Compilation of Published Estimates of Annual Geocenter Motions Using Space Geodesy

The definition of the term "geocenter motion" depends on the adopted origin of the reference frame. Common reference frames used in Space Geodesy include: the center of mass of the whole Earth (CM), the center of mass of the Solid Earth without mass load (CE), and the center of figure of the outer surface of the Solid Earth (CF). There are two established definitions of the term geocenter: one, the vector offset of CF relative to CM and, two, the reverse, the vector offset of CM relative to CF. Obviously, their amplitude is the same and their phase differs by 180 deg. Following Dong et al. [2003], we label the first X(sub CF, sup CM) and the second X(sup CF, sup CM) (i.e., the superscript represents the frame, the subscript represents any point in the frame)

Risky Banking: Optimal Loan Quantity and Portfolio Quality Choices

In this paper we construct a model of a "risky bank". The bank faces excess demand in the loan market, can sort loan applicants by an observable measure of quality, and faces a small but positive probability of default on its loan portfolio. The bank uses two policies to allocate credit: - Tighten restrictions on loan quality - Limit the number of loans of a given quality We show that the level of default risk and other structural conditions have important e®ects on the market for loanable funds and the bank's optimal policies (loan rates, deposit rates, and lending standards). The structural conditions that we examine are monitoring costs, returns on alternative investments, firms' minimum funding requirements, and the level of the reserve requirement. The model provides insight into several stylized facts observed in loan markets, especially in developing countries.Facultad de Ciencias Económica

Risky Banking: Optimal Loan Quantity and Portfolio Quality Choices

In this paper we construct a model of a "risky bank". The bank faces excess demand in the loan market, can sort loan applicants by an observable measure of quality, and faces a small but positive probability of default on its loan portfolio. The bank uses two policies to allocate credit: - Tighten restrictions on loan quality - Limit the number of loans of a given quality We show that the level of default risk and other structural conditions have important e®ects on the market for loanable funds and the bank's optimal policies (loan rates, deposit rates, and lending standards). The structural conditions that we examine are monitoring costs, returns on alternative investments, firms' minimum funding requirements, and the level of the reserve requirement. The model provides insight into several stylized facts observed in loan markets, especially in developing countries.Facultad de Ciencias Económica

Ozeano Artikoko bankisaren beherakada: behaketak berrikusten, kausa fisikoak ulertzen eta etorkizuneko aldaketak iragartzen

Ozeano Artikoa bankisa mehe batez estalita dago. Bankisa klima polarra taxutzen duen faktore garrantzitsuetako bat da, eta eragina izan dezake klima-sistema globalean ere. Garrantzi hori dela eta, beharrezkoa da Artikoko bankisa horren egoerari begiratzea eta hura ulertzea eta aurreikustea. Behaketek argi eta garbi erakutsi dute izotzaren hedadura eta lodiera murrizten ari direla eta izotz iraunkorra zena aldikako izotz ari dela bilakatzen. Inolako zalantza-izpirik gabe, Artikoko bankisa gainbehera nabarian dago. Bankisaren gainbehera hori ulertzeko, aldaketa horien kausa izan litezkeen prozesu termodinamiko eta dinamiko giltzarriak aztertu behar dira. Prozesuon artean daude, besteak beste, faktore fisikoak (adibidez, epeltzeko joerak), atmosferako eta ozeanoko zirkulazioan gertatutako aldaketak, ozeanoaren gainazalera iristen den eguzki-erradiazio handiagoa eta horri lotutako izotz-albedoaren berrelikadura. Gaur egungo ereduek aurreikusten dute mende hau amaitu baino lehen Ozeano Artikoa izotzik gabe geratuko dela udako urtze-garaiaren bukaeran. Behaketek, baina, erakusten dute bankisaren beherakada ez dela ereduek iragarritako abiaduran gertatzen ari, azkarrago baizik, eta agerian uzten dute ereduak hobetzeko premia. Artikoko bankisaren gainbeherak ondorio garrantzitsuak ditu Artikoko eta Lurreko klima-sistemetan, eta, gainera, gero eta erronka handiagoak ezartzen ditu alor sozioekonomikoan, politikoan eta ekologikoan

Risky Banking: Optimal Loan Quantity and Portfolio Quality Choices

In this paper we construct a model of a "risky bank". The bank faces excess demand in the loan market, can sort loan applicants by an observable measure of quality, and faces a small but positive probability of default on its loan portfolio. The bank uses two policies to allocate credit: - Tighten restrictions on loan quality - Limit the number of loans of a given quality We show that the level of default risk and other structural conditions have important e®ects on the market for loanable funds and the bank's optimal policies (loan rates, deposit rates, and lending standards). The structural conditions that we examine are monitoring costs, returns on alternative investments, firms' minimum funding requirements, and the level of the reserve requirement. The model provides insight into several stylized facts observed in loan markets, especially in developing countries.Facultad de Ciencias Económica

