Repeat Observations Research Articles

A SPECTROSCOPIC SURVEY OF THE FIELDS OF 28 STRONG GRAVITATIONAL LENSES

We present the spectroscopic redshift catalog from a wide-field survey of the fields of 28 galaxy-mass strong gravitational lenses. We discuss the acquisition and reduction of the survey data, collected over 40 nights of 6.5m MMT and Magellan time, employing four different multi-object spectrographs. We determine that no biases are introduced by combining datasets obtained with different instrument/spectrograph combinations. Special care is taken to determine redshift uncertainties using repeat observations. The redshift catalog consists of 9768 new and unique galaxy redshifts. 82.4% of the catalog redshifts are between z=0.1 and z=0.7, and the catalog median redshift is z=0.36. The data from this survey will be used to study the lens environments and line-of-sight structures to gain a better understanding of the effects of large scale structure on lens statistics and lens-derived parameters.

Terrain parameters of glide snow avalanches and a simple spatial glide snow avalanche model

Glide snow avalanches are dangerous and difficult to predict. Despite substantial recent research there is still inadequate understanding regarding the controls of glide snow avalanche release. Glide snow avalanches often occur in similar terrain or the same locations annually, and repeat observations and prior work suggest that specific topography may be critical. Thus, to gain a better understanding of the terrain component of these types of avalanches we examined terrain parameters associated with the specific area of glide snow avalanche release in comparison to avalanche starting zones where no glide snow avalanches were observed (i.e. non-glide snow avalanche terrain).Glide snow avalanche occurrences visible from the Going-to-the-Sun Road corridor in Glacier National Park, Montana from 2003 to 2013 are investigated using a database of all avalanche occurrences derived of daily observations each year from 1 April to 1 June. This yielded 192 glide snow avalanches in 53 distinct avalanche paths. Each avalanche was digitized in a GIS using satellite, oblique, and aerial imagery as reference. A set of 117 non-glide snow avalanche starting zones were also selected in this manner. These were start zones with avalanche activity potential, but without glide avalanches observed. Topographical parameters such as area, slope, aspect, curvature, potential incoming solar radiation, distance from ridge, and elevation were then derived for the entire dataset utilizing tools with a GIS and a 10m DEM. Ground class and a glide factor were calculated using a four level classification index with in-situ observations and a land surface type layer in a GIS.A total of 21 terrain variables were examined using a univariate analysis between areas where glide snow avalanches occurred and areas where glide snow avalanches were never observed, despite crack formation. Only two variables were not significantly different. The significantly different variables were then used to train a classification tree to distinguish between glide and non-glide snow avalanche terrain. A 10-fold cross validated tree resulted in four decision nodes to classify the data. The nodes split on glide factor, maximum slope angle, seasonal sum of incoming solar radiation, and maximum curvature to distinguish between glide snow avalanche and non-glide snow avalanche terrain with an unweighted average accuracy (RPC) of 0.95 and probability of detection of events (POD) of 0.99.Finally, the results of the cross-validated tree were used in a GIS to examine other areas, not used in the training dataset of the classification tree, of potential glide snow avalanche release within Glacier National Park. Using this understanding of the role of topographic parameters on glide snow avalanche activity, a spatial terrain based model was developed to identify other areas with high glide snow avalanche potential outside of the immediate observation area. This simple spatial model correctly classified 78percent of actual glide snow avalanche terrain (pixel count) of a small test area of four independent observed glide snow avalanches.

Reliable inference of light curve parameters in the presence of systematics

AbstractTime-series photometry and spectroscopy of transiting exoplanets allow us to study their atmospheres. Unfortunately, the required precision to extract atmospheric information surpasses the design specifications of most general purpose instrumentation. This results in instrumental systematics in the light curves that are typically larger than the target precision. Systematics must therefore be modelled, leaving the inference of light-curve parameters conditioned on the subjective choice of systematics models and model-selection criteria. Here, I briefly review the use of systematics models commonly used for transmission and emission spectroscopy, including model selection, marginalisation over models, and stochastic processes. These form a hierarchy of models with increasing degree of objectivity. I argue that marginalisation over many systematics models is a minimal requirement for robust inference. Stochastic models provide even more flexibility and objectivity, and therefore produce the most reliable results. However, no systematics models are perfect, and the best strategy is to compare multiple methods and repeat observations where possible.

