New insights for using self-assembly materials to improve the detection stability in label-free DNA-chip and immuno-sensors

This paper examines reliable advancements in low-cost DNA- and immuno-chips. Capacitance detection was successfully chosen to develop label-free bio-chips. Probe immobilization was rigorously investigated in order to obtain reliable capacitance measurements. Protein probes immobilized by using usual alkanethiols or thiolated ssDNA probes directly immobilized on gold do not allow sufficient stable capacitance measurements. New alkanethiols improved with ethylene–glycol function are shown in this paper to be more suitable materials for capacitive bio-chip development. Atomic Force Microscopy, Quartz Crystal Microbalance, and Capacitance Measurements were used to demonstrate that ethylene–glycol alkanethiols allow high time stability, smaller errors in detection, and improved ideal behaviour of the sensing surfaces. Measured capacitance is in the range of 8–11 nF/mm² for antibody layers and close to 6 nF/mm² for DNA probes. It is in the range of 10–12 nF/mm² and of 4–6 nF/mm² for antigen and DNA detection, respectively. The percentage error in detection is highly improved and it is in the range of 11–37% and of 0,23–0,82% for antigen and DNA, respectively. The reproducibility is also improved and it is close to 0,44% for single spot measurements on ethylene–glycol alkanethiols. A molecular theory attributing these improvements to water molecules strongly coordinated by ethylene–glycol functional groups and to solution ions not entering into probe films is finally proposed.     

Perception of edges and visual texture in the camouflage of the common cuttlefish, Sepia officinalis

The cuttlefish, Sepia officinalis, provides a fascinating opportunity to investigate the mechanisms of camouflage as it rapidly changes its body patterns in response to the visual environment. We investigated how edge information determines camouflage responses through the use of spatially high-pass filtered 'objects' and of isolated edges. We then investigated how the body pattern responds to objects defined by texture (second-order information) compared with those defined by luminance. We found that (i) edge information alone is sufficient to elicit the body pattern known as Disruptive, which is the camouflage response given when a whole object is present, and furthermore, isolated edges cause the same response; and (ii) cuttlefish can distinguish and respond to objects of the same mean luminance as the background. These observations emphasize the importance of discrete objects (bounded by edges) in the cuttlefish's choice of camouflage, and more generally imply that figure-ground segregation by cuttlefish is similar to that in vertebrates, as might be predicted by their need to produce effective camouflage against vertebrate predators.     

微生物活细胞快速检测的新技术研究

微生物活菌分为繁殖能力的活菌和有代谢活动但没有繁殖能力的活菌。传统的平板计数方法无法对有代谢活动但没有繁殖能力的活菌进行准确定量分析。本文综述了微生物活细胞检测新技术的研究进展,包括以PCR为基础的新技术和荧光活化细胞分选术与流式细胞术结合的新技术。     

志贺菌毒力检测的常用方法

志贺菌属的细菌以人类为特异性宿主,感染人类肠上皮细胞,多导致痉挛性腹痛、腹泻、发烧等症状,是细菌性痢疾最为常见的病原菌。志贺菌的致病机理主要由其Ⅲ型分泌系统调节。志贺菌侵袭力的高低及毒力强弱决定了其致病性的强弱。我们简要介绍志贺菌属细菌的毒力检测方法。     

Comparison of accuracy of ultrasonography, progesterone, and pregnancy-associated glycoprotein tests for pregnancy diagnosis in semidomesticated reindeer

The aim of the study was to compare transrectal ultrasound with progesterone (P4) and pregnancy-associated glycoproteins (PAGs) as pregnancy detection methods for semidomesticated reindeer (Rangifer tarandus tarandus) in field conditions. Female reindeer (n = 195) were scanned transrectally by a 7.5-MHz linear array transducer, and blood was sampled either in December 2005 (n = 33), December 2006 (n = 92), or January 2007 (n = 70) during early or mid gestation. Plasma levels of P4 and PAGs were assessed by radioimmunoassay (RIA). Based on calving records, the sensitivity, specificity, predictive values, and the overall accuracy of the three tests were calculated. The overall calving rate calculated from the calving records was 86.2%. The overall accuracy of transrectal ultrasound was 99.5%. The sensitivity and specificity of transrectal ultrasound were 99.4% and 100%, respectively. In the plasma P4 test, the threshold level of 5.0 nmol/L gave the highest overall accuracy (94.9%). The sensitivity of the P4 test decreased from 96.4% to 81.5%, when the threshold level increased from 5.0 nmol/L to 8.0 nmol/L, while the specificity remained at 85.2% over the range of these cutoff values. The overall accuracy of the plasma PAG test decreased from 96.4% to 64.1% when the plasma PAG threshold level increased from 0.5 ng/mL to 3.5 ng/mL, whereas sensitivity decreased from 99.4% to 58.3%. Specificity increased from 77.8% to 100% when the plasma PAG threshold level reached 3.0 ng/mL. Transrectal ultrasound showed higher diagnostic values than those of plasma P4-RIA and PAG-RIA in diagnosing pregnancy of reindeer, with the advantage that diagnoses can be made in real time in field conditions.     

