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Global Warming Detected by Tree Rings from Mongolia
Nachin, Baatarbileg,Jacoby, Gordon C. Korea Association For Quaternary Research 2003 제사기학회지 Vol.17 No.2
In the year 2000 we culminated a successful five year investigation of climate change by completing a preliminary east-west transect across Mongolia. An earlier tree-ring study at Tarvagatay Pass, Mongolia indicated unusual warming during the 20th century similar to other paleo-investigations of the northern hemisphere. This record had represented one of the few tree-ring records for central Asia. New data from several sites in western Mongolia confirmed the preliminary temperature. The highest twenty-year growth period for the composite record is from 1973-1994. The western Mongolian record was significantly correlated with the Taimyr Peninsula and two northern hemisphere temperature reconstructions reflecting large-scale temperature patterns while showing some important regional differences. These differences should prove useful for climate models. We have also developed a millennial length temperature-sensitive record at the Solongotyin Davaa site (formerly Tarvagatay Pass) using relict wood and living trees. Conspicuous features over the last 1000 years are a century scale temperature decline punctuated by the end of the Little Ice Age in the late-1800s and 20th century warming. The record also shows a cold period early in the 12th century and warm intervals late in the 10th, early in the 15th and at end of the 18th centuries. Despite a limited sample size before 900 AD, the long Solongotyin Davaa record is useful in indicating severe cold events and suggests some cold intervals nearly as severe. These tree ring series, spanning much of the circumpolar northern treeline, have been compiled to create a long-term reconstruction of the Earth's temperature over centuries. The new chronology, in addition to its value as a detailed record of Mongolian climate, provides independent corroboration for such hemispheric and global reconstructions and their indications of unusual warming during the 20th century.
Temperature Fluctuations Over the Past 2000 Years in Western Mongolia
Pederson, Neil,Jacoby, Gordon C.,D′Arrigo, Rosanne.,Frank, David,Buckley, Brendan,Nachin, Baatarbileg,Chultem, Dugarjav,Renchin, Mijiddorj Korea Association For Quaternary Research 2003 제사기학회지 Vol.17 No.2
Much of northern Asia is lacking in high-resolution palaeoclimatic data coverage. This vast region thus represents a sizeable gap in data sets used to reconstruct hemispheric-scale temperature trends for the past millennium. To improve coverage, we present a regional-scale composite of four tree-ring width records of Siberian pine and Siberian larch from temperature-sensitive alpine timber-line sites in Mongolia. The chronologies load closely in principal components analysis (PCA) with the first eigenvector accounting for over 53% of the variance from ad 1450 to 1998. The 20-year interval from 1974 to 1993 is the highest such growth period in this composite record, and 17 of the 20 highest growth years have occurred since 1946. Thus these trees, unlike those recently described at some northern sites, do not appear to have lost their temperature sensitivity, and suggest that recent decades have been some of the warmest in the past 500 years for this region. There are, however, comparable periods of inferred, local warmth for individual sites, e.g., in 1520-1580 and 1760-1790. The percent common variance between chronologies has increased through time and is highest (66.1%) in the present century. Although there are obvious differences among the individual chronologies, this result suggests a coherent signal which we consider to be related to temperature. The PCA scores show trends which strongly resemble those seen in recent temperature reconstructions for the Northern Hemisphere, very few of which included representation from Eurasia east of the Ural Mountains. The Mongolia series therefore provides independent corroboration for these reconstructions and their indications of unusual wanning during the twentieth century.
Loss-of-function mutations in sodium channel Na<sub>v</sub>1.7 cause anosmia
Weiss, Jan,Pyrski, Martina,Jacobi, Eric,Bufe, Bernd,Willnecker, Vivienne,Schick, Bernhard,Zizzari, Philippe,Gossage, Samuel J.,Greer, Charles A.,Leinders-Zufall, Trese,Woods, C. Geoffrey,Wood, John N. Nature Publishing Group, a division of Macmillan P 2011 Nature Vol.472 No.7342
Loss of function of the gene SCN9A, encoding the voltage-gated sodium channel Na<SUB>v</SUB>1.7, causes a congenital inability to experience pain in humans. Here we show that Na<SUB>v</SUB>1.7 is not only necessary for pain sensation but is also an essential requirement for odour perception in both mice and humans. We examined human patients with loss-of-function mutations in SCN9A and show that they are unable to sense odours. To establish the essential role of Na<SUB>v</SUB>1.7 in odour perception, we generated conditional null mice in which Na<SUB>v</SUB>1.7 was removed from all olfactory sensory neurons. In the absence of Na<SUB>v</SUB>1.7, these neurons still produce odour-evoked action potentials but fail to initiate synaptic signalling from their axon terminals at the first synapse in the olfactory system. The mutant mice no longer display vital, odour-guided behaviours such as innate odour recognition and avoidance, short-term odour learning, and maternal pup retrieval. Our study creates a mouse model of congenital general anosmia and provides new strategies to explore the genetic basis of the human sense of smell.
The localization and photosensitization of modified chlorin photosensitizers in artificial membranes
Ben Dror, Shimshon,Bronshtein, Irena,Garini, Yuval,O'Neal, William G.,Jacobi, Peter A.,Ehrenberg, Benjamin Korean Society of Photoscience 2009 Photochemical & photobiological sciences Vol.8 No.3
In this work we investigate the localization and photophysical properties of twelve synthetically derived chlorins in artificial membranes, with the goal of designing more effective photosensitizers for photodynamic therapy (PDT). The studied chlorins incorporate substituents of varying lipophilicity at the $C_5$-meso-position (H to $C_5H_{11}$), while the $C_{13}$- and $C_{17}$-positions have carboxylate "anchoring" groups tethered to the tetrapyrrole by alkyl chains $(CH_2)_n$ (n = 1-3). It was found that as n increases, the chromophoric part of the molecule, and thus the point of generation of singlet oxygen, is located at a deeper position in the bilayer. The vertical insertion of the sensitizers was assessed by two fluorescence-quenching techniques: by iodide ions that come from the aqueous phase and by spin-probe-labeled phospholipids that are incorporated into the bilayer, using the parallax method. These results demonstrate that elongation of the side chains endows the modified molecules with a larger affinity for artificial membranes and also causes the tetrapyrrole ring to be localized deeper in the lipid membrane. This location leads to a higher effective quantum yield for the chemical reaction of singlet oxygen with its chemical target 9,10-dimethylanthracene (DMA).