Chemical and physical properties of radionuclides

There are many radionuclides with a wide range of energies and half-lives available for use as non-sealed radiotherapeutic agents. To date, no single radionuclide has emerged as being clearly superior to all others, in the way that ^99mTc predominates in diagnostic imaging. It is unlikely that one will emerge. Instead, if a particular application demands certain decay properties, the radionuclide which will be used will be the one for which appropriate chemistry can be developed and which can be produced and distributed most economically.     

Probabilistic computation by neuromine networks

In this paper, we address the question, can biologically feasible neural nets compute more than can be computed by deterministic polynomial time algorithms? Since we want to maintain a claim of plausibility and reasonableness we restrict ourselves to algorithmically easy to construct nets and we rule out infinite precision in parameters and in any analog parts of the computation. Our approach is to consider the recent advances in randomized algorithms and see if such randomized computations can be described by neural nets. We start with a pair of neurons and show that by connecting them with reciprocal inhibition and some tonic input, then the steady-state will be one neuron ON and one neuron OFF, but which neuron will be ON and which neuron will be OFF will be chosen at random (perhaps, it would be better to say that microscopic noise in the analog computation will be turned into a megascale random bit). We then show that we can build a small network that uses this random bit process to generate repeatedly random bits. This random bit generator can then be connected with a neural net representing the deterministic part of randomized algorithm. We, therefore, demonstrate that these neural nets can carry out probabilistic computation and thus be less limited than classical neural nets.     

简述疫苗安全性管理

疫苗接种是保护公众健康最有效的措施之一,疫苗可有效降低传染病的发病率和死亡率。与疫苗的有效性评估不同,疫苗的安全性不能直接测定,只能通过有限的疫苗不良事件的相关情况来推断。对疫苗安全性监测的科学理论,全球关注的个案研究,以及注册前有关疫苗的临床试验安全性的相关事宜进行了简介。     

Effect of melatonin administration on DNA damage and repair responses in lymphocytes of rats subchronically exposed to lead

In humans, autosomal dominant or X-linked disease can arise through a phenomenon termed haploinsufficiency, where one remaining wild-type allele is insufficient for function. In model organisms, the impact of heterozygosity can be tested directly with engineered mutant alleles or in a hemizygous state where the expression of one allele is abrogated completely. This review will focus on haploinsufficiency as it relates to telomerase and telomere length maintenance and, citing selected examples in various model organisms, it will discuss how the problem of gene dosage relates to telomere function in normal and diseased states.     

Gene identification by shotgun antisense.

Shotgun antisense is a technique to make a random set of mutant cells or organisms in such a way that one can select an interesting mutant and then sequence part of the mutated gene within a day. In addition to the fantastic rapidity with which one can identify the mutated gene, there are more advantages of this technique over other mutagenesis techniques: (1) one can identify genes that when completely repressed are lethal; (2) one can select which sets of genes will be mutated; and (3) genes that are expressed from multiple copies can be repressed and thus identified.     

Study of the validity of channeling for hrem diffraction

The computation of many beam dynamical electron diffraction can be done numerically using rather sophisticated computer programs so that the physical insight is often lost. It will be shown that, in a crystal in zone oriëntation, the electrons are trapped in the atom columns which then acts as channels. In this way a one to one correspondence between the electron wavefunction and the structure of the object is maintained. This channeling approach enables to describe the diffraction in a much simpler way: the wavefunction is expanded in eigenfunctions of the Hamiltonian. For most kind of columns in a zone axis oriëntation only one bound state will occur which leads to a perfectly oscillatory motion of the electron in the column which can be expressed in a very simple form. The validity is confirmed by comparison with complete dynamical calculations.     

Unconventional bed mates: Gaia and the selfish gene

In this forum, David M. Wilkinson argued that Gaia-type phenomena can be explained by conventional ecological ideas meaning that such phenomena do not require major changes to existing ecological or evolutionary theory. Overstating my case a little, I will argue that a reconciliation between Gaia and Darwinism will not be conventional in the sense of mainstream ecology. The main addition of this essay is an exploration in how far the claim that the atmosphere is an extension of life on Earth is logically correct. In a thought experiment, the idea of extended phenotypes by Richard Dawkins can be integrated with the one of Gaia. The problem of cheats remains pertinent, however, because the atmosphere will not select differentially between cheats and non-cheats. Conclusion: Gaia-type phenomena will be by-products of naturally selected traits. As such they are not jeopardised by cheats, because side effects can be free to self-organise, while the main effects will be naturally selected for evolutionarily stable states. Understanding the laws of self-organisation of such side effects will be of major importance to all environmental sciences.     

