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A Possible Feedback Mechanism Involving the Arctic Freshwater,the Arctic Sea Ice,and the North Atlantic Drift

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Advances in Atmospheric Sciences 2004年第5期21卷 784-801页

作者： Odd helge OTTER helge DRANGE Nansen Environmental and Remote Sensing Center Edv. Griegsvei 3A5059 Bergen Bjerknes Centre for Climate Research Allégt. 55 5007 BergenNansen Environmental and Remote Sensing Center Edv. Griegsvei 3A5059 Bergen Bjerknes Centre for Climate Research Allégt. 55 5007 BergenGeophysical Institute University of Bergen Allégt. 70 5007 Bergen Nansen-Zhu International Research Centre Beijing 100029

Model studies point to enhanced warming and to increased freshwater ?uxes to high northern latitudes in response to global warming. In order to address possible feedbacks in the ice-ocean system in response to such changes, the combined e?ect of increased freshwater input to the Arctic Ocean and Arctic warming—the latter manifested as a gradual melting of the Arctic sea ice—is examined using a 3-D isopycnic coordinate ocean general circulation model. A suite of three idealized experiments is carried out: one control integration, one integration with a doubling of the modern Arctic river runo?, and a third more extreme case, where the river runo? is ?ve times the modern value. In the two freshwater cases, the sea ice thickness is reduced by 1.5–2 m in the central Arctic Ocean over a 50-year period. The modelled ocean response is qualitatively the same for both perturbation experiments: freshwater propagates into the Atlantic Ocean and the Nordic Seas, leading to an initial weakening of the North Atlantic Drift. Furthermore, changes in the geostrophic currents in the central Arctic and melting of the Arctic sea ice lead to an intensi?ed Beaufort Gyre, which in turn increases the southward volume transport through the Canadian Archipelago. To compensate for this southward transport of mass, more warm and saline Atlantic water is carried northward with the North Atlantic Drift. It is found that the increased transport of salt into the northern North Atlantic and the Nordic Seas tends to counteract the impact of the increased freshwater originating from the Arctic, leading to a stabilization of the North Atlantic Drift.

关键词： Arctic Ocean freshwater seaice North Atlantic Drift

The Effect of Diapycnal Mixing on the Ventilation and CFC-11 Uptake in the Southern Ocean

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Advances in Atmospheric Sciences 2004年第5期21卷 755-766页

作者： helge DRANGE Nansen Environmental and Remote Sensing Center Bergen Norway Nansen-Zhu International Research Centre Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029Bjerknes Centre for Climate Research Bergen Norway Geophysical Institute University of Bergen Bergen Norway

The Miami Isopycnic Coordinate Ocean Model (MICOM) is used to investigate the effect of diapycnal mixing on the oceanic uptake of CFC-11 and the ventilation of the surface waters in the Southern Ocean (south of 45°S). Three model experiments are performed: one with a diapycnal mixing coefficientK d (m2 s?1) of 2 × 10?7/N (Expt. 1), one withK d = 0 (Expt. 2), and one withK d = 5 × 10?8/N (Expt. 3),N (s?1) is the Brunt-V?is?l? frequency. The model simulations indicate that the observed vertical distribution of CFC-11 along 88°W (prime meridian at 0°E) in the Southern Ocean is caused by local ventilation of the surface waters and westward-directed (eastward-directed) isopycnic transport and mixing from deeply ventilated waters in the Weddell Sea region. It is found that at the end of 1997, the simulated net ocean uptake of CFC-11 in Expt. 2 is 25% below that of Expt. 1. The decreased uptake of CFC-11 in the Southern Ocean accounts for 80% of this difference. Furthermore, Expts. 2 and 3 yield far more realistic vertical distributions of the ventilated CFC-waters than Expt. 1. The experiments clearly highlight the sensitivity of the Southern Ocean surface water ventilation to the distribution and thickness of the simulated mixed layer. It is argued that inclusion of CFCs in coupled climate models could be used as a test-bed for evaluating the decadal-scale ocean uptake of heat and CO2.

