Individual Anomalies Research Articles

Martian magnetic paleopoles: A geostatistical approach

Various attempts have been made to locate magnetic paleopoles on Mars by modeling individual magnetic field anomalies. In this study, a quite different approach, based on geostatistics, is taken. Discreet magnetic sources form magnetic doublet anomalies in the magnetic field that tend to align with the horizontal direction of magnetization. A semivariogram of radial field polarities on Mars indicates that magnetic field anomalies of opposite polarity tend to be separated by 14°. This phenomenon is interpreted to be due to the presence of magnetic doublet anomalies in the field. Accordingly, the autocovariances of the field polarity along longitudinal lines relative to over 1000 trial paleopole locations were examined. Magnetic paleopoles within about 50° of (230°E, 17°N) and (50°E, 17°S) were found to best explain the geostatistical structure of the polarity of the martian magnetic field.

Detection, identification and mapping of iron anomalies in brain tissue using X-ray absorption spectroscopy

This work describes a novel method for the detection, identification and mapping of anomalous iron compounds in mammalian brain tissue using X-ray absorption spectroscopy. We have located and identified individual iron anomalies in an avian tissue model associated with ferritin, biogenic magnetite and haemoglobin with a pixel resolution of less than 5 microm. This technique represents a breakthrough in the study of both intra- and extra-cellular iron compounds in brain tissue. The potential for high-resolution iron mapping using microfocused X-ray beams has direct application to investigations of the location and structural form of iron compounds associated with human neurodegenerative disorders--a problem which has vexed researchers for 50 years.

Feature removal and isolation in potential field data

SUMMARY With the aim of designing signal processing tools that act locally in space upon specific features of a signal, we compare two algorithms to remove or isolate individual anomalies in potential field profiles. The first method, based on multiscale edge analysis, leaves other features in the signal relatively untouched. A second method, based on iterative lateral continuation and subtraction of anomalies, accounts for the influence of adjacent anomalies on one another. This allows a potential field profile to be transformed into a number of single anomaly signals. Each single anomaly can then be individually processed, which considerably simplifies applications such as inversion and signal processing.

Identification of interplanetary coronal mass ejections at 1 AU using multiple solar wind plasma composition anomalies

We investigate the use of multiple simultaneous solar wind plasma compositional anomalies, relative to the composition of the ambient solar wind, for identifying interplanetary coronal mass ejection (ICME) plasma. We first summarize the characteristics of several solar wind plasma composition signatures (O7/O6, Mg/O, Ne/O, Fe charge states, He/p) observed by the ACE and Wind spacecraft within the ICMEs during 1996–2002 identified by Cane and Richardson [2003], hereafter CR03. We then develop a set of simple criteria that may be used to identify such compositional anomalies and hence potential ICMEs. To distinguish these anomalies from the normal variations seen in ambient solar wind composition, which depend on the wind speed, we compare observed compositional signatures with those “expected” in ambient solar wind with the same solar wind speed. This method identifies anomalies more effectively than the use of fixed thresholds. The occurrence rates of individual composition anomalies within ICMEs range from ∼70% for enhanced iron and oxygen charge states to ∼30% for enhanced He/p (>0.06) and Ne/O and are generally higher in magnetic clouds than other ICMEs. Intervals of multiple anomalies are usually associated with ICMEs and provide a basis for the identification of the majority of ICMEs. We estimate that CR03, who did not refer to composition data, probably identified ∼90% of the ICMEs present. However, around 10% of their ICMEs have weak compositional anomalies, suggesting that the presence of such signatures does not provide a necessary requirement for an ICME. We note a remarkably similar correlation between the Mg/O and O7/O6 ratios in hourly‐averaged data within both ICMEs and the ambient solar wind. This “universal” relationship suggests that similar processes produce the first‐ionization potential bias and enhanced ion freezing‐in temperatures in the source regions of both ICMEs and the ambient solar wind.