Pregnancy patterns during the early fetal period in high producing dairy cows treated with GnRH or progesterone

In order to explore pregnancy patterns in high producing dairy cows treated with GnRH or progesterone at pregnancy diagnosis (Days 28-34), two consecutive experiments were designed. In Experiment 1, cows bearing a single embryo were randomly assigned to a PRID (n = 40; cows fitted with a progesterone releasing intra-vaginal device for 28 days), GnRH (n = 40; cows receiving GnRH) or Control (n = 26; untreated cows) group. PRID treatment led to a rise in plasma progesterone concentrations in the 7 days following the onset of treatment compared to the other two groups. In Experiment 2, in which we also examined twin pregnancies, animals were randomly assigned to PRID (n = 312) or GnRH (n = 294) treatment groups. Treatments were the same as described for Experiment 1. Logistic regression procedures revealed that in cows with a single corpus luteum, the probability of pregnancy loss between the first (Days 28-34) and second (Days 65-62) pregnancy diagnosis decreased by a factor of 0.51 in the PRID group compared to the GnRH group. However, in cows with two or more corpora lutea, PRID treatment increased the likelihood of pregnancy loss by a factor of three, compared to GnRH treatment. In cows carrying twins, the conceptus reduction rate was higher (P = 0.02) for the GnRH (36%) than for the PRID (16.4%) group. Formation of a new corpus luteum was recorded in 17.7% of cows in the GnRH group. Our results indicate that compared to GnRH treatment, progesterone treatment given at pregnancy diagnosis in high producing dairy cows, reduced by a factor of 0.51 and increased by a factor of 3 the probability of pregnancy loss in cows with a single or with two or more corpora lutea, respectively, and reduced the conceptus reduction rate in cows carrying twins. The practical implications of our findings are that in herds with a high incidence of early fetal loss of a non-infectious nature, treatment at the time of pregnancy diagnosis with PRID in cows with one corpus luteum and with GnRH in cows with two or more corpora lutea should offer considerable benefits.     

A model of visual detection of angular speed for bees

A fly or bee's responses to widefield image motion depend on two basic parameters: temporal frequency and angular speed. Rotational optic flow is monitored using temporal frequency analysers, whereas translational optic flow seems to be monitored in terms of angular speed. Here we present a possible model of an angular speed detector which processes input signals through two parallel channels. The output of the detector is taken as the ratio of the two channels’ outputs. This operation amplifies angular speed sensitivity and depresses temporal frequency tuning. We analyse the behaviour of two versions of this model with different filtering properties in response to a variety of input signals. We then embody the detector in a simulated agent's visual system and explore its behaviour in experiments on speed control and odometry. The latter leads us to suggest a new algorithm for optic flow driven odometry.     

Recording movement and activity pattern of a White-tailed Sea Eagle ( Haliaeetus albicilla ) by a GPS datalogger

For the first time, we measured the home range size and activity pattern of a White-tailed Sea Eagle (WTSE) by GPS telemetry. Positions were recorded three times a day and the activity pattern were continuously recorded by two acceleration sensors. From July to January, we obtained 475 positions and calculated a 95% kernel home range of 4.53 km² and a 95% minimum convex polygon of 8.22 km², indicating a rather small area explained by an optimal habitat and by the much more precise location method used here compared to reports in the literature. Biorhythmic analysis of activity data revealed nearly no night-activity, high day-activity with no fixed daily pattern and a strong 24-h period of activity. The stability and synchronisation between the eagle's activity and the environmental 24-h period was evaluated by calculating the degrees of functional coupling (DFC) and the harmonic part (HP). Mostly, DFC was 100% (meaning that the different physiological and behavioural functions are completely synchronised to each other and to the environmental 24-h period) and the few incursions of the DFC we assumed to be caused by clinically relevant lead intoxications. The agonal stage of the WTSE was indicated by a daily decreasing activity level and HPs and highly modified day–night relationship, and decreasing DFCs at the beginning and at the end of dying process, representing changes in the activity structure. The underlying reason for the behavioural changes was found to be a lethal lead intoxication due to an oral ingestion of particles of rifle ammunition. The new technology of a combined GPS receiver and an acceleration sensor allows the automatic measuring of positions and activity of wild animals at a very precise level over prolonged periods which cannot be achieved by manpower.     

应用小波变换检测细胞显微荧光图像中的囊泡

文章提出了一种用小波变换来检测生物荧光图像中囊泡的方法。作者用à trous小波对图像进行小波变换,然后求出每层系数的中值绝对偏差σ,并用t=kσ/0.67作为阈值对每层系数进行门限滤波,然后通过提取小波变换系数来重构图像。通过设计实验与常用的“rolling ball”算法对比,发现小波变换算法在低信噪比的情况下,具有更好的灵敏度;对于形状大小不同的信号,具有更好的稳定性;而且对于信号的细节信息具有更好的保真性。