关键词： chlorofluorocarbons CFC-11 diapycnal mixing ocean modelling ocean ventilation Southern Ocean transient tracers

Simulating the Effects of the 1991 Mount Pinatubo Volcanic Eruption Using the ARPEGE Atmosphere General Circulation Model

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Advances in Atmospheric Sciences 2008年第2期25卷 213-226页

作者： Odd helge OTTER Nansen Environmental and Remote Sensing Center Thorm0hlensgt. 47 5006 Bergen Norway Bjerknes Centre for Climate Research Allegt. 55 5007 Bergen Norway

The climate changes that occured following the volcanic eruption of Mount Pinatubo in the Phillippines on 15 June 1991 have been simulated using the ARPEGE atmosphere general circulation model （AGCM）. The model was forced by a reconstructed spatial-time distribution of stratospheric aerosols intended for use in long climate simulations. Four statistical ensembles of the AGCM simulations with and without volcanic aerosols over a period of 5 years following the eruption have been made, and the calculated fields have been compared to available observations. The model is able to reproduce some of the observed features after the eruption, such as the winter warming pattern that was observed over the Northern Hemisphere （NH） during the following winters. This pattern was caused by an enhanced Equator-to-pole temperature gradient in the stratosphere that developed due to aerosol heating of the tropics. This in turn led to a strengthening of the polar vortex, which tends to modulate the planetary wave field in such a way that an anomalously positive Arctic Oscillation pattern is produced in the troposphere and at the surface, favouring warm conditions over the NH. During the summer, the model produced a more uniform cooling over the NH.

关键词： volcanic aerosol climate Mount Pinatubo Arctic Oscillation

A Preliminary Study on the Relationship Between Arctic Oscillation and Daily SLP Variance in the Northern Hemisphere During Wintertime

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Advances in Atmospheric Sciences 2005年第3期22卷 313-327页

作者：龚道溢 helge DRANGE Key Laboratory of Environmental Change and Natural DisasterCollege of Resources Science and Technology Beijing Normal University Beijing 100875 Bjerknes Centre for Climate Research/Nansen Environmental and Remote Sensing CenterUniversity of Bergen Norway

In the present study, the authors investigated the relationship between the Arctic Oscillation (AO) and the high-frequency variability of daily sea level pressures in the Northern Hemisphere in winter (November through March), using NCEP/NCAR reanalysis datasets for the time period of 1948/49-2000/01. High-frequency signals are defined as those with timescales shorter than three weeks and measured in terms of variance, for each winter for each grid. The correlations between monthly mean AO index and high-frequency variance are conducted. A predominant feature is that several regional centers with high correlation show up in the middle to high latitudes. Significant areas include mid- to high-latitude Asia centered at Siberia, northern Europe and the middle-latitude North Atlantic east of northern Africa. Their strong correlations can also be confirmed by the singular value decomposition analysis of covariance between mean SLP and high-frequency variance. This indicates that the relationship of AO with daily Sea Level Pressure (SLP) is confined to some specific regions in association with the inherent atmospheric dynamics. In middle-latitude Asia, there is a significant (at the 95% level) trend of variance of-2.26% (10 yr)-1. Another region that displays a strong trend is the northwestern Pacific with a significant rate of change of 0.80% (10 yr)-1. If the winter of 1948/49, an apparent outlier, is excluded, a steady linear trend of +1.51% (10 yr)-1 shows up in northern Europe. The variance probability density functions (PDFs) are found to change in association with different AO phases. The changes corresponding to high and low AO phases, however, are asymmetric in these regions. Some regions such as northern Europe display much stronger changes in high AO years, whereas some other regions such as Siberia show a stronger connection to low AO conditions. These features are supported by ECMWF reanalysis data. However, the dynamical mechanisms involved in the AO-high fr

关键词： Arctic Oscillation sea level pressure (SLP) Northern Hemisphere synoptic variance

The CLE40 and CRN/CLV2 Signaling Pathways Antagonistically Control Root Meristem Growth in Arabidopsis

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Molecular Plant 2014年第11期7卷 1619-1636页

作者： helge Pallakies Rudiger Simon Institute for Developmental Genetics and Cluster of Excellence on Plant Sciences (CEPLAS) Universitatsstr. 1 Heinrich-Heine University40225 D~sseldorf Germany