Layer‐wise attribution of vertical motion and the influence of potential‐vorticity anomalies on synoptic development

AbstractA methodology is presented for attributing vertical motion to potential vorticity (PV) in a explicit manner using the quasi‐geostrophic omega equation. The methodology is then used to determine the contribution individual PV anomalies make to the synoptic development. It is shown how the total vertical motion may be decomposed into self‐generating and interaction terms. The former correspond to vertical motion that arises from one PV region alone, whilst each of the interaction terms represent vertical motion due to the interaction of two different regions of PV. The method is applied to a number of cyclones studied in the Fronts and Atlantic Storm‐Tracks Experiment in order to determine the dynamical role of individual PV regions in cyclogenesis. For purposes of comparison, cyclones were chosen to be representative of the types (A, B and C) of an extended Petterssen–Smebye scheme devised by Deveson, Browning and Hewson. In terms of our new PV method, the Type A and B cyclones exhibit only subtle differences, with the upper‐level layer of PV playing a larger role in the case of the Type B cyclone. A much larger difference is apparent between the Type A and B cyclones on the one hand, and the Type C cyclone on the other: in the Type C cyclone, the upper‐level PV self‐generating term plays an important role, whereas in the Type A and B cases the influence of the upper‐level PV is largely restricted to the interaction terms. In all of the cases, the vertical motion attributable to the interaction between the low‐level PV and boundary thermal gradient was found to be large. Hence, from the viewpoint of instantaneous attribution, we conclude that the low‐level PV is always important. Copyright © 2003 Royal Meteorological Society

Integrated signal enhancements in magnetic investigation in archaeology

The magnetic method can be efficiently applied to archaeological investigation especially when the S/N ratio is enhanced appropriately. This study presents a model experiment and field examples of magnetic exploration in archaeology. By using appropriate measuring processes and filtering methods, the conventional and more recent magnetic prospecting techniques are successfully applied to the very shallow, small-scale investigations, which are used to locate and map archaeological targets. We focus on mapping the buried slate caskets in the alluvial environment, which is the most commonly encountered and readily preserved ones at the archaeological sites of Taiwan. The gradiometry and the inferred derivatives may resolve individual anomalies. Locations of the maxima determined by the 3-D analytic signals can be used to describe the outlines of the bodies that cause the anomalies. Furthermore, the susceptibility was very successful in mapping near-surface targets at the Chubin site. The magnetic results of the example at the Hutzushan site, compared to the GPR survey carried out by previous investigators, indicate that the GPR anomalies may be caused by other sources. The magnetic response of a casket can be displayed in various ways, depending on the pole distribution of the casket, the geometry, the magnetization direction and the orientation of buried casket. The processing methods may improve the data resolution, but precautions must be taken for the artifacts.

Prospective ranking of the sonographic markers for aneuploidy: data of 2143 prenatal cytogenetic diagnoses referred for abnormalities on ultrasound.

To design a scheme to rank sonographic anomalies as indicators of aneuploidy and record the distribution of data from 2143 prenatal amniotic fluid/chorionic villous sample diagnoses referred for karyotyping because of fetal anomalies detected with ultrasound. In all cases the records of sonographic anomalies were obtained prior to karyotyping. A cascade of seven prospective categories of ultrasound anomalies was chosen and the data were included in the highest compatible sonography category. The categories were in descending order: (I) combined central nervous system (CNS)/cranial shape and cardiac anomalies (excluding spina bifida and anencephaly); (II) key anomaly present (exomphalos/ intrauterine growth restriction/duodenal atresia/cystic hygroma/fetal hydrops/talipes--with other multiple anomalies); (III) CNS +/- other abnormality (excluding choroid plexus cyst, spina bifida, anencephaly); (IVa) increased nuchal translucency--first trimester +/- other abnormality; (IVb) increased nuchal thickening--second trimester +/- other abnormality; (V) cardiac anomaly +/- other abnormality; (VI) other markers of aneuploidy (pyelectasis/two vessel cord/echogenic bowel/short femur); and (VII) other (mostly isolated) malformations. There were 412/2143 (19.2%) chromosome abnormalities detected in this sonographically abnormal group. Overall, the prevalence of aneuploidy significantly ranged from 51 to 3% according to the above I-VII ultrasound categories and from approximately 1-80% for individual ultrasound anomalies. Likelihood ratios were derived for many ultrasound anomalies for several aneuploidy groups: trisomies of 13; 18; and 21; 45,X and 45,X mosaics; triploidy; other autosomal duplications and/or deletions; and other (than 45,X) sex chromosomal aneuploidies. It is suggested this data could be used to assist pre-procedural counselling of patients after the ultrasound scan in tertiary referral centres for prenatal cytogenetic diagnosis.

