Experimental intravitreal gentamicin

Rabbits received intravitreal injections of gentamicin and indirect ophthalmoscopy, electroretinography, and histopathology determined relative toxicity. An intravitreal dose of 0.1 to 0.2 mg of commercially available gentamicin was well tolerated in the rabbit eye. A dosage of 0.4 mg or higher consistently produced significant ocular toxicity as evidenced by extinction of the electroretinogram, gross fundus changes, and histopathologic alterations.     

Elastic image mapping for 4-D dose estimation in thoracic radiotherapy

PURPOSE: Demonstrate the path integration of a four-dimensional (4-D) dose distribution onto the 3-D anatomy. MATERIALS AND METHODS: A computer-generated 4-D thoracic phantom with a lung tumour was constructed. Eight respiratory phases were generated. A radiotherapy treatment plan was applied to all the phases resulting in a 4-D dose distribution. An elastic image registration algorithm was used to find the vector displacement between all the image elements and the end expiration phase. The path-integrated tissue dose distribution and each component dose distribution were compared with the planned dose distribution. RESULTS: Numerical path integration was performed to calculate the tissue dose distribution. Loss of tumour coverage was the predominant effect observed with tumour motion in this study. The loss was asymmetric and dependent on the tumour trajectory. CONCLUSION: The elastic image registration allowed an accurate path integration through a 4-D data set to produce an accurate 3-D tissue dose estimate.     

The effect of potassium on translocation of photosynthates and yield pattern of potato plants

The effect of increasing potassium supplies on the translocation of ¹⁴C-labelled photosynthates from the leaves to the tubers was investigated in potatoes at different growth stages. Until flowering most of the assimilates were used for the development of above-ground parts. With adequate K nutrition two thirds of the labelled photosynthates passed within one day into the tubers when after flowering intensive growth of tubers set in. With insufficient K supply (0.4 mequiv. K/litre), however, only half of the photosynthates were translocated to the tubers during the same period. The heavier accumulation of assimilates in the leaves resulted in a lower rate of photosynthesis in relation to leaf matter. It could thus be confirmed that potassium directly favours the transport of assimilates and, due to the faster translocation of photosynthates, brings about a higher assimilation rate of the leaves. The plants of the K₃ treatment (10 mequiv. K/litre) at all growth stages produced the highest tuber yield per leaf matter. On the other hand, the amount of leaf matter in these plants was smaller, so that the plants supplied with medium K rates (2.0 mequiv. K/litre) gave the highest absolute tuber yield. Within 24 hours three quarters of the labelled photosynthates were converted, for the major part into starch and protein. Potassium favoured in the young above-ground parts the conversion of photosynthates to protein and in the tubers the synthesis of starch. Its effect on metabolism therefore differs in dependence on plant organ and physiological age of the plant.     

Effect of artificial perspiration and cleaning chemicals on the mechanical and chemical properties of ballistic materials

During routine field use of soft body armor, the ballistic panels become saturated with perspiration. This condition motivates the user to clean and/or deodorize the armor, and anecdotal evidence is given for various methods used to accomplish this. Although the cleaning/deodorization is usually performed on the armor liners and coverings, there is concern that the chemicals could seep into the ballistic panels and damage the fibers. The purpose of this study was to assess the effect of artificial perspiration and cleaning chemicals on the mechanical and chemical properties of aramid, poly(p‐phenylene benzobisoxazole), and ultrahigh‐molecular‐weight polyethylene yarns after controlled cycles of exposure to artificial perspiration and dilute solutions of common cleaning chemicals. It was observed that the effect of the artificial perspiration on the properties of all of the materials tested was the same as that of water alone. Of all of the cleaning chemicals used, only chlorine bleach had a detrimental effect on the yarn properties. All other cleaning chemicals had the same effect as water alone. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Performance Analysis of Covariance Matrix Estimates in Impulsive Noise

This paper deals with covariance matrix estimates in impulsive noise environments. Physical models based on compound noise modeling [spherically invariant random vectors (SIRV), compound Gaussian processes] allow to correctly describe reality (e.g., range power variations or clutter transitions areas in radar problems). However, these models depend on several unknown parameters (covariance matrix, statistical distribution of the texture, disturbance parameters) that have to be estimated. Based on these noise models, this paper presents a complete analysis of the main covariance matrix estimates used in the literature. Four estimates are studied: the well-known sample covariance matrix M_SCM and a normalized version M_N, the fixed-point (FP) estimate M_FP, and a theoretical benchmark M_TFP. Among these estimates, the only one of practical interest in impulsive noise is the FP. The three others, which could be used in a Gaussian context, are, in this paper, only of academic interest, i.e., for comparison with the FP. A statistical study of these estimates is performed through bias analysis, consistency, and asymptotic distribution. This study allows to compare the performance of the estimates and to establish simple relationships between them. Finally, theoretical results are emphasized by several simulations corresponding to real situations.     

Mitochondrial footprints of human expansions in Africa

mtDNA studies support an African origin for modern Eurasians, but expansion events within Africa have not previously been investigated. We have therefore analyzed 407 mtDNA control-region sequences from 13 African ethnic groups. A number of sequences (13%) were highly divergent and coalesced on the "mitochondrial Eve" in Africans. The remaining sequences also ultimately coalesced on this sequence but fell into four major clusters whose starlike phylogenies testify to demographic expansions. The oldest of these African expansions dates to approximately 60,000-80,000 years ago. Eurasian sequences are derived from essentially one sequence within this ancient cluster, even though a diverse mitochondrial pool was present in Africa at the time.