Solvent effects on the crystal structure of silver pentacyanocyclopentadienide: supramolecular isomerism and solvent coordination.

Several coordination polymers of silver(i)-pentacyanocyclopentadienide (PCC) were studied by X-ray diffraction to examine the effects of different solvents on supramolecular isomerism of the PCC-ligand. While alcohols yield supramolecular isomers of [Ag(PCC)] without coordination of solvent molecules, less polar solvents show coordinate binding. The influence of solvent polarity can be observed by a gradual change in the lattice structure featuring distinct motifs.

Managerial practices regarding workers working while ill.

Surveillance data indicate that handling of food by an ill worker is a cause of almost half of all restaurant-related outbreaks. The U.S. Food and Drug Administration (FDA) Food Code contains recommendations for food service establishments, including restaurants, aimed at reducing the frequency with which food workers work while ill. However, few data exist on the extent to which restaurants have implemented FDA recommendations. The Centers for Disease Control and Prevention's Environmental Health Specialists Network (EHS-Net) conducted a study on the topic of ill food workers in restaurants. We interviewed restaurant managers (n = 426) in nine EHS-Net sites. We found that many restaurant policies concerning ill food workers do not follow FDA recommendations. For example, one-third of the restaurants' policies did not specifically address the circumstances under which ill food workers should be excluded from work (i.e., not be allowed to work). We also found that, in many restaurants, managers are not actively involved in decisions about whether ill food workers should work. Additionally, almost 70% of managers said they had worked while ill; 10% said they had worked while having nausea or "stomach flu," possible symptoms of foodborne illness. When asked why they had worked when ill, a third of the managers said they felt obligated to work or their strong work ethic compelled them to work. Other reasons cited were that the restaurant was understaffed or no one was available to replace them (26%), they felt that their symptoms were mild or not contagious (19%), they had special managerial responsibilities that no one else could fulfill (11%), there was non-food handling work they could do (7%), and they would not get paid if they did not work or the restaurant had no sick leave policy (5%). Data from this study can inform future research and help policy makers target interventions designed to reduce the frequency with which food workers work while ill.

The role of V2 vasopressin antagonists in hyponatremia.

Hyponatremia is a frequent electrolyte disorder. It is often found in congestive cardiac failure, liver cirrhosis, plasma volume contraction and in SiADH. In these disorders hyponatremia is caused by nonosmotic vasopressin and sustained fluid intake. This provides a rationale for V2 vasopressin receptor antagonists in the treatment of hyponatremia. There is now convincing evidence from different animal models of congestive cardiac failure that peptide and non-peptide V2 vasopressin antagonists effectively increase renal water diuresis and plasma sodium concentration. In addition, several of the experimental studies also showed an improvement of hemodynamic changes of cardiac failure in response to V2 antagonists. Data in patients indicated that oral non-peptide V2-antagonists correct hyponatremia and may improve hemodynamic derangements in cardiac failure. In addition, experimental and clinical studies of V2 antagonists have been undertaken in liver cirrhosis and SiADH. In those studies hyponatremia was improved or corrected, too. Taken together, V2 vasopressin antagonists promise to become therapeutic agents in hyponatremic disorders.

Treatment of severe hyponatremia: conventional and novel aspects.

Hyponatremia is a frequent electrolyte disorder. A hyponatremia is called acute severe (<115 mM) when the duration has been <36 to 48 h. Such patients often have advanced symptoms as a result of brain edema. Acute severe hyponatremia is a medical emergency. It should be corrected rapidly to approximately 130 mM to prevent permanent brain damage. In contrast, in chronic severe hyponatremia (>4 to 6 d), there is no brain edema and symptoms are usually mild. In such patients, a number of authors have recommended a correction rate <0.5 mM/h to approximately 130 mM to minimize the risk of cerebral myelinolysis. Sometimes it is not possible to diagnose whether a severe hyponatremia is acute or chronic. In such cases, an initial imaging procedure is helpful in deciding whether rapid or slow correction should be prescribed. The modalities of treatment of severe hyponatremia have so far consisted of infusions of hypertonic saline plus fluid restriction. In the near future, vasopressin antagonists will become available. Preliminary experience has already demonstrated their efficiency of inducing a sustained water diuresis and a correction of hyponatremia.

