Current measurement by real-time counting of single electrons

The fact that electrical current is carried by individual charges has been known for over 100 years, yet this discreteness has not been directly observed so far. Almost all current measurements involve measuring the voltage drop across a resistor, using Ohm's law, in which the discrete nature of charge does not come into play. However, by sending a direct current through a microelectronic circuit with a chain of islands connected by small tunnel junctions, the individual electrons can be observed one by one. The quantum mechanical tunnelling of single charges in this one-dimensional array is time correlated, and consequently the detected signal has the average frequency f = I/e, where I is the current and e is the electron charge. Here we report a direct observation of these time-correlated single-electron tunnelling oscillations, and show electron counting in the range 5 fA-1 pA. This represents a fundamentally new way to measure extremely small currents, without offset or drift. Moreover, our current measurement, which is based on electron counting, is self-calibrated, as the measured frequency is related to the current only by a natural constant.     

Oxidative stress and impaired oligodendrocyte precursor cell differentiation in neurological disorders

Cellular and Molecular Life Sciences - Oligodendrocyte precursor cells (OPCs) account for 5% of the resident parenchymal central nervous system glial cells. OPCs are not only a back-up for the loss...     

Action Research: Its History and Relationship to Scientific Methodology

Scientific Methodology (SM) has long suited those who favour analytical and quantitative research in management. Thus the dilemma between the rigour and relevance of contemporary management research methods is fuelled by action researchers who keep wanting to contrast Action Research (AR) with SM. This paper presents a Western philosophical view on the development of belief systems and theory-based methods over time. It thus links the progressive and cumulative development of SM with the contemporary AR methodology. In doing this it presents a different point of view—that the traditions of SM and AR have much closer relationships than people often give them credit for.     

你还是自己资产的最佳所有者吗

<正>观点提要·业务的最佳所有者在不断变化,因此,任何企业都应该定期收购和出售业务。·资产剥离会被视为承认企业经营失败,事实上股市一直在对资产剥离,无论是出售还是分拆,做出积极的回应。     

Impacts of intraseasonal oscillation on the onset and interannual variation of the Indian summer monsoon

The role of the intraseasonal oscillation (ISO) on the seasonal and interannual variations of the Indian summer monsoon is investigated based on the analysis of observational data. It is shown that the ISO significantly contributes to the establishment of low-level westerlies during the monsoon onset and developing periods. The effect of the ISO on the annual cycle of the monsoon is through nonlinear eddy momentum transport. On the interannual timescale, the Indian summer monsoon rainfall exhibits a significant out-of-phase relationship with the ISO intensity over the Indian monsoon region. In strong ISO years it appears the weak monsoon when there is an abnormal high over the India subcontinent in the lower troposphere. In weak ISO years there exists an abnormal low and the strong monsoon appears. Supported by National Basic Research Program of China (Grant No. 2006CB403602), National Natural Science Foundation of China (Grant Nos. 40225012 and 40775039) and Chinese COPES Program (Grant No. GYHY200706005)     

Action Research in Management—Ethical Dilemmas

This paper discusses the application of the guiding ethical principles for the conduct of research involving human subjects in an action research project in a membership-based community psychiatric disability organization. Action research is a collaborative process of critical inquiry between the researcher and the people in the situation, in this case the management executive. The relationship between the researcher and manager participants in a long-term action research project gives rise to ethical dilemmas related to participant selection and voluntary participation, informed consent, decision making, anonymity and confidentiality, conflicting and different needs. The process and strategies implemented to address them are discussed.     

Diffraction-unlimited all-optical imaging and writing with a photochromic GFP

Lens-based optical microscopy failed to discern fluorescent features closer than 200?nm for decades, but the recent breaking of the diffraction resolution barrier by sequentially switching the fluorescence capability of adjacent features on and off is making nanoscale imaging routine. Reported fluorescence nanoscopy variants switch these features either with intense beams at defined positions or randomly, molecule by molecule. Here we demonstrate an optical nanoscopy that records raw data images from living cells and tissues with low levels of light. This advance has been facilitated by the generation of reversibly switchable enhanced green fluorescent protein (rsEGFP), a fluorescent protein that can be reversibly photoswitched more than a thousand times. Distributions of functional rsEGFP-fusion proteins in living bacteria and mammalian cells are imaged at <40-nanometre resolution. Dendritic spines in living brain slices are super-resolved with about a million times lower light intensities than before. The reversible switching also enables all-optical writing of features with subdiffraction size and spacings, which can be used for data storage.