The Kepler field of view covered with the LAMOST spectroscopic observations

AbstractThe Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) at the Xinglong observatory in China is a 4-m telescope equipped with 4,000 optical fibres. In 2010, we initiated the LAMOST-Kepler project which aimed at collecting low-resolution spectra of stars from the Kepler Input Catalog covering uniformly the Kepler field of view. The first round of the LAMOST-Kepler project has been completed in September 2014 resulting in more than 100,000 low-resolution spectra. We used those data to derive the effective temperature, the surface gravity, and the mean metallicity of our targets, as well as to detect fast rotators, and to identify emission-line stars. Our results are consistent with those reported in the literature and derived from high-resolution spectroscopy. The second round of the LAMOST-Kepler project will allow to improve the coverage of the Kepler field and to repeat observations of selected targets.

Turning off the lights

Decades-long repeat observations of supernova 1987A offer us unique, real-time insights into the violent death of a massive star and its long-term environmental effects, until its eventual switch-off.

Multiscale Analysis of River Networks using the R Package linbin

AbstractAnalytical tools are needed in riverine science and management to bridge the gap between GIS and statistical packages that were not designed for the directional and dendritic structure of streams. We introduce linbin, an R package developed for the analysis of riverscapes at multiple scales. With this software, riverine data on aquatic habitat and species distribution can be scaled and plotted automatically with respect to their position in the stream network or—in the case of temporal data—their position in time. The linbin package aggregates data into bins of different sizes as specified by the user. We provide case studies illustrating the use of the software for (1) exploring patterns at different scales by aggregating variables at a range of bin sizes, (2) comparing repeat observations by aggregating surveys into bins of common coverage, and (3) tailoring analysis to data with custom bin designs. Furthermore, we demonstrate the utility of linbin for summarizing patterns throughout an entire stream network, and we analyze the diel and seasonal movements of tagged fish past a stationary receiver to illustrate how linbin can be used with temporal data. In short, linbin enables more rapid analysis of complex data sets by fisheries managers and stream ecologists and can reveal underlying spatial and temporal patterns of fish distribution and habitat throughout a riverscape.Received November 13, 2014; accepted April 14, 2015

DISCOVERY OF EIGHTz∼ 6 QUASARS IN THE SLOAN DIGITAL SKY SURVEY OVERLAP REGIONS

We present the discovery of eight quasars at z~6 identified in the Sloan Digital Sky Survey (SDSS) overlap regions. Individual SDSS imaging runs have some overlap with each other, leading to repeat observations over an area spanning >4000 deg^2 (more than 1/4 of the total footprint). These overlap regions provide a unique dataset that allows us to select high-redshift quasars more than 0.5 mag fainter in the z band than those found with the SDSS single-epoch data. Our quasar candidates were first selected as i-band dropout objects in the SDSS imaging database. We then carried out a series of follow-up observations in the optical and near-IR to improve photometry, remove contaminants, and identify quasars. The eight quasars reported here were discovered in a pilot study utilizing the overlap regions at high galactic latitude (|b|>30 deg). These quasars span a redshift range of 5.86<z<6.06 and a flux range of 19.3<z_AB<20.6 mag. Five of them are fainter than z_AB=20 mag, the typical magnitude limit of z~6 quasars used for the SDSS single-epoch images. In addition, we recover eight previously known quasars at z~6 that are located in the overlap regions. These results validate our procedure for selecting quasar candidates from the overlap regions and confirming them with follow-up observations, and provide guidance to a future systematic survey over all SDSS imaging regions with repeat observations.

Abstract 141: Predictors of the Utilization of QT Interval Lengthening Medications in the Atherosclerosis Risk in Communities (ARIC) Study