Spatial and Temporal Changes in Sedimentary Processes at Proglacial Bear Lake, Devon Island, Nunavut, Canada

Lacustrine sedimentary processes are identified on an intra-annual scale at proglacial Bear Lake, Devon Island. Stage recorders, recording thermistors, sediment traps, and underflow monitoring equipment were deployed during the 1999 melt season. Episodic proximal turbidity currents were measured as positive near-bottom temperature anomalies and currents. The timing of individual positive temperature anomalies was clearly associated with diurnal peaks of discharge into the lake. During the period of 23 to 25 July, continuous underflow occurred, which preceded a large discharge event by about 24 h. Sediment traps placed throughout the lake recorded sediment accumulation rates from 16 June to 4 August. An extremely large precipitation event occurred on 29 June, when coarse, carbonate-rich sediment was deposited in front of a secondary tributary by spatially limited turbidity currents. A niveo-eolian deposit was observed on the lake ice, and sediment traps were deployed under this area. Mass accumulation rates in these traps locally overwhelmed fluvially generated sedimentation. This sediment was dominantly sand, which quickly melted through the lake ice and hastened the date of localized break-up.

A NEW CHANNEL TO SEARCH FOR EXTRA-SOLAR SYSTEMS WITH MULTIPLE PLANETS VIA GRAVITATIONAL MICROLENSING

Gaudi, Naber & Sackett pointed out that if an event is caused by a lens system containing more than two planets, all planets will affect the central region of the magnification pattern, and thus the existence of the multiple planets can be inferred by detecting additionally deformed anomalies from intensive monitoring of high magnification events. Unfortunately, this method has important limitations in identifying the existence of multiple planets and determining their parameters due to the degeneracy of the resulting light curve anomalies from those induced by a single planet and the complexity of multiple planet lensing models. In this paper, we propose a new channel to search for multiple planets via microlensing. The method is based on the fact that the anomalies induced by multiple planets are well approximated by the superposition of those of the single planet systems where the individual planet-primary pairs act as independent lens systems. Then, if the source trajectory passes both of the outer deviation regions induced by the individual planets, one can unambiguously identify the existence of the multiple planets. We illustrate that the probability of successively detecting light curve anomalies induced by two Jovian-mass planets located in the lensing zone through this channel will be substantial. Since the individual anomalies can be well modeled by much simpler single planet lensing models, the proposed method has an important advantage of allowing one to accurately determine the parameters of the individual planets.

Initial mapping and interpretation of lunar crustal magnetic anomalies using Lunar Prospector magnetometer data

Maps of relatively strong crustal magnetic field anomalies detected at low altitudes with the magnetometer instrument on Lunar Prospector are presented. On the lunar nearside, relatively strong anomalies are mapped over the Reiner Gamma Formation on western Oceanus Procellarum and over the Rima Sirsalis rille on the southwestern border of Oceanus Procellarum. The main Rima Sirsalis anomaly does not correlate well with the rille itself but is centered over an Imbrian‐aged smooth plains unit interpreted as primary or secondary basin ejecta. The stronger Reiner Gamma anomalies correlate with the locations of both the main Reiner Gamma albedo marking and its northeastward extension. Both the Rima Sirsalis and the Reiner Gamma anomalies are extended in directions approximately radial to the center of the Imbrium basin. This alignment suggests that Imbrium basin ejecta materials (lying in many cases beneath the visible mare surface) are the sources of the nearside anomalies. If so, then the albedo markings associated with the stronger Reiner Gamma anomalies may be consistent with a model involving magnetic shielding of freshly exposed mare materials from the solar wind ion bombardment. Two regions of extensive magnetic anomalies are mapped in regions centered on the Ingenii basin on the south central farside and near the crater Gerasimovic on the southeastern farside. These regions are approximately antipodal to the Imbrium and Crisium basins, respectively. The Imbrium antipode anomaly group is the most areally extensive on the Moon, while the largest anomaly in the Crisium antipode group is the strongest detected by the Lunar Prospector magnetometer. A consideration of the expected antipodal effects of basin‐forming impacts as well as a combination of sample data and orbital measurements on the nearside leads to the conclusion that the most probable sources of magnetic anomalies in these two regions are ejecta materials from the respective impacts. In both regions the strongest individual anomalies correlate with swirl‐like albedo markings of the Reiner Gamma class visible on available orbital photography.