VLBI measurement of the vector baseline between geodetic antennas at Kokee Park Geophysical Observatory, Hawaii

We measured the components of the 31-m-long vector between the two Very-Long-Baseline Interferometry (VLBI) antennas at the Kokee Park Geophysical Observatory (KPGO), Hawaii, with approximately 1 mm precision using phase-delay observables from dedicated VLBI observations in 2016 and 2018. The two KPGO antennas are the 20 m legacy VLBI antenna and the 12 m VLBI Global Observing System (VGOS) antenna. Independent estimates of the vector between the two antennas were obtained by the National Geodetic Survey (NGS) using standard optical surveys in 2015 and 2018. The uncertainties of the latter survey were 0.3 and 0.7 mm in the horizontal and vertical components of the baseline, respectively. We applied corrections to the measured positions for the varying thermal deformation of the antennas on the different days of the VLBI and survey measurements, which can amount to 1 mm, bringing all results to a common reference temperature. The difference between the VLBI and survey results are 0.2 +/- 0.4 mm, -1.3 +/- 0.4 mm, and 0.8 +/- 0.8 mm in the East, North, and Up topocentric components, respectively. We also estimate that the Up component of the baseline may suffer from systematic errors due to gravitational deformation and uncalibrated instrumental delay variations at the 20 m antenna that may reach +/-10 mm and -2 mm, respectively, resulting in an accuracy uncertainty on the order of 10 mm for the relative heights of the antennas. Furthermore, possible tilting of the 12 m antenna increases the uncertainties in the differences in the horizontal components to 1.0 mm. These results bring into focus the importance of (1) correcting to a common reference temperature the measurements of the reference points of all geodetic instruments within a site, (2) obtaining measurements of the gravitational deformation of all antennas, and (3) monitoring local motions of the geodetic instruments.Comment: 34 pages, 4 figures, to be published in Journal of Geodes

New reference ranges for interpreting forced expiratory manoeuvres in infants and implications for clinical interpretation: a multicentre collaboration

The raised volume rapid thoracoabdominal compression (RVRTC) technique is commonly used to obtain full forced expiratory manoeuvres from infants, but reference equations derived from 'in-house' equipment have been shown to be inappropriate for current commercially available devices

Spatial and Temporal Melt Variability at Helheim Glacier, East Greenland, and Its Effect on Ice Dynamics

Understanding the behavior of large outlet glaciers draining the Greenland Ice Sheet is critical for assessing the impact of climate change on sea level rise. The flow of marine-terminating outlet glaciers is partly governed by calving-related processes taking place at the terminus but is also influenced by the drainage of surface runoff to the bed through moulins, cracks, and other pathways. To investigate the extent of the latter effect, we develop a distributed surface-energy-balance model for Helheim Glacier, East Greenland, to calculate surface melt and thereby estimate runoff. The model is driven by data from an automatic weather station operated on the glacier during the summers of 2007 and 2008, and calibrated with independent measurements of ablation. Modeled melt varies over the deployment period by as much as 68% relative to the mean, with melt rates approximately 77% higher on the lower reaches of the glacier trunk than on the upper glacier. We compare melt variations during the summer season to estimates of surface velocity derived from global positioning system surveys. Near the front of the glacier, there is a significant correlation (on \u3e95% levels) between variations in runoff (estimated from surface melt) and variations in velocity, with a 1 day delay in velocity relative to melt. Although the velocity changes are small compared to accelerations previously observed following some calving events, our findings suggest that the flow speed of Helheim Glacier is sensitive to changes in runoff. The response is most significant in the heavily crevassed, fast-moving region near the calving front. The delay in the peak of the cross-correlation function implies a transit time of 12-36 h for surface runoff to reach the bed

The "footloose" mechanism : iceberg decay from hydrostatic stresses

Authors are grateful to the Office of Naval Research High Latitude Program for supporting the University of Cambridge participation through the MIZ‐DRI project, grant N00014‐12‐1‐0130. T.J.W.W. further acknowledges ONR grant N00014‐13‐1‐0469.We study a mechanism of iceberg breakup that may act together with the recognized melt and wave-induced decay processes. Our proposal is based on observations from a recent field experiment on a large ice island in Baffin Bay, East Canada. We observed that successive collapses of the overburden from above an unsupported wavecut at the iceberg waterline created a submerged foot fringing the berg. The buoyancy stresses induced by such a foot may be sufficient to cause moderate-sized bergs to break off from the main berg. A mathematical model is developed to test the feasibility of this mechanism. The results suggest that once the foot reaches a critical length, the induced stresses are sufficient to cause calving. The theoretically predicted maximum stable foot length compares well to the data collected in situ. Further, the model provides analytical expressions for the previously observed "rampart-moat" iceberg surface profiles.Publisher PDFPeer reviewe