Objective: Prolongation of corrected QT interval (QTc) is associated with increased morbidity and mortality. We examined the predictors of the use of QTc prolonging medications (QTPM). Methods: We included 15,792 ARIC participants with a resting, standard 12-lead electrocardiogram and ≥ 1 measure of QTc over up to four triennial examinations between 1987 and 1998 (54,638 person-visits). Participants with missing data were excluded (n=1,668). To optimize clinical applicability, QTc was calculated using Bazett’s equation. At each visit, we identified participants using ≥ 1 CredibleMeds classified QTPMs, age &gt; 65 years, females, and those with LVH, or QTc &gt; 500 ms at the prior visit. We used linear regression (random and fixed effects models) for 37,233 person-visit observations from visits 2-4 to determine predictors of the use of QTPMs. The following known risk factors and potential predictors for QTc lengthening were assessed: age, female sex, LVH, and QTc at the prior visit. Standard errors were corrected for repeat observations per person. Additional risk factors will be assessed in future analyses. Results: Among person-visit observations from Visit 2-4 (mean age 59.7, 55% female, 9% LVH, mean QTc 431), 16% (n= 5,153) of participants were using one or more QTPM. Preliminary results suggest three of the four identified risk factors predicted use of QTPMs: age, sex, and QTc at prior visit. Prolonged QTc at prior visit was associated with a lower probability of using QTPM. In contrast, use of QTPMs was positively associated with a joint effect of age and female sex. The latter is concerning given older females are at increased risk for QTc prolongation. Conclusions: In this preliminary analysis, several predictors of QTPM use emerged. Future analyses will include additional predictors and assessment of outcome will adjust for these predictors.

Bayesian analysis of resolved stellar spectra: application to MMT/Hectochelle observations of the Draco dwarf spheroidal

We introduce a Bayesian method for fitting faint, resolved stellar spectra in order to obtain simultaneous estimates of redshift and stellar-atmospheric parameters. We apply the method to thousands of spectra---covering 5160-5280 Angs. at resolution R~20,000---that we have acquired with the MMT/Hectochelle fibre spectrograph for red-giant and horizontal branch candidates along the line of sight to the Milky Way's dwarf spheroidal satellite in Draco. The observed stars subtend an area of ~4 deg^2, extending ~3 times beyond Draco's nominal `tidal' radius. For each spectrum we tabulate the first four moments---central value, variance, skewness and kurtosis---of posterior probability distribution functions representing estimates of the following physical parameters: line-of-sight velocity v_los, effective temperature (T_eff), surface gravity (logg) and metallicity ([Fe/H]). After rejecting low-quality measurements, we retain a new sample consisting of 2813 independent observations of 1565 unique stars, including 1879 observations for 631 stars with (as many as 13) repeat observations. Parameter estimates have median random errors of sigma_{v_los}=0.88 km/s, sigma_{T_eff}=162 K, sigma_logg=0.37 dex and sigma_[Fe/H]=0.20 dex. Our estimates of physical parameters distinguish ~470 likely Draco members from interlopers in the Galactic foreground.

Split-beam echo sounder observations of natural methane seep variability in the northern Gulf of Mexico

A method for positioning and characterizing plumes of bubbles from marine gas seeps using an 18 kHz scientific split-beam echo sounder (SBES) was developed and applied to acoustic observations of plumes of presumed methane gas bubbles originating at approximately 1400 m depth in the northern Gulf of Mexico. A total of 161 plume observations from 27 repeat surveys were grouped by proximity into 35 clusters of gas vent positions on the seafloor. Profiles of acoustic target strength per vertical meter of plume height were calculated with compensation for both the SBES beam pattern and the geometry of plume ensonification. These profiles were used as indicators of the relative fluxes and fates of gas bubbles acoustically observable at 18 kHz and showed significant variability between repeat observations at time intervals of 1 h–7.5 months. Active gas venting was observed during approximately one third of the survey passes at each cluster. While gas flux is not estimated directly in this study owing to lack of bubble size distribution data, repeat surveys at active seep sites showed variations in acoustic response that suggest relative changes in gas flux of up to 1 order of magnitude over time scales of hours. The minimum depths of acoustic plume observations at 18 kHz averaged 875 m and frequently coincided with increased amplitudes of acoustic returns in layers of biological scatterers, suggesting acoustic masking of the gas bubble plumes in these layers. Minimum plume depth estimates were limited by the SBES field of view in only five instances.