Differentiation processes in the primary root meristem are controlled by several signaling pathways that are regulated by phytohormones or by secreted peptides. Long-term maintenance of an active root meristem requires that the generation of new stem cells and the loss of these from the meristem due to differentiation are precisely coordinated. Via phenotypic and large-scale transcriptome analyses of mutants, we show that the signaling peptide CLE40 and the recep- tor proteins CLV2 and CRN act in two genetically separable pathways that antagonistically regulate cell differentiation in the proximal root meristem. CLE40 inhibits cell differentiation throughout the primary root meristem by controlling genes with roles in abscisic acid, auxin, and cytokinin signaling. CRN and CLV2 jointly control target genes that promote cell differentiation specifically in the transition zone of the proximal root meristem. While CRN and CLV2 are not acting in the CLE40 signaling pathway under normal growth conditions, both proteins are required when the levels of CLE40 or related CLE peptides increase. We show here that two antagonistically acting pathways controlling root meristem differentiation can be activated by the same peptide in a dosage-dependent manner.

关键词： root meristem transcriptomics CLE40 CRN/CLV2 signaling peptides phytohormones.

Contrast-enhanced and targeted ultrasound

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World Journal of Gastroenterology 2011年第1期17卷 28-41页

作者： Michiel Postema Odd helge Gilja Emmy Noether Research Group Institute of Medical EngineeringDepartment of Electrical Engineering and Information SciencesRuhr-Universit t Bochum44780 BochumGermany Department of Physics and Technology Un versity of Bergen5007 BergenNorway Department of Engineering The University of HullKingston upon Hull HU6 7RXUnited Kingdom Centre de Biophysique Moléculaire UPR 4301 CNRS affiliated to the University of Orléans45071 OrléansFrance National Center for Ultrasound in Gastroenterology Department of MedicineHaukeland University Hospital5021 BergenNorway Institute of Medicine University of Bergen 5007 BergenNorway

Ultrasonic imaging is becoming the most popular medical imaging modality,owing to the low price per examination and its ***,blood is a poor scatterer of ultrasound waves at clinical diagnostic transmit *** perfusion imaging,markers have been designed to enhance the contrast in B-mode *** so-called ultrasound contrast agents consist of microscopically small gas bubbles encapsulated in biodegradable *** this review,the physical principles of ultrasound contrast agent microbubble behavior and their adjustment for drug delivery including sonoporation are ***,an outline of clinical imaging applications of contrast-enhanced ultrasound is *** is a challenging task to quantify and predict which bubble phenomenon occurs under which acoustic condition,and how these phenomena may be utilized in ultrasonic *** by high-speed photography,our improved understanding of encapsulated microbubble behavior will lead to more sophisticated detection and delivery *** sophisticated methods use quantitative approaches to measure the amount and the time course of bolus or reperfusion curves,and have shown great promise in revealing effective tumor responses to anti-angiogenic drugs in humans before tumor shrinkage *** are beginning to be accepted into clinical *** the long term,targeted microbubbles for molecular imaging and eventually for directed anti-tumor therapy are expected to be tested.

关键词： Ultrasound Drug delivery systems Drug targeting Sonoporation Contrast media Liver Pancreas Gastrointestinal tract

Sensitivity of East Asian Climate to the Progressive Uplift and Expansion of the Tibetan Plateau Under the Mid-Pliocene Boundary Conditions

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Advances in Atmospheric Sciences 2008年第5期25卷 709-722页

作者：姜大膀丁仲礼 helge DRANGE 郜永祺 Nansen-Zhu International Research Centre Institute of Atmospheric PhysicsChinese Academy of Sciences Institute of Geology and Geophysics Chinese Academy of Sciences Nansen Environmental and Remote Sensing Centre Bergen N-5006 Norway

