, it was possible to effectively determine the type and weight ratio of biochar to red clay binder an important step in the study of biochar and red clay building materials.

Latent heat storage biocomposites of phase change material-biochar as feasible eco-friendly building materials

One approach to enhance the energy efficiency of buildings is the integration of construction materials of latent heat storage biocomposites, which are prepared by vacuum impregnating the phase change material into biochar. Biochar is used because it is highly utilized and environmentally-friendly, and the selected phase change materials are fatty acid type which are bio-based material and have a low risk of depletion. Experimental results showed that latent heat storage biocomposite possesses excellent exudation and thermal stability as characterized by 0.1727 W/mK of thermal conductivity comparable to that for a gypsum board, and good chemical compatibility as its amount of latent heat tends to decrease as compared with that of pure phase change material. Results of the numerical analysis showed further that latent heat storage biocomposite efficiently reduced the maximum energy consumption of reference building models by 531.31 kWh per year. Thus, both results validate the claim that latent heat storage biocomposite is a promising building material.

Evaluation of Toluene Adsorption Performance of Mortar Adhesives Using Porous Carbon Material as Adsorbent

Porous carbon materials are advantageous in adsorbing pollutants due to their wide range of specific surface areas, pore diameter, and pore volume. Among the porous carbon materials in the current study, expanded graphite, xGnP, xGnP C-300, xGnP C-500, and xGnP C-750 were prepared as adsorbent materials. Brunauer–Emmett–Teller (BET) analysis was conducted to select the adsorbent material through the analysis of the specific surface area, pore size, and pore volume of the prepared porous carbon materials. Morphological analysis using SEM was also performed. The xGnP C-500 as adsorbent material was applied to a mortar adhesive that is widely used in the installation of interior building materials. The toluene adsorption performances of the specimens were evaluated using 20 L small chamber. Furthermore, the performance of the mortar adhesive, as indicated by the shear bond strength, length change rate, and water retention rate, was analyzed according to the required test method specified in the Korean standards. It was confirmed that for the mortar adhesives prepared using the xGnP C-500 as adsorbent material, the toluene adsorption performance was excellent and satisfied the required physical properties.

Evaluation of the Adsorption Performance and Sustainability of Exfoliated Graphite Nanoplatelets (xGnP) for VOCs

Exfoliated graphite nanoplatelets (xGnP), which combine the layered structure and low price of nanoclays with the superior mechanical, electrical, and thermal properties of carbon nanotubes, are very cost-effective, and can simultaneously provide a multitude of physical and chemical property enhancements. In this study, we evaluated xGnP’s adsorption performance of volatile organic compounds (VOCs) according to thermal extractor (TE) analysis for seven days in order to use the xGnP as an adsorption material of pollutants. In addition, we carried out a sustainability evaluation in order to evaluate its adsorption capacity over 28 days. The results indicate that the adsorption performance of xGnP is higher than for other adsorption materials such as zeolite. Also, we determined that the adsorption performance of xGnP is maintained continuously for 28 days and that its adsorption capacity is large.

Heteronuclear recoupling in solid-state magic-angle-spinning NMR via overtone irradiation

A heteronuclear dipolar recoupling scheme applicable to I-S spin pairs undergoing magic-angle-spinning (MAS) is introduced, based on the overtone irradiation of one of the coupled nuclei. It is shown that when I is a quadrupole, for instance (14)N, irradiating this spin at a multiple of its Larmor frequency prevents the formation of MAS dipolar echoes. The ensuing S-spin signal dephasing is significant and dependent on a number of parameters, including the I-S dipolar coupling, the magnitude of I's quadrupolar coupling, and the relative orientations between these two coupling tensors. When applied to a spin-1 nucleus, this overtone recoupling method differs from hitherto proposed recoupling strategies in that it involves only the +/-1> I(z) eigenstates. Its dephasing efficiency becomes independent of first-order quadrupolar effects yet shows a high sensitivity to second-order offsets. A constant-time/variable-offset recoupling sequence thus provides a simple route to acquire, in an indirect fashion, (14)N overtone spectra from rotating powders. The principles underlying this kind of S-(14)N experiments and different applications involving S = (13)C, (59)Co sites are presented.