Abstract 13786: Contribution of Medications and Risk Factors to QT Interval Lengthening in the Atherosclerosis Risk in Communities (ARIC) Study

Objective: Prolongation of corrected QT interval (QTc) is associated with increased morbidity and mortality, but the association between the number of QT interval prolonging medications (QTPMs) versus selected non-pharmacologic risk factors on the magnitude of QTc lengthening is unknown. We examined these associations in a longitudinal study of a population-based cohort. Methods: We included 15,792 ARIC participants with a resting, standard 12-lead electrocardiogram and ≥ 1 measure of QTc over up to four triennial examinations between 1987 and 1998 (54,638 person-visits). Participants with QRS &gt; 120 ms were excluded (n=2,333). To optimize clinical applicability, QTc was calculated using Bazett’s equation. At each visit, we identified participants using ≥ 1 AzCERT-classified QTPMs, age &gt; 65 years, females, and those with left ventricular hypertrophy (LVH), or QTc &gt; 500 ms at the prior visit. We used linear regression for 36,513 person-visit observations from visits 2-4 to examine QTc lengthening associations. Visit indicators were controlled for time, and standard errors were corrected for repeat observations per person. Results: Use of any QTPM increased from 9% to 17% between visits 1 and 4 and occurred more frequently among females and participants with LVH. Among person-visit observations from Visit 2-4, 70% (n=25,513) had at least one risk factor including age &gt; 65 years (25%), female sex (56%), LVH (8%) and QTc&gt;500 ms (1%). In patients receiving no QTPM, female sex was associated with the greatest QTc lengthening at 13 ms [95% CI 12-13] followed by LVH at 7 ms [6-9], QTc &gt; 500 ms at 7 [4-10], and age &gt; 65 at 2 ms [1-3]. Mean QTc increased with increasing number of QTPMs and risk factors (Table). The greatest QTc lengthening occurred in participants using ≥ 2 medications with ≥ 1 risk factor. Conclusions: Risk factors, particularly female sex, contribute more to QTc lengthening than QTPMs.

The effect of glycemic control on CEA, CA 19-9, amylase and lipase levels.

BackgroundDiabetes mellitus is closely related to pancreas cancer. In this study we aimed to investigate the effect of hyperglycemia on tumor and inflammation markers, as well as pancreatic exocrine functions.MethodsA total of 98 consecutive diabetic patients with poor glycemic control, and 50 healthy controls were included in the study. We measured hsCRP, erythrocyte sedimentation rate (ESR), CA19-9, CEA, amylase and lipase in addition to routine biochemistry tests, before and after euglycemia was achieved.ResultsFasting blood glucose, HbA1c, CA19-9, CEA, hsCRP, ESR, triglycerides, AST, ALT, GGT, ALP, total cholesterol and LDL-C levels decreased significantly with the regulation of glycemic control. Amylase and lipase levels increased with the regulation of glycemic control. After glycemic control, CA19-9 and CEA levels were still higher, whereas amylase and lipase levels were still lower in the diabetic group compared with the control group. Basal HbA1c showed significant correlation with CA19-9, CEA, amylase and lipase.ConclusionsWe propose to repeat observations of tumor markers after hyperglycemia is resolved, in order to avoid unnecessary invasive tests. Our data also suggest that pancreatic exocrine function was improved with lowering blood glucose in a short period of time.

The role of performance measurement models in multi level alignment

Purpose – Market deregulation in the utilities sector has led to increased competition and rising customer expectations in both established and new markets. This, in turn, has forced organisations such as electricity and telecoms to make rapid, enterprise-wide changes on an increasingly frequent basis which in turn has led to problems with alignment. Misalignment can occur at many levels and can result in misused resources, loss of competitiveness, excessive cycle times, higher costs and loss of agility. The purpose of this paper is twofold. Given the lack of overarching theory, the paper begins by borrowing from contingency, dynamic capability and organisational learning constructs, to explore the role that performance measurement models can bring to improve the alignment between business strategy and functional strategy (level 1 alignment). Second, the paper analyses the role of performance measurement models in developing functional practices aligned with supply chain management (SCM) strategies (level 2 alignment). Design/methodology/approach – The study adopts an exploratory theory-building approach using four case studies. These are used as key supply chains in both established and new business areas within two longitudinal university-industry research partnerships (each of three years duration). Data from repeat interviews (n=42), focus groups (n=10), documentation and observations is analysed and forms the basis for the development of a conceptual framework and a set of related propositions. The data analysis followed Radnor and Boaden's (2004) method for analysing interpretive research. Findings – The findings show the role and impact of performance measurement models and methods on alignment at two levels, i.e. level 1 alignment – between business strategy and functional (SCM) strategy, and level 2 alignment – between the functional strategy (SCM) and SCM routines and practices. Originality/value – To date, there are few studies which explore the development of theory and practice in relation to the role and impact of performance measurement models and methods in improving organisational alignment. This exploratory theory building study makes a contribution to this gap through the development of the conceptual framework and propositions.