Global and Regional Sea Surface Temperature Trends

Individual sea surface temperature (SST) anomalies are calculated using a satellite-based climatology and observations from the World Ocean Atlas 1994(WOA94) and the Comprehensive Ocean‐Atmosphere Data Set (COADS) to characterize global and regional changes in ocean surface temperature since 1942. For each of these datasets, anomaly trends are computed using a new method that groups individual anomalies into climatological temperature classes. These temperature class anomaly trends are compared with trends estimated using a technique representative of previous studies based on 58 latitude‐longitude bins. Global linear trends in the data-rich period between 1960 and 1990 calculated from the WOA94 data are found to be 0.14 86 0.048C decade21 for the temperature class approach and 0.13 86 0.048C decade21 for the 58 bin approach. The corresponding results for the COADS data are 0.10 86 0.038C and 0.09 86 0.038C decade21. These trends are not statistically different at the 95% confidence level. Additionally, they agree closely with both SST and land‐air temperature trends estimated from results reported by the Intergovernmental Panel on Climate Change. The similarity between the COADS trends and the trends calculated from the WOA94 dataset provides confirmation of previous SST trend studies, which are based almost exclusively on volunteer observing ship datasets like COADS. Regional linear trends reveal a nonuniformity in the SST rates between 1945‐70 and 1970‐95. Intensified warming during the later period is observed in the eastern equatorial Pacific, the North Atlantic subtropical convergence, and in the vicinity of the Kuroshio extension. Also, despite close agreement globally, localized differences between COADS and WOA94 trends are observed.

Alteration zoning and primary geochemical dispersion at the Bronzewing lode-gold deposit, Western Australia

The Late Archaean Bronzewing lode-gold deposit is in the Yandal greenstone belt, Western Australia. It is located in a 500-m-wide, N–S trending, structural corridor consisting of an anastomosing set of brittle–ductile shear zones and is chiefly hosted by tholeiitic basalts, which are metamorphosed at mid- to upper-greenschist facies. Syn-peak metamorphic alteration surround all ore bodies, and alteration extends laterally for ≤80 m from individual mineralised structures. Individual alteration haloes partially overlap and form a >1.5-km-long and ≤300-m-wide domain. The alteration sequence, studied here at 140 m below the present undisturbed surface, comprises distal calcite–chlorite–albite–quartz, intermediate calcite–dolomite–chlorite–muscovite–albite–quartz and proximal ankerite–dolomite–muscovite–albite–quartz–pyrite zones. Mass transfer calculations indicate that chemical changes during alteration include enrichment of Ag, Au, Ba, Bi, CO2, K, Rb, S, Sb, Te and W, and depletion of Na, Sr and Y. The elements Al, Ca, Cr, Cu, Fe, Mg, Mn, Ni, P, Ti, V, Zn and Zr are immobile. The degree of chemical change increases with proximity to gold ore zones. In addition, abundant quartz veins indicate substantial silica mobility during the hydrothermal event, although there is no large relative silica loss or gain in the host rock. The broadest anomaly surrounding the Bronzewing gold deposit is defined by tellurium (>10 ppb) which, if it is a hydrothermal anomaly, extends beyond the 400 × 600 m study area. Anomalous values for CO2, K, Rb and Sb also define wider zones than does anomalous gold (>4 ppb), although even the lithogeochemical gold anomaly extends across strike for as much as 80 m away from ore and >600 m along the N–S strike of the shear zone corridor. Also carbonation and sericitisation indices outline large exploration targets at the Bronzewing deposit. Sericitisation indices define anomalies that extend for tens of metres beyond visible potassic alteration, whereas the anomalies defined by the carbonation indices do not extend beyond visible carbonation. None of the individual alteration indices or pathfinder elements are able to define consistent gradients towards ore. However, the respective dimensions of individual geochemical anomalies can be used as an extensive, although stepwise, vector towards ore. This sequence is, from species with broadest dispersion first, as follows: Te > CO2/Ca ≥ Sb, 3K/Al, Rb/Ti ≥ Au, W > Y/Ti (depletion) > Ag ≥ Bronzewing ore.