Maternal pre-eclampsia/eclampsia and the risk of sudden infant death syndrome in offspring

To determine whether maternal exposure to pre-eclampsia/eclampsia during pregnancy increases the risk of sudden infant death syndrome (SIDS) in offspring, we conducted a population-based case-control study using the California linked birth and death certificate data. All infants who died of SIDS (ICD-9 code 798.0) during 1989-91 were identified as cases. More than 96% of the identified SIDS cases were diagnosed through autopsy. Ten controls who did not die from SIDS were randomly selected for each case from the birth certificate matched to the case on the year of birth. Among 2,029 cases and 21,037 controls included in the final analysis, mothers of 49 cases (2.4%) and 406 controls (1.9%) had a diagnosis of either pre-eclampsia or eclampsia noted on the birth certificate. After adjustment for maternal age, prenatal smoking, race/ethnicity, parity, maternal education, gestational age at the initial visit for prenatal care, infant year of birth and infant sex, maternal pre-eclampsia/ eclampsia during pregnancy was associated with a 50% increased risk of SIDS in the offspring (odds ratio = 1.5, 95% confidence interval 1.1, 2.0). Potential under-reporting of pre-eclampsia/eclampsia on the birth certificates was likely to be non-differential and is unlikely to explain the finding. Fetal hypoxia resulting from pre-eclampsia/ eclampsia or immunological aetiology affecting the risk of both pre-eclampsia/eclampsia and SIDS may explain the finding.

Changing paternity and the risk of preeclampsia/eclampsia in the subsequent pregnancy

To determine whether changing paternity affects the risk of preeclampsia or eclampsia in the subsequent pregnancy and whether the effect depends on a woman's history of preeclampsia/eclampsia with her previous partner, a cohort study was conducted based on 140,147 women with two consecutive births during 1989-1991 identified through linking of annual California birth certificate data. Among women without preeclampsia/eclampsia in the first birth, changing partners resulted in a 30% increase in the risk of preeclampsia/eclampsia in the subsequent pregnancy compared with those who did not change partners (95% confidence interval: 1.1, 1.6). On the other hand, among women with preeclampsia/eclampsia in the first birth, changing partners resulted in a 30% reduction in the risk of preeclampsia/eclampsia in the subsequent pregnancy (95% confidence interval: 0.4, 1.2). The difference of the effect of changing paternity on the risk of preeclampsia/eclampsia between women with and those without a history of this condition was significant (p < 0.05 for the interaction term). The above estimates were adjusted for potential confounders. These findings suggest that the effect of changing paternity depends on the history of preeclampsia/eclampsia with the previous partner and support the hypothesis that parental human leukocyte antigen sharing may play a role in the etiology of preeclampsia/eclampsia.

Maternal placental abnormality and the risk of sudden infant death syndrome

To determine whether placental abnormality (placental abruption or placental previa) during pregnancy predisposes an infant to a high risk of sudden infant death syndrome (SIDS), the authors conducted a population-based case-control study using 1989-1991 California linked birth and death certificate data. They identified 2,107 SIDS cases, 96% of whom were diagnosed through autopsy. Ten controls were randomly selected for each case from the same linked birth-death certificate data, matched to the case on year of birth. About 1.4% of mothers of cases and 0.7% of mothers of controls had either placental abruption or placenta previa during the index pregnancy. After adjustment for potential confounders, placental abnormality during pregnancy was associated with a twofold increase in the risk of SIDS in offspring (odds ratio = 2.1, 95% confidence interval 1.3-3.1). The individual effects of placental abruption and placenta previa on the risk of SIDS did not differ significantly. An impaired fetal development due to placental abnormality may predispose an infant to a high risk of SIDS.

Transient neurologic symptoms after spinal anesthesia: an epidemiologic study of 1,863 patients

BACKGROUND

Recent evidence suggests that transient neurologic symptoms commonly follow lidocaine spinal anesthesia. However, information concerning factors that affect their occurrence is limited. Accordingly, to evaluate many potential risk factors, the authors undertook a prospective, multicenter, epidemiologic study.

METHODS

On a voluntary basis, anesthetists at 15 participating centers forwarded a data sheet on patients who had spinal anesthesia to a research nurse blinded to the details of anesthesia and surgery. A subset was randomly selected for follow-up. The pressure [corrected] of transient neurologic symptoms, defined as leg or buttock pain, was the principal outcome variable. Logistic regression was used to control for potential confounders, and adjusted odds ratios and confidence intervals were used to estimate relative risk.