Detecting small gravity change in field measurement: simulations and experiments of the superconducting gravimeter—iGrav

In order to detect small gravity changes in field measurements, such as with CO2 storage, we designed simulations and experiments to validate the capabilities of the iGrav superconducting gravimeter. Qualified data processing was important to obtain the residual gravity from the iGrav's raw gravity signals, without the tidal components, atmosphere, polar motion and hydrological effects. Two simulations and four designed experiments are presented in this study. The first simulation detected the gravity change during CO2 injection. The residual gravity of CO2 leakage was targeted with the second simulation from the main storage reservoir to secondary space underground. The designed experiments monitored the situation of gravity anomalies in the iGrav's records. These tests focused on short-term gravity anomalies, such as gravity changes, step functions, repeat observations and gradient measurements from the iGrav, rather than on long-term tidal effects. The four laboratory experiments detected a decrease in gravity of −0.56 ± 0.15 µGal (10−8 m s−2) with a 92.8 kg weight on the top of the iGrav. A step function occurred in the gravity signals, when the tilt control was out of balance. We also used a professional camera dolly with a track to observe repeated horizontal movements and an electric lift table for controlled vertical movements to measure the average gradient of −2.67 ± 0.01 µGal cm−1.

Bringing an ecological view of change to Landsat‐based remote sensing

When characterizing the processes that shape ecosystems, ecologists increasingly use the unique perspective offered by repeat observations of remotely sensed imagery. However, the concept of change embodied in much of the traditional remote‐sensing literature was primarily limited to capturing large or extreme changes occurring in natural systems, omitting many more subtle processes of interest to ecologists. Recent technical advances have led to a fundamental shift toward an ecological view of change. Although this conceptual shift began with coarser‐scale global imagery, it has now reached users of Landsat imagery, since these datasets have temporal and spatial characteristics appropriate to many ecological questions. We argue that this ecologically relevant perspective of change allows the novel characterization of important dynamic processes, including disturbances, long‐term trends, cyclical functions, and feedbacks, and that these improvements are already facilitating our understanding of critical driving forces, such as climate change, ecological interactions, and economic pressures.

Long-term monitoring of martian gully formation and evolution with MRO/HiRISE

Gully landforms are commonly taken as evidence for surface liquid water in the recent geological history of Mars. Repeat observations with the High Resolution Imaging Science Experiment (HiRISE) instrument on the Mars Reconnaissance Orbiter demonstrate widespread activity in gullies in the southern hemisphere, particularly in those with the freshest morphologies. This activity includes substantial channel incision and large-scale mass movements, and constitutes ongoing gully formation rather than degradation of older landforms. New apron deposits that are bright, dark and neutrally toned have all been observed. The timing of gully activity is seasonally controlled and occurs during the period when seasonal frost is present and defrosting. These observations support a model in which currently active gully formation is driven mainly by seasonal CO2 frost. Gullies in the northern hemisphere are far less active than those in the south. This may be due to the current timing of perihelion near the northern winter solstice. Integrated over time, activity like that observed within the past few years appears capable of forming all of the martian gully landforms on timescales of millions of years. Additionally, the current style and rate of activity is able to erase meter- to decameter-scale surface features that might have been uniquely produced by other processes during the last obliquity high ∼0.4Ma. Although it is impossible to rule out a past role for water in the formation of martian gullies, a model in which gullies form only through currently active processes with little or no liquid water is consistent with our observations.

Galaxy And Mass Assembly (GAMA): AUTOZ spectral redshift measurements, confidence and errors

The Galaxy And Mass Assembly (GAMA) survey has obtained spectra of over 230000 targets using the Anglo-Australian Telescope. To homogenise the redshift measurements and improve the reliability, a fully automatic redshift code was developed (autoz). The measurements were made using a cross-correlation method for both absorption-line and emission-line spectra. Large deviations in the high-pass filtered spectra are partially clipped in order to be robust against uncorrected artefacts and to reduce the weight given to single-line matches. A single figure of merit (FOM) was developed that puts all template matches onto a similar confidence scale. The redshift confidence as a function of the FOM was fitted with a tanh function using a maximum likelihood method applied to repeat observations of targets. The method could be adapted to provide robust automatic redshifts for other large galaxy redshift surveys. For the GAMA survey, there was a substantial improvement in the reliability of assigned redshifts and in the lowering of redshift uncertainties with a median velocity uncertainty of 33 km/s.

