Laser Vaporization/Ionization Interface for Capillary Electrophoresis-Time-of-Flight Mass Spectrometry

Mass spectrometry (MS) is usually coupled on-line with capillary electrophoresis (CE) to analyze biomolecules by using electrospray ionization or continuous-flow fast-atom bombardment. We present a new design for laser vaporization/ionization time-of-flight mass spectrometry. CE, with its low flow rate (<1 μL/min), is highly compatible with MS, even if the total column effluent is introduced directly. A UV laser is used to vaporize and ionize the solution eluting from the column. There is no need to have a makeup solvent. Using this system, we have analyzed a group of amines and peptides. The concentration detection limit of serotonin is in the 10(-)(7) M level. The separation and identification of an amine mixture by CE/MS demonstrates the complementary nature of the information.     

The effects of combining classifiers with the same training statistics using Bayesian decision rules

Multiple classifier systems (MCS) are attracting increasing interest in the field of pattern recognition and machine learning. Recently, MCS are also being introduced in the remote sensing field where the importance of classifier diversity for image classification problems has not been examined. In this article, Satellite Pour l'Observation de la Terre (SPOT) IV panchromatic and multispectral satellite images are classified into six land cover classes using five base classifiers: contextual classifier, k-nearest neighbour classifier, Mahalanobis classifier, maximum likelihood classifier and minimum distance classifier. The five base classifiers are trained with the same feature sets throughout the experiments and a posteriori probability, derived from the confusion matrix of these base classifiers, is applied to five Bayesian decision rules (product rule, sum rule, maximum rule, minimum rule and median rule) for constructing different combinations of classifier ensembles. The performance of these classifier ensembles is evaluated for overall accuracy and kappa statistics. Three statistical tests, the McNemar's test, the Cochran's Q test and the Looney's F-test, are used to examine the diversity of the classification results of the base classifiers compared to the results of the classifier ensembles. The experimental comparison reveals that (a) significant diversity amongst the base classifiers cannot enhance the performance of classifier ensembles; (b) accuracy improvement of classifier ensembles can only be found by using base classifiers with similar and low accuracy; (c) increasing the number of base classifiers cannot improve the overall accuracy of the MCS and (d) none of the Bayesian decision rules outperforms the others.     

Chemical Modifications for a Next Generation of Nucleic Acid Aptamers

In the past three decades, in vitro systematic evolution of ligands by exponential enrichment (SELEX) has yielded many aptamers for translational applications in both research and clinical settings. Despite their promise as an alternative to antibodies, the low success rate of SELEX (∼30 %) has been a major bottleneck that hampers the further development of aptamers. One hurdle is the lack of chemical diversity in nucleic acids. To address this, the aptamer chemical repertoire has been extended by introducing exotic chemical groups, which provide novel binding functionalities. This review will focus on how modified aptamers can be selected and evolved, with illustration of some successful examples. In particular, unique chemistries are exemplified. Various strategies of incorporating modified building blocks into the standard SELEX protocol are highlighted, with a comparison of the differences between pre-SELEX and post-SELEX modifications. Nucleic acid aptamers with extended functionality evolved from non-natural chemistries will open up new vistas for function and application of nucleic acids.     

Magnetic Microsphere Scaffold-Based Soft Microbots for Targeted Mesenchymal Stem Cell Delivery (Small 32/2023)

A soft microbot assembled from individual magnetic microsphere scaffold (MMS) beads carrying mesenchymal stem cells (MSC) is navigated under magnetic actuation, where an oscillating field induces mechanical flexion to propel the microbot toward the target site. A seven-bead microbot attained a top translational speed of 205.6 µm s⁻¹ (0.068 body length s⁻¹) under 10 mT and 2 Hz field oscillation. The shallow flexion angle (10–24.5°) allows precision movements required to navigate narrow spaces. Upon arrival at the target site, the MMS beads unload their MSC cargo following exposure to a phosphate-buffered saline (PBS) solution, mimicking the extracellular fluid's sodium concentration. The released stem cells have excellent viability and vitality, promoting rapid healing (i.e., 83.2% vs 49%) in a scratch-wound assay. When paired with minimally invasive surgical methods, such as laparoscopy and endoscopic surgery, the microbot can provide precise stem cell delivery to hard-to-reach injury sites in the body to promote healing. Moreover, the microbot is designed to be highly versatile, with individual MMS beads customizable for cargoes of live cells, biomolecules, bionanomaterials, and pharmaceutical compounds for various therapeutic requirements.     

重庆购房户住宅需求取向分析

为了解决重庆房地产市场住宅市场供求不平衡这一个难题,我们提出了住宅产业化这个方案,但是在大规模的生产产业化住宅以前,首先必须知道重庆市居民对住宅的需求取向,正是因为这个原因,我们进行了一次问卷调查。问卷调查的目的是：摸清影响重庆市潜在购房户购房行为的因素,为重庆住宅产业化工程的实施构建一个模型。因此本文的目的就是：分析影响重庆市潜在购房户购房行为的因素,找出本市居民喜欢的住宅类型,我们研究组的总体研究目的是：立足于本地的资源,探索在重庆实施住宅产业化工程的可行性,如果可行,那么我们将在充分利用本地建筑材料的基础上,设计出切实可行的产业化住宅模型。在目前这个阶段,工作的重心是摸清重庆建筑业的概况,为下一步的研究铺平道路。而本文的中心是：找出本市居民喜欢的住宅类型。     

Partially Hydrogenated 1,1′‐Binaphthyl as Ligand Scaffold in Metal‐Catalyzed Asymmetric Synthesis

Although chiral binaphthyl‐type ligands are already known to be effective over a broad spectrum of reactions, they sometimes fail in providing high enantioselectivities in some catalytic asymmetric reactions. This article summarizes recent attempts to elevate their performance by partly hydrogenating the naphthyl components of the binaphthyl. The synthetic routes to some of these ligands are briefly outlined. Positive results are observed in asymmetric hydrogenation, alkylation, borane reduction, epoxidation and hetero‐Diels–Alder reactions. The function of the partially reduced binaphthyl skeleton, however, can sometimes be disadvantageous or ambiguous as illustrated in reactions such as asymmetric ring‐closing metathesis, 1,4‐conjugate addition, epoxidation, allylic alkylation, trimethylsilylcyanation, epoxide ring‐opening and hydroformylation.