The IMF pile-up regions near the Earth and Venus: lessons for the solar wind - Mars interaction

The Mars Global Surveyor mission has revealed that localized crustal paleomagnetic anomalies are a common feature of the Southern Hemisphere of Mars. The magnetometer measured small-scale magnetic fields associated with many individual magnetic anomalies have magnitudes ranging from hundreds to thousands nT at altitude above 120 km. That makes Mars globally different from both Venus and Earth. The data collected by Lunar Prospector near the Moon were interpreted as evidence that above regions of inferred strong surface magnetic fields on the Moon the SW flow is deflected, and a small-scale mini-magnetosphere exists under some circumstances. With a factor of 100 stronger magnetic fields at Mars and a lower SW dynamic pressure, those conditions offer the opportunity for a larger size of small `magnetospheres' which can be formed by the crustal magnetic fields. Outside the regions of the magnetic anomalies, the SW/Mars interaction is Venus-like. Thus, at Mars the distinguishing feature of the magnetic field pile-up boundary most likely varies from Venus-like to Earth-like above the crustal magnetic field regions. The observational data regarding the IMF pile-up regions near Venus and the Earth are initially reviewed. As long as the SW/Mars interaction remains like that at Venus, the IMF penetrates deep into the Martian ionosphere under the `overpressure' conditions. Results of numerical simulations and theoretical expectations regarding the temporal evolution of the IMF inside the Venus ionosphere and appearance of superthermal electrons are also reviewed and assessed.

Are dental anomalies risk factors for apical root resorption in orthodontic patients?

Regression analyses suggest a weak prediction power of identified risk factors for apical root resorption in orthodontic patients, indicating the presence of etiologic or causative factors that have not yet been disclosed. To investigate the possible significance of dental anomalies as risk factors, pretreatment and posttreatment periapical radiographs of 84 patients with presence of at least one dental anomaly and of 84 patients without such anomalies were compared. The patients in the two groups were matched according to age, gender, Angle Class, extraction therapy, overbite, and treatment time. Apical root resorption was calculated by subtracting posttreatment tooth length measurements from the corresponding pretreatment measurements. Two sample t tests revealed no differences in mean root resorption between the patients in the two groups ( P = .88). Stepwise regression analyses did not identify any of the individual anomalies as risk factors. In addition, patients with more than one anomaly did not appear to be at increased risk. (Am J Orthod Dentofacial Orthop 1999;116:187-95)

Alteration and primary geochemical dispersion associated with the Bulletin lode-gold deposit, Wiluna, Western Australia