[Hyponatremia--with comments on hypernatremia]. / Hyponatriämie--mit Anmerkungen zur Hypernatriämie.

Disorders of the serum sodium concentration (hypo- and hypernatremia) are amongst the most frequent electrolyte disorders in clinical medicine. They are attributable to disturbance of to water metabolism. Hyponatremia is almost always a condition of water excess while hypernatremia is due water deficiency. Physiological normonatremia (normal plasma osmolality) is maintained by an integrated system involving regulated water intake via thirst and control of water excretion via antidiuretic hormone secretion. Therefore hypo- and hypernatremia should be analyzed in terms of dysregulated ADH secretion, fluid intake and renal water excretion. Hyponatremia is usually a disorder of vasopressin excess, due to 'non-osmotic' vasopressin release. The latter may occur in two different settings: (I) SIADH, (II) baroreceptor mediated vasopressin secretion (cardiac failure, liver cirrhosis). This entities are easy to distinguish in clinical practice. SIADH is associated with striking lower plasma concentrations of urate, creatinine and urea. In SIADH the blood pressure is normal and there is no edema. In contrast in the hyponatremia of liver cirrhosis and heart failure the plasma measurements indicated are usually slightly elevated, the blood pressure is low and there is edema. The typical patient with hypernatremia is old and has no thirst sensation. Hypo- or hypernatremia may cause major neurologic symptoms. These symptoms are more related to the rate of change in the serum sodium concentration than to the absolute level of a hypo- or hypernatremia reached. The traditional treatment for hyponatremia used to be water restriction. However V2-Vasopressin-Antagonists may provide a better treatment modality in the future. Hypernatremia is treated by slow rehydratation.

The treatment of severe hyponatremia.

Severe hyponatremia may be chronic (days) or acute (hours), symptomatic or asymptomatic. Severe chronic symptomatic hyponatremia (serum sodium concentration < 110 to 115 mM/liter) occurs most commonly in the syndrome of inappropriate antidiuretic hormone secretion (SIADH). The treatment of this hyponatremia is a challenge to practicing physicians, in part because an overly rapid correction of hyponatremia may cause brain damage. The latter sometimes takes the form of central pontine myelinolysis (CPM). On the basis of available clinical and experimental literature, the rate of correction of this symptomatic hyponatremia should be no more than 0.5 mM per liter per hour, and the initial treatment should be halted once a mildly hyponatremic range of the serum sodium concentration has been reached (approximately 125 to 130 mM/liter). In contrast, severe chronic asymptomatic hyponatremia may be treated sufficiently by a fluid restriction. On the other hand, severe symptomatic acute hyponatremia should be treated promptly and rapidly, using hypertonic saline, to initially reach a mildly hyponatremic level.

A method for measuring the presampled MTF of digital radiographic systems using an edge test device.

The modulation transfer function (MTF) of radiographic systems is frequently evaluated by measuring the system's line spread function (LSF) using narrow slits. The slit method requires precise fabrication and alignment of a slit and high radiation exposure. An alternative method for determining the MTF uses a sharp, attenuating edge device. We have constructed an edge device from a 250-microm-thick lead foil laminated between two thin slabs of acrylic. The device is placed near the detector and aligned with the aid of a laser beam and a holder such that a polished edge is parallel to the x-ray beam. A digital image of the edge is processed to obtain the presampled MTF. The image processing includes automated determination of the edge angle, reprojection, sub-binning, smoothing of the edge spread function (ESF), and spectral estimation. This edge method has been compared to the slit method using measurements on standard and high-resolution imaging plates of a digital storage phosphor (DSP) radiography system. The experimental results for both methods agree with a mean MTF difference of 0.008. The edge method provides a convenient measurement of the presampled MTF for digital radiographic systems with good response at low frequencies.

Human vertebral body apparent and hard tissue stiffness.