一类具有阶段结构的病毒动力学模型

在病毒能影响未感染细胞的产生的假设下,本文考虑了一类被感染细胞具有潜伏和活性两阶段的动力学模型,通过对模型进行近似和简化,得到了病毒的基本再生率．当基本再生率小于1时病毒将最终灭绝;当基本再生率大于1时,模型存在唯一的正平衡点,它是局部渐近稳定的,并且病毒持续存在．     

On cotransmission & neurotransmitter phenotype plasticity

Most neurons in the nervous system appear to contain and release more than one chemical acting as a neurotransmitter or neuromodulator. Cotransmission can therefore be considered the rule rather than the exception. Indeed, cotransmission of a classical neurotransmitter and a peptide is a ubiquitous phenomenon, but several neuron types can also contain more than one classical neurotransmitter [glutamate, gamma-amino butyric acid (GABA), acetylcholine, dopamine, etc.]. Although the expression of peptide cotransmitters is known to be highly regulated in response to various physiological, chemical and pathological signals, new data now suggest that a similar situation prevails in neurons that co-release two classical transmitters. In this review we will consider a number of recently described examples of cotransmission implicating more than one classical neurotransmitter. We will also consider new data showing that during development and later in adulthood, as well as in the context of disease, the neurotransmitter phenotype of neurons can be highly plastic as revealed by changes in the expression of neurotransmitter synthesis enzymes and vesicular neurotransmitter transporters.     

Lactic acid bacteria and proteomics: current knowledge and perspectives

Lactic acid bacteria (LAB) are widely used in the agro-food industry. Some of the LAB also participate in the natural flora in humans and animals. We review here proteomic studies concerning LAB. Two methods of research can be distinguished. In the first one, a systematic mapping of proteins is attempted, which will be useful for taxonomy and to function assignment of proteins. The second one focuses particularly on proteins whose synthesis is induced by various environmental situations or stresses. However, both approaches are complementary and will give new insights for the use of bacteria in industry, in human health and in the struggle against bacterial pathogens. Interest in LAB is growing, showing thus an increasing concern of their rational use and one can foresee in the near future an increasing use of proteomics as well as genomics.     

« Flûte » et pointes de la Grosse Badlhöhle, Autriche

The Grosse Badlhöhle (Austria, Steiermark) is the origin of one of the most perfect bone points of the early Aurignacian and one of the best perforated femurs of the same period, which can be regarded as musical instruments. Two other fragments of points raise intriguing questions on the first Homo sapiens sapiens which cannot be solved today but will contribute to future research. A review on the debate of Palaeolithic flutes will follow with experimental proofs of boring artificial holes with high quality pictures on the blow-hole and the lack of gnawing traces on the opposite face. The musical possibility of an instrument with only one hole is discussed with ethnographic analogies. Hafting, optimal conditions of strength and possible use of arrows will close the discussion on the Badlhöhle bone artefacts.     

The future of clinical engineering: technology that enables improved patient care

Speakers at this year's ACCE Symposium will describe in detail the scope and depth of technological and other factors that are at work changing the healthcare delivery paradigm. Other presenters will explore the impact the changes will likely have on the clinical engineering profession. Still others will outline the steps necessary for clinical engineers to take to effectively prepare for the challenges facing them. The experts agree: clinical engineering is at a critical crossroads. No one who intends to pursue clinical engineering or healthcare technology management over the next 10 years can afford to miss this year's meeting.     

创新型单手操作新生儿复苏器的研制

该复苏器操作简便、安全。只要把面罩盖住新生儿口鼻,用一只手即可对手泵吸球进行加压给氧。加压过高时能排余气并发声报警,避免发生气胸,提高抢救效果。另外,该手泵吸球可一物两用,按瘪后将长嘴放人新生儿口内或鼻孔口,放松时可吸羊水等黏液。节约原材料,降低成本,大有利于新生儿窒息复苏的推广普及。     

The inbred mouse in pigmentation research: significance of a congenic developmental system

Pigment mutations in inbred mice have been important to many new scientific developments over the past century. Inbred mice are essentially genetically alike because of 10-20 generations or more of sibling mating or the equivalent. Mice of the same inbred strain that differ at only one locus can be used to evaluate the phenotypic effects of that one locus without complication of variation at other loci. Similarly, genic interactions among the functions of two or more loci are evaluated by comparing them in all combinations against a uniform genetic background. The next logical step in describing the pigment system will occur when all pigment cell biologists who use mice (cells, tissues, DNA, RNA) make certain that their mice are congenic with C57BL/6J. As a result, the work of all investigators will be genetically comparable. Their work will also be comparable to those investigating other organ systems, because NIH has chosen C57BL/6J as one of its two standard strains. As a result of this standardization, interactions among the different gene loci that function in the pigment system will become more readily evident and the community of pigment cell biologists using congenic mice will be able to analyze the functional interplay of loci that regulate the entire pigment system in the same way that earlier researchers analyzed one mutant allele, or the interactions of two mutant loci.     

