Forecasting a 2-methylisoborneol outbreak in a brackish lake.

2-Methylisoborneol (2-MIB) is the primary cause of the earthy and musty odor produced by cyanobacteria, which deteriorates the quality of fishery products and tap water. Despite the need for controlling outbreaks, few studies have been conducted on 2-MIB in brackish lakes, where capture fisheries are active. This study examined the association between water quality and the outbreak of 2-MIB in a brackish lake using statistical analysis of long-term monitoring data and developed forecasting models for 2-MIB outbreaks. We investigated Lake Ogawara, which is a brackish lake with a cool-temperate climate in Japan, where 2-MIB outbreaks frequently occur between August and December. Logistic regression analyses were performed using the outbreak or non-outbreak of 2-MIB (2-MIB(+ / -)) as the dependent variable and water quality parameters as the independent variables. The results suggested that the density of 2-MIB-producing cyanobacteria was higher when (1) dissolved inorganic nitrogen concentrations were low under the relaxation of phosphorus limitation and/or (2) salinity or micronutrient concentrations were high. In addition, we successfully developed forecasting models with a high predictive power that determined 2-MIB(+ / -) in August-December using only two water quality parameters: dissolved inorganic phosphate and pH in April and total nitrogen/total phosphorous and salinity in May.

Scan parameters and the diffusion emphasis effect in diffusion-weighted imaging using a motion-probing gradient preparation pulse.

Diffusion-sensitized driven equilibrium preparation (DSDE) is a gradient echo (GRE) diffusion-weighted imaging (DWI) sequence that employs a motion-probing gradient (MPG) preparation pulse and phase cycling. In DSDE, several scan parameters of the MPG preparation pulse and the GRE sequence affect diffusion sensitivity. Our investigation of the relationship between these scan parameters and the diffusion emphasis effect revealed the importance of "prep.TE" in the MPG preparation pulse and "TFE shot interval" in the gradient echo sequence. Appropriate choice of these parameters allows DSDE to provide a similar DWI to that of conventional single-shot SEEPI DWI. We therefore concluded DSDE to be a useful DWI method.

[Survey report on magnetic resonance equipment damage in areas in Miyagi Prefecture affected by the Great East Japan Earthquake].

A questionnaire comprising 14 items, inquiring about the state of damage, whether safety could be ensured, and progress of repair and restoration was distributed to 984 facilities in seven prefectures on the Pacific coast as part of a fact-finding survey of damage caused to magnetic resonance (MR) devices by the Great East Japan Earthquake. In all, 458 responses (46.6%) were collected. In Miyagi Prefecture alone, 65 responses from 105 questionnaires were collected (response rate: 61.9%). The overall incidence of damage was 19.2%, with 57 facilities (12.4%) reporting that displacement of the magnets was the most common problem. The damage event rate in Miyagi Prefecture was 51.3%, with displacement of the magnet being highest at 17 cases (26.2%). There was a high rate of 13 cases (26.5%) of chiller and air conditioning failures and a rapid loss of He in ten MR scanners (20.4%). Notably, 87.8% of facilities in Miyagi Prefecture (24.5% of the total) were affected by earthquakes exceeding 6 on the Japanese Seismic Intensity Scale. Flood damage caused by the tsunami was also seen along the Sanriku coast to Sendai City (six MR scanners, 50% of the total), and was typical of the damage seen in Miyagi Prefecture.

[Influence of imaging parameters on the measurement of apparent diffusion coefficient].

The apparent diffusion coefficient (ADC) values are calculated by using signal intensity in diffusion-weighted images (DWIs) with two or more different b-value. Therefore, the signal to noise ratio (SNR) of DWI with higher b-value may have a big influence on the measured ADC value. We examined the influence of the imaging parameters on the calculated ADC values. The SNR of DWI increased by using a larger voxel size, by means of a decreased number of matrix, an increased slice thickness, and an increased field of view (FOV). However, when the number of excitations was increased to improve the SNR of DWI, the signal intensity of background noise was observed to be slightly increased. It was suggested that the consistency of measured ADC was not preserved when the signal of the DWIs with higher b-value dropped close to the noise level.

Spring to summer nitrogen level in a brackish lake is higher in abundant snowmelt years: Correlation and causation.

Eutrophication is an issue of concern in many brackish lakes with an agricultural watershed. The amount of snowfall in snowy areas is anticipated to decline because of global climate change. The aim of this study was to assess the impact of changes in the inflow of snowmelt on the nutrient concentrations of a downstream brackish lake. In Lake Ogawara, a brackish lake in a snow-covered agricultural area of Japan, we examined the relationships between inflowing river discharge (D/C) during spring and total nitrogen (TN) and total phosphorus (TP) concentrations in the mixolimnion of the lake ([TNmix ] and [TPmix ], respectively) using 29 yr of monitoring data. In addition, we assessed the causal relationship between the D/C and the lake nutrient concentrations. There was large year-to-year variation in D/C during April (D/CApr ), which accounted for 7-31% of the mixolimnion volume. Significant positive correlations were observed between D/CApr and [TNmix ] from the ensuing April to September. On an annual basis, 49% of the interannual variation of the mean [TNmix ] during the ensuing April to September was explained by the interannual variation of D/CApr . Therefore, D/CApr could be useful as a simple index to [TNmix ] in the ensuing spring to summer. It is notable that the relationships between D/CApr and [TNmix ] from April to September was indicated to be acausal by statistical causal inference. Common climate conditions that increase D/CApr (i.e., a cold winter with a high level of precipitation) were found to drive other biogeochemical processes that increased [TNmix ] during the ensuing spring to summer.

[Distortion in diffusion weighted imaging].

The definitional equation of the distortion of echo planar imaging(EPI)was examined. We compared measured values with calculated values by using the definitional equation of the chemical shift of the EPI method that first composed the diffusion-weighted image, and examined the possibility of applying it to the distortion. The results showed that the chemical shift with the definitional equation and the measurement corresponded, and the correlation between the chemical shift and the distortion was acquired. Next, the distortion of each images that composed DWI with the increase and the sign acceptable method difference of b value. The difference in the distortion between each image has increased with the increase in b value. It was assumed that the influence of the eddy currents was due to the high motion probing gradient.