Cancellous bone apparent stiffness and strength are dependent upon material properties at the tissue level and trabecular architecture. Microstructurally accurate, large-scale finite element (LS-FE) models were used to predict the experimental apparent stiffness of human vertebral cancellous bone and to estimate the trabecular hard tissue stiffness. Twenty-eight LS-FE models of cylindrical human vertebral cancellous bone specimens (8 mm in diameter, 9.5 mm in height, one each from twenty-eight individuals) were generated directly from microcomputed tomography images and solved by a special purpose iterative finite element program. The experimental apparent stiffness and strength of the specimens were determined by mechanical testing to failure in the infero superior direction. Morphometric measurements including bone volume fraction (BV/TV), three eigenvalues of the fabric tensor and average P(L) were also calculated. The finite element estimate of apparent stiffness explained much of the variance in both experimental apparent stiffness (r2=0.89) and experimental apparent strength (r2=0.87). Stepwise linear regression analysis demonstrated that the LS-FE estimated apparent stiffness was the only significant predictor of experimental apparent stiffness and strength when it was included with all measured morphometric values. Hard tissue stiffness was quite variable between individuals (mean, 5.7 GPa; S.D. 1.6 GPa), but was not significantly related to age, sex, race, weight or morphometric measures for this sample.

A cone beam computed tomography system for true 3D imaging of specimens.

A system for 3D cone beam computed tomography has been developed, consisting of a microfocus x-ray source and x-ray image intensifier coupled to a CCD camera. Full width at half maximum resolving power has been experimentally measured to be 70 microns when imaging 10 mm diameter objects. The 3D nature of the resulting image data can be used to visualize internal structure and compute parameters such as volume, surface area, and surface/volume orientation.

[Sudden hyponatremia with unconsciousness. Case report and brief overview of the syndrome of inadequate antidiuresis (SIAD or Schwartz-Bartter syndrome]. / Eine plötzliche Hyponatriämie mit Bewusstlosigkeit. Fallbeschreibung und kurze Ubersicht über das Syndrom der Inadäquaten Antidiurese (SIAD oder Schwartz-Bartter-Syndrom).

A sixty-six year old female was admitted to the hospital with an incomplete hemiparesis on the left side combined with a short episode of unconsciousness. According to her husband's account she had a seizure. Relevant laboratory measurements: plasma sodium concentration 113.9 mmol/l, plasma concentration of ADH 10.3 pg/ml, urine sodium concentration 44.4 mmol/l. The plasma concentrations of creatinine and urea were within normal limits. The working hypothesis was SIAD (syndrome of inappropriate antidiuresis) or Schwartz-Bartter-syndrome. The patient was treated immediately with water restriction (500-1000 ml/day), furosemide and i.v. replacement of urinary sodium losses by 3% NaCl. The analysis of cerebrospinal fluid showed pleocytosis and increased concentrations of immunoglobulins G and M. Serological diagnosis was positive for antigen of varicella-zoster virus. These observations were thought to be compatible with a diagnosis of SIAD in the setting of encephalitis. Under water restriction, infusion of 3% saline, treatment with loop diuretics and aciclovir (3 x 750 mg daily) the neurological function returned to normal within 2 days. A standard oral water load on the 14th hospital days showed a return to a normal water metabolism.

Vergence eye movement control and multivalent perception of autostereograms.

We introduce a dynamical model for automatic vergence eye movement control. In connection with our dynamical system of binocular model neurons that solves the correspondence problem of stereo-vision, we present a complete model for stereo-vision. Our automatic vergence eye movement control adjusts an image segment, which is of momentary interest to the observer. The adjustment is done in such a way that we only need to define a disparity search range of minimal extension. Recently, a new method of encoding (3D) three-dimensional information in 2D pictures was designed in the form of computer-generated patterns of colored dots. At first glimpse, these so-called autostereograms appear as structured but meaningless patterns. After a certain period of observation, a 3D pattern emerges suddenly in an impressive way. Applying our algorithm to autostereograms, we find a fully satisfactory agreement with the multivalent perception experienced by humans. As in nature, in our model the phase transition between the initial state and the 3D perception state takes place in a very short time. Our algorithm is very robust against noise, and there is no need to interpolate a sparse depth map.

Giant axonal neuropathy: a generalized disorder of intermediate filaments with longitudinal grooves in the hair.