The Bulletin lode-gold deposit is within the northernmost part of the Norseman–Wiluna greenstone belt in the Archaean Yilgarn Block, Western Australia. It is located within a brittle–ductile shear zone and hosted by tholeiitic metavolcanic rocks. Syn-metamorphic wallrock alteration envelops the gold mineralisation and is pervasive throughout the entire shear zone and extends up to 150 m into the undeformed wallrocks. Alteration is characterised by the sequence of distal chlorite–calcite, intermediate calcite–dolomite, outer proximal sericite and inner proximal dolomite–sericite zones. The thickness of the alteration envelope, and the occurrence of dolomite in the alteration sequence, can be used as a rough guide to the width, extent and grade of gold mineralisation, because a positive correlation exists between these variables. Mass transfer evaluations indicate that chemical changes related to the wallrock alteration are similar in all host rocks: in general, Ag, As, Au, Ba, CO 2, K, Rb, S, Sb, Te and W are enriched, Na and Y are depleted, and Al, Cr, Cu, Fe, Mg, Mn, Nb, Ni, P, Se, V, Zn and Zr are immobile, while Ca, Si and Sr show only minor or negligible relative changes. The degree of mobility of each component increases with proximity to gold mineralisation. The largest potential exploration targets are possibly defined by regional As (>6 ppm) and Sb (>0.6 ppm) anomalies. These anomalies, if real, extend laterally for >150 m from the mineralised shear zone into areas of apparently unaltered rocks. Anomalies defined by Te (>10 ppb), W (>0.6 ppm), carbonation indices, local enrichment of Sb (>2.0 ppm) and As (>28 ppm), and potassic alteration indices also form significant exploration targets extending beyond the HJB shear zone and the Au anomaly (>6 ppb) and, locally, into apparently unaltered rock. Gold, itself, has a restricted dispersion, with an anomaly extending for 1–35 m from ore, and being restricted to within the shear zone itself. Amongst individual geochemical parameters, only As and Sb define significant, consistent and smooth trends (vectors) when laterally approaching the ore. However, the respective dimensions of individual geochemical anomalies can be used as an extensive, though stepwise, vector towards ore.

Prevention of alcohol abuse-related birth effects--I. Public education efforts.

Maternal alcohol abuse during pregnancy can result in a pattern of anomalies in children called 'fetal alcohol syndrome' (FAS) and more recently, 'fetal alcohol abuse syndrome (FAAS)'. FAAS as well as individual alcohol-related anomalies, called 'alcohol abuse-related birth effects' (AARBEs), are widely considered to be totally preventable, because they stem from a behaviour that is presumably modifiable. However, current strategies to reduce their occurrence are more palliative than preventive, because their underlying premise, viz. that raising public awareness of the potential dangers of commonly used substances such as alcohol is enough to reduce their use, lacks empirical support. Moreover, in some cases they are also counter-productive. After considering the relevant literature, this review contends that 'universal' public education efforts will only be effective in reducing FAAS and AARBEs if they focus on the cause of these disorders, which is alcohol abuse rather than the currently open-ended message that any amount of alcohol consumption during pregnancy constitutes a danger to an unborn child. This argument lays the ground work for an alternative and more pragmatic strategy set forth in the following paper for preventing FAAS and AARBEs.

Warm Pool SST Variability in Relation to the Surface Energy Balance

The warm tropical oceans underlie the most convective regions on earth and are a critical component of the earth’s climate, yet there are differing opinions on the processes that control warm pool SST. The Indo‐Pacific warm pool is characterized by large-scale variations in SST approaching 308C on intraseasonal timescales. In this study, surface heat flux anomalies associated with composite warm episodes over three spatial scales in both the Pacific and Indian Ocean basins are examined. The current study benefits from the recently available National Centers for Environmental Prediction‐National Center for Atmospheric Research reanalysis dataset that enables the examination of variability in surface evaporation with moderate confidence. Solar flux estimates from the reanalysis are somewhat less reliable than evaporation estimates, however, and two techniques that infer surface shortwave radiation from satellite retrievals of cloud properties are considered. Error in all measurements is quantified. Both shortwave and evaporative flux variability play significant roles in modifying the temperature of the warm pool, though the relative importance of individual flux anomalies depends on SST tendency and geographical location. There also exist differences in the relative heating roles of the flux anomalies among episodes within a fixed location, though in instances the resolved differences are less than likely flux estimation error. Differences also exist between the ocean basins. A more pronounced annual cycle exists in the eastern Indian Ocean, and SST there is less sensitive to surface thermal forcing. Finally, the analysis offers evidence that SST is not regulated by a simple atmospheric thermodynamic response to the surface. Instead, the relationship between warm pool variability and large-scale dynamical features of the Tropics (e.g., intraseasonal oscillation and the seasonal monsoon) is demonstrated. The conclusions are shown to be robust to spatial scale and are consistent with a recent analysis of Tropical Oceans and Global Atmosphere Coupled Ocean‐Atmosphere Response Experiment observations.