A global atmospheric general circulation model has been used to perform eleven idealized numerical experiments, i.e., TP10, TP10, .., TP100, corresponding to different percentages of the Tibetan Plateau altitude. The aim is to explore the sensitivity of East Asian climate to the uplift and expansion of the Tibetan Plateau under the reconstructed boundary conditions for the mid-Pliocene about 3 Ma ago. When the plateau is progressively uplifted, global annual surface temperature is gradually declined and statistically significant cooling signals emerge only in the Northern Hemisphere, especially over and around the Tibetan Plateau, with larger magnitudes over land than over the oceans. On the contrary, annual surface temperature rises notably over Central Asia and most parts of Africa, as well as over northeasternmost Eurasia in the experiments TP60 to TP100. Meanwhile, the plateau uplift also leads to annual precipitation augmentation over the Tibetan Plateau but a reduction in northern Asia, the Indian Peninsula, much of Central Asia, parts of western Asia and the southern portions of northeastern Europe. Additionally, it is found that an East Asian summer monsoon system similar to that of the present initially exists in the TP60 and is gradually intensified with the continued plateau uplift. At 850 hPa the plateau uplift induces an anomalous cyclonic circulation around the Tibetan Plateau in summertime and two anomalous westerly currents respectively located to the south and north of the Tibetan Plateau in wintertime. In the mid-troposphere, similarto-modern spatial pattern of summertime western North Pacific subtropical high is only exhibited in the experiments TP60 to TP100, and the East Asian trough is steadily deepened in response to the progressive uplift and expansion of the Tibetan Plateau.

关键词： Tibetan Plateau uplift East Asian climate mid-Pliocene model

Auditory nerve preservation and regeneration in man:relevance for cochlear implantation

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Neural Regeneration Research 2015年第5期10卷 710-712页

作者： helge Rask-Andersen Wei Liu Department of Surgical Sciences Head and Neck SurgerySection of OtolaryngologyUppsala University Hospital Departments of Otolaryngology Uppsala University Hospital

Human hearing relies on 15,000 hair cells （HCs） or mecha- noreceptors sited in a 34 mm long helical shaped epithelial ridge. There may be several explanations for their vulner- ability in man and regrettably, they do not regenerate. Ap- proximately 35,000 bipolar neurons have their soma situated in the modiolus of the cochlea. Human afferents consist of two separate systems; one is represented by the large type I cells innervating the inner HCs （IHCs, n = 3,400） and the other one by the small type Ⅱcells innervating the outer HCs （OHCs, n = 12,000）. Type I spiral ganglion neurons （SGNs） constitute 96% of the afferent nerve population. Unlike in other mammals, their somas together with the pre- and post-somatic segments are unmyelinated. Type II nerve cell soma and fibers are unmyelinated.

关键词： cell Auditory nerve preservation and regeneration in man

Physiological and clinical significance of enterochromaffin-like cell activation in the regulation of gastric acid secretion

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World Journal of Gastroenterology 2007年第4期13卷 493-496页

作者： Guanglin Cui helge L Waldum Laboratory of Gastroenterology Institute of Clinical Medicine Faculty of Medicine University of Tromso Tromso Norway Department of Gastroenterology and Hepatology University Hospital of Trondheim Norwegian University of Science and Technology Trondheim Norway

Gastric acid plays an important role in digesting food （especially protein）, iron absorption, and destroying swallowed micro-organisms. H＋ is secreted by the oxyntic parietal cells and its secretion is regulated by endocrine, neurocrine and paracrine mechanisms. Gastrin released from the antral G cell is the principal physiological stimulus of gastric acid secretion. Activation of the enterochromaffin-like （ECL） cell is accepted as the main source of histamine participating in the regulation of acid secretion and is functionally and trophically controlled by gastrin, which is mediated by gastrin/CCK-2 receptors expressed on the ECL cell. However, longterm hypergastrinemia will induce ECL cell hyperplasia and probably carcinoids. Clinically, potent inhibitors of acid secretion have been prescribed widely to patients with acid-related disorders. Long-term potent acid inhibition evokes a marked increase in plasma gastdn levels, leading to enlargement of oxyntic mucosa with ECL cell hyperplasia. Accordingly, the induction of ECL cell hyperplasia and carcinoids remains a topic of considerable concern, especially in long-term use. In addition, the activation of ECL cells also induces another clinical concem, i.e., rebound acid hypersecretion after acid inhibition. Recent experimental and clinical findings indicate that the activation of ECL cells plays a critical role both physiologically and dinically in the regulation of gastric acid secretion.

关键词： Enterochromaffin-like cell Gastrin Gastric acid Gastric carcinoid Rebound acid hypersecretion