Giant axonal neuropathy (GAN) is a generalized neurological disorder with accumulation of intermediate filaments in different cell populations. The hallmark are enormous axonal swellings containing densely packed neurofilaments. Clinical symptoms reported so far are mainly limited to the nervous system. We report on a four-year-old girl with clinical and sural nerve biopsy findings typical of GAN. In addition, scanning electron microscopy (SEM) showed longitudinal grooves in the hairs of our patient. This peculiarity so far has only been described in two other patients with GAN. Scanning electron microscopy of hairs therefore may serve as a method of screening in patients suspected of suffering from GAN.

Stereo vision by self-organization.

We propose a new algorithm for stereoscopic depth perception, where the depth map is the momentary state of a dynamic process. To each image point we assign a set of possible disparity values. In a dynamic process with competition and cooperation, the correct disparity value is selected for each image point. Therefore, we solve the correspondence problem by a dynamic, self-organizing process, the structure of which shows analogies to the human visual system. The algorithm can be implemented in a massive parallel manner and yields good results for either artificial or natural images.

Internal exposure to organic substances in a municipal waste incinerator.

Fifty-three persons occupied in a municipal waste incinerator were examined with respect to their internal exposure to organic substances which may be produced during pyrolysis of organic matter. For this purpose the levels of benzene in blood, polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) in plasma, and mono- (MCPs), di- (DCPs), tri- (TCPs), tetra- (TCEPs) and pentachlorophenol (PCP) and hydroxypyrene in urine were determined. For control purposes, 431 men and women were examined. Significantly higher values for the workers were found for the excretion of hydroxypyrene [median (m): 0.24 vs 0.11 microgram/l; non-smokers], 2,4/2,5-DCP (m: 10.5 vs 3.9 micrograms/l) and 2,4,5-TCP (m: 1.2 vs 0.8 micrograms/l) and for the HCB level in plasma (m: 4.4 vs 2.8 micrograms/l). For the concentrations of 4-MCP and 2,3,4,6/2,3,5,6-TECP, the controls had significantly higher concentrations in urine than did the workers in the incineration plant (m: 4-MCP 1.7 vs 1.2; 2,3,4,6/2,3,5,6-TECP: 1.2 vs 0.3 micrograms/l). No significant differences between workers and controls were detected with respect to benzene in blood (m: 0.20 vs 0.28 microgram/l; non-smokers), 2,4,6-TCP and PCPs in urine (m: 0.85 vs 0.60 and 2.2 vs 2.2 micrograms/l) or the levels of PCB congeners in plasma (m: sigma 138, 153, 180: 5.6 vs 4.1 micrograms/l). The elevated levels of hydroxypyrene, 2,4/2,5-DCP, 2,4,5-TCP and HCB in biological material may be related to the incineration of the waste. These elevations, however, are very small and are of interest more from the environmental than from the occupational point of view.

Eigenimage filtering in MR imaging: an application in the abnormal chest wall.

A postprocessing linear filter was applied to spin-echo images on 10 patients with known or suspected chest wall invasion due to bronchogenic carcinoma. This technique known as eigenimage filtering allows selective feature extraction of suspected abnormalities from conventional MR images. The final result is an image with marked increased contrast range through enhancement of a desired process (tumor) with suppression of an interfering process (e.g., normal surrounding tissue). This preliminary work demonstrates the ease with which the technique may be implemented, the contrast enhancement obtained between the desired and the interfering feature in the final eigenimage, and its ability to correct for partial volume averaging effects. Also demonstrated are artifacts that can interfere with the interpretation of the eigenimage and a method for minimizing these artifacts in the final eigenimage.

Eigenimage filtering in MR imaging.

This article presents the technical aspects of a linear filter, referred to as eigenimage filtering, and its applications in magnetic resonance (MR) imaging. The technique is used to obtain a single composite image depicting a particular feature of interest while suppressing one or more interfering features. The appropriate weighting components to be used in the linear filter are determined on the criterion that the desired feature is enhanced while the interfering features are suppressed. The criterion is expressed mathematically as a ratio. By applying Rayleigh's principle, the ratio is maximized by finding the eigenvector associated with the maximum eigenvalue of the corresponding generalized eigenvalue problem. The appropriate weighting factors for the linear filter are the elements of the eigenvector which maximize the ratio. The utilization of the technique is demonstrated in its application to a simulated MR image sequence as well as to acquired MR image sequences of a normal and an abnormal brain.