Spiral computed tomography scanning after intravenous infusion cholangiography for biliary duct anomalies

Iatrogenic injury of the bile duct during cholecystectomy represents a failure of surgical technique, especially for laparoscopic surgery. Knowledge of the patient's individual ductal anatomy and anomalies preoperatively would be helpful in avoiding such injuries. Therefore, we investigated the anatomy of the biliary duct and any anomalies using spiral computed tomography (SCT) scanning following intravenous infusion cholangiography (IVC-SCT). Laparoscopic cholecystectomies (LC) were attempted on 437 patients at the Kansai Medical University. Preoperative IVC-SCT and laparoscopic cholangiography were attempted in all of the patients. An overall anomalous union of the cystic duct was seen in 71 (16.2%) out of the 437 patients subjected to IVC-SCT. The following anomalies were observed: right hepatic duct entry in 7 cases (1.6%), parallel low entry in 17 cases (3.9%), posterior spiral entry in 35 cases (8.0%), anterior spiral entry in 7 cases (1.6%), and accessory duct entry in 5 cases (1.1%). The success rate for the LC was 99.5% (435/437). Three patients were switched to open surgery owing to advanced gallbladder cancer and severe adhesions. The success rate for the laparoscopic cholangiography was 97.2% (423 of 435). Intraoperative right hepatic duct injury occurred in only 1 patient with a bile duct anomaly, and it was repaired with laparoscopic T-tube drainage. The preoperative examination of the biliary tract by IVC-SCT was technically simple, less invasive, and may helpful in avoiding damage to the bile duct, especially in patients with biliary duct anomalies.

Real Estate Investment Trusts and Calendar Anomalies

There have been numerous studies in the finance literature on the existence of calendar anomalies in common stocks and a few studies of individual anomalies in the markets for real estate investment trusts. This study provides a comprehensive examination of the existence of four calendar anomalies for REITs and common stocks from 1986 through 1993. The results show the existence of the January effect, the turn-of-the-month effect, the day-of-the-week effect, and the pre-holiday effect in REITs and an equally weighted index of stocks. REIT returns tend to be higher in January, on Friday, on turn-of-the-month trading days, and on pre-holiday trading days.

Large-Scale Antecedent Conditions Associated with the 12–14 March 1993 Cyclone (“Superstorm '93”) over Eastern North America

The results of a multiscale analysis of the 12–14 March 1993 superstonn (SS93) over eastern North America are presented. A time sequence of overlapping 10-day time-mean 5OO-hPa geopotential height and anomaly composites shows that the Northern Hemisphere (NH) flow pattern from 18 February to 15 March 1993 is characterized by 1) three persistent troughs situated over eastern Asia and the northwestern Pacific, over eastern North America, and over northwestern Africa and southwestern Europe eastward to central Russia; and 2) a massive blocking anticyclone located over the central and eastern Atlantic. Beginning 8–9 March 1993 the planetary-scale flow amplifies substantially. The explosive SS93 cyclogenesis and the transport of cold air to very low latitudes occurs a few days later as the NH available potential energy content, after peaking on 9 March 1993, decreases by about 6%–7%. A dynamical tropopause analysis is used to track coherent transient potential vorticity (PV) anomalies and show their qualitative interaction with the planetary-scale flow. SS93 is attributed to the interaction and eventual merger of strong PV anomalies embedded in the northern and southern branches of the westerlies in a background confluent northwesterly flow associated with an amplifying positive-phase Pacific–North American flow pattern. The northern PV anomaly originates in southwestern Canada on 18 February and circumnavigates the NH at relatively high latitudes, a track that permits it to maintain arctic characteristics prior to merger. The southern PV anomalies, tracked from Europe and western Asia eastward across the Pacific, reach North America by 11 March 1993 where they become associated with widespread convention over southern Texas and the northwestern Gulf of Mexico beginning 12 March 1993. The unique aspects of SS93 are attributed to 1) the near simultaneous amplification of the planetary-scale flow and the lateral and vertical interaction of individual PV anomalies cast of the Rockies during the merger process, and 2) the lag of the northern PV anomaly relative to the southern anomaly so that a baroclinic zone containing lower-tropospheric air of significant conditional instability is allowed to remain in place over southern Texas and the northwest Gulf of Mexico in the cyclogenetic environment ahead of the northern PV anomaly.