RESULTS

During a 14-month period, 1,863 patients were studied, of whom 47% received lidocaine, 40% bupivacaine, and 13% tetracaine. Patients given lidocaine were at higher risk for symptoms compared with those receiving bupivacaine (relative risk, 5.1; 95% CI, 2.5 to 10.2) or tetracaine (relative risk, 3.2; 95% CI, 1.04 to 9.84). For patients who received lidocaine, the relative risk of transient neurologic symptoms was 2.6 (95% CI, 1.5 to 4.5) with the lithotomy position compared with other positions, 3.6 (95% CI, 1.9 to 6.8), for outpatients compared with inpatients, and 1.6 (95% CI, 1 to 2.5) for obese (body mass index >30) compared with nonobese patients.

CONCLUSIONS

These results indicate that transient neurologic symptoms commonly follow lidocaine spinal anesthesia but are relatively uncommon with bupivacaine or tetracaine. The data identify lithotomy position and outpatient status as important risk factors in patients who receive lidocaine. Among other factors postulated to increase risk, obesity had an effect of borderline statistical significance, whereas age, sex, history of back pain, needle type, and lidocaine dose and concentration failed to affect risk.

Predictions of protein secondary structures using factor analysis on Fourier transform infrared spectra: effect of Fourier self-deconvolution of the amide I and amide II bands

Fourier self-deconvolution (FSD) was performed on protein amide I and II Fourier transform infrared (FTIR) spectra to test if the resultant increased band shape variation would lead to improvements in protein secondary structure prediction with our factor analysis based restricted multiple regression (RMR) methods. FTIR spectra of 23 proteins dissolved in H2O were measured and normalized to a constant amide I peak absorbance. The deconvolved spectra were renormalized by area so that the deconvolved spectra sets had the same area as before. Principal component analysis of the deconvolved spectra sets was carried out, which was followed by a selective multiple linear regression (RMR) analysis of the principal component loadings with regard to the fractional components (FC) of secondary structure. As compared to analyses based on the original spectra set, helix and sheet predictions were not noticeably improved by FSD; but, if a very large number of component spectra (16) were retained in the pool to select which loadings to be used in the RMR optimization, better predictions of turn and "other" resulted. The prediction quality varied depending on the deconvolution parameters used.

Cystic fibrosis heterozygote screening in 5,161 pregnant women

A screening program for cystic fibrosis (CF) heterozygotes was conducted in a large HMO prenatal population, to evaluate the level of interest among eligible patients, the effectiveness of prescreening education, attitudes toward the screening process, psychological effects, and utilization of prenatal diagnosis and its outcomes. The heterozygote identification rate and frequency of specific CFTR mutations were also assessed. Identified carriers were offered genetic counseling and testing of male partners. Prenatal diagnosis was offered if both parents were identified as carriers. A total of 5,161 women underwent carrier testing; 947 others completed survey instruments only. The acceptance rate of screening was high (78%), and pretest education by videotape was generally effective. Adverse psychological effects were not reported. Participants generally found screening to be desirable and useful. Screening identified 142 female heterozygotes, 109 couples in which the male partner was not a carrier, and 7 high-risk couples. The incidence of R117H mutations was much higher than expected. The number of identified carriers was much lower in Hispanics than in Caucasians. We conclude that large-scale prenatal screening for CF heterozygotes in the absence of a family history of CF is an acceptable method for identifying couples at risk for affected fetuses. Sufficient pretest education can be accomplished efficiently, test insensitivity is well accepted, adverse psychological events are not observed, and general patient satisfaction is high.

Mortality following conjugal bereavement and the effects of a shared environment

The effect of bereavement on mortality among surviving spouses was examined in a cohort of 12,522 spouse pairs belonging to a prepaid health care plan in northern California. Both spouses were examined and completed a questionnaire between 1964 and 1973, and they were followed for mortality through 1987. Between 1964 and 1987, 1,453 men (12%) and 3,294 women (26%) were bereaved; 440 bereaved men (30%) and 510 women (15%) died during follow-up. Mortality following bereavement was significantly elevated in both men and women after adjusting for age, education, and other predictors of mortality in proportional hazards analyses. The highest relative risks (RRs) of mortality occurred 7-12 months following bereavement. Among women, the RR was 1.9 (95% confidence interval (CI) 1.35-2.71) 7-12 months after bereavement. Among men, the effect of bereavement interacted with prior health status as follows: In men with few health problems, the RR of mortality was 2.12 (95% CI 1.42-3.17); men with many health problems had a RR of 1.56 (95% CI 0.98-2.55) 7-12 months after bereavement. In both men and women, the RR declined after the first year of bereavement but remained above 1.0 for more than 2 years after bereavement. The addition of terms reflecting the influence of the other spouse's characteristics and behaviors did not alter the RR of mortality, indicating no effect of a shared unfavorable environment on mortality following bereavement.