The Inbred Mouse in Pigmentation Research:

Pigment mutations in inbred mice have been important to many new scientific developments over the past century. Inbred mice are essentially genetically alike because of 10–20 generations or more of sibling mating or the equivalent. Mice of the same inbred strain that differ at only one locus can be used to evaluate the phenotypic effects of that one locus without complication of variation at other loci. Similarly, genic interactions among the functions of two or more loci are evaluated by comparing them in all combinations against a uniform genetic background. The next logical step in describing the pigment system will occur when all pigment cell biologists who use mice (cells, tissues, DNA, RNA) make certain that their mice are congenic with C57BL/6J. As a result, the work of all investigators will be genetically comparable. Their work will also be comparable to those investigating other organ systems, because NIH has chosen C57BL/6J as one of its two standard strains. As a result of this standardization, interactions among the different gene loci that function in the pigment system will become more readily evident and the community of pigment cell biologists using congenic mice will be able to analyze the functional interplay of loci that regulate the entire pigment system in the same way that earlier researchers analyzed one mutant allele, or the interactions of two mutant loci.     

A two-locus mutation—Selection model and some of its evolutionary implications

The deterministic properties of a two-locus model with mutation and selection have been investigated. The mutation process is unidirectional, and the model is so constructed that the genetic variation at one locus is selectively neutral in the absence of a mutant allele at the other locus. All genotypes with three or four mutant alleles are deleterious, while the double heterozygotes may have the same fitness as the standard genotype. If one of the mutant alleles becomes fixed in the population, then the other locus will show a regular one-locus mutation-selection balance. Such a boundary equilibrium may be unstable or stable in the full two-locus setting. In the symmetric case, which is analyzed in details, the population will either go to one of the two boundary equilibria, or to a fully polymorphic equilibrium at which both the mutant alleles are rare. The origin of reproductive separation between two populations via the fixation of complementary deleterious mutants at different loci, and the fixation of nonfunctional alleles at duplicated loci, are two biological processes which both can be studied with the present model. In the last part of the paper we show how the results from the deterministic analysis can be used to predict how different factors will influence the rates of evolution in these systems.     

Stabilizing Effect of Cannibalism in a Two Stages Population Model

In this paper we build a prey–predator model with discrete weight structure for the predator. This model will conserve the number of individuals and the biomass and both growth and reproduction of the predator will depend on the food ingested. Moreover the model allows cannibalism which means that the predator can eat the prey but also other predators. We will focus on a simple version with two weight classes or stage (larvae and adults) and present some general mathematical results. In the last part, we will assume that the dynamics of the prey is fast compared to the predator’s one to go further in the results and eventually conclude that under some conditions, cannibalism can stabilize the system: more precisely, an unstable equilibrium without cannibalism will become almost globally stable with some cannibalism. Some numerical simulations are done to illustrate this result.     

Causal Drift,Robust Signaling,and Complex Disease

The phenotype of many regulatory circuits in which mutations can cause complex, polygenic diseases is to some extent robust to DNA mutations that affect circuit components. Here I demonstrate how such mutational robustness can prevent the discovery of genetic disease determinants. To make my case, I use a mathematical model of the insulin signaling pathway implicated in type 2 diabetes, whose signaling output is governed by 15 genetically determined parameters. Using multiple complementary measures of a parameter’s importance for this phenotype, I show that any one disease determinant that is crucial in one genetic background will be virtually irrelevant in other backgrounds. In an evolving population that drifts through the parameter space of this or other robust circuits through DNA mutations, the genetic changes that can cause disease will vary randomly over time. I call this phenomenon causal drift. It means that mutations causing disease in one (human or non-human) population may have no effect in another population, and vice versa. Causal drift casts doubt on our ability to infer the molecular mechanisms of complex diseases from non-human model organisms.     

Creating new restriction sites by silent changes in coding sequences

We present methods for identifying a useful type of DNA site--one that can be mutated to create a new restriction site within a coding region without changing the amino acid sequence. These "latent sites" are abundant--silent mutations creating one of 44 different 6-bp or 8-bp recognition sites were found at relatively high density, roughly one latent site per 9 bp, in the eleven genes tested. Our analysis suggests that site-directed mutagenesis can be used to refashion coding sequences at will for flexible analysis.