Dynamic Association of Mortality Hazard with Body Shape

BackgroundA Body Shape Index (ABSI) had been derived from a study of the United States National Health and Nutrition Examination Survey (NHANES) 1999–2004 mortality data to quantify the risk associated with abdominal obesity (as indicated by a wide waist relative to height and body mass index). A national survey with longer follow-up, the British Health and Lifestyle Survey (HALS), provides another opportunity to assess the predictive power for mortality of ABSI. HALS also includes repeat observations, allowing estimation of the implications of changes in ABSI.Methods and FindingsWe evaluate ABSI z score relative to population normals as a predictor of all-cause mortality over 24 years of follow-up to HALS. We found that ABSI is a strong indicator of mortality hazard in this population, with death rates increasing by a factor of 1.13 (95% confidence interval, 1.09–1.16) per standard deviation increase in ABSI and a hazard ratio of 1.61 (1.40–1.86) for those with ABSI in the top 20% of the population compared to those with ABSI in the bottom 20%. Using the NHANES normals to compute ABSI z scores gave similar results to using z scores derived specifically from the HALS sample. ABSI outperformed as a predictor of mortality hazard other measures of abdominal obesity such as waist circumference, waist to height ratio, and waist to hip ratio. Moreover, it was a consistent predictor of mortality hazard over at least 20 years of follow-up. Change in ABSI between two HALS examinations 7 years apart also predicted mortality hazard: individuals with a given initial ABSI who had rising ABSI were at greater risk than those with falling ABSI.ConclusionsABSI is a readily computed dynamic indicator of health whose correlation with lifestyle and with other risk factors and health outcomes warrants further investigation.

Impact of Objectively Assessing Surgeons’ Teaching on Effective Perioperative Instructional Behaviors

Advancing surgical technology and decreasing resident learning hours have limited exposure to perioperative training, necessitating more effective and efficient perioperative teaching by faculty surgeons. Participation in collaborative efforts and process improvement can change behaviors and enhance teaching. To promote deliberate teaching of residents, change resident perception of their teachers, and produce sustainable improvements by objectively measuring surgeons' perioperative teaching performance. This 3-phase observational study of surgeons' perioperative teaching behaviors included university-based surgeons, general surgery residents, and preclinical student observers and involved elective cases at a 600+ bed tertiary hospital. Initially, we measured teaching behaviors by surgeons unaware of study objectives, provided aggregate and confidential individual feedback, and developed standardized preoperative briefings and postoperative debriefings. Phase 2 applied a deliberate teaching model and reinforced behaviors with continuous process improvement efforts (Plan, Do, Check, Act) and repeat observations. Phase 3 used resident prompts to enhance teaching behaviors and demonstrate sustainability. Resident surveys conducted 3 times assessed perceptions of deliberate guidance by faculty when compared with national benchmarks. Introduction of deliberate faculty preprocedural focusing and postprocedural reinforcement to facilitate resident learning. More frequent and complete perioperative teaching by faculty and the perception of enhanced teaching by residents. Faculty more commonly and more completely performed the 10-step preoperative briefings and postoperative debriefings (P < .001) during phase 2 (250% improvement over baseline). Intraoperative teaching styles significantly improved and residents' survey-reported assessments of faculty teaching improved over national data for describing procedural steps (P = .02) and requests for resident self-evaluation (P = .006). Objective recording of teaching behavior frequency motivated adoption of deliberate guided teaching behaviors by surgeons, resulting in both subjective reports by residents of more frequent teaching and objective recording of parallel improvements. A deliberate focus on objectively assessing surgeon educators' periprocedural teaching may motivate improved teaching.

Narrow absorption line variability in repeat quasar observations from the Sloan Digital Sky Survey

We present the results from a time domain study of absorption lines detected in quasar spectra with repeat observations from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7). Beginning with over 4500 unique time separation baselines of various absorption line species identified in the SDSS DR7 quasar spectra, we create a catalogue of 2522 quasar absorption line systems with two to eight repeat observations, representing the largest collection of unbiased and homogeneous multi-epoch absorption systems ever published. To investigate these systems for time variability of narrow absorption lines, we refine this sample based on the reliability of the system detection, the proximity of pixels with bright sky contamination to individual absorption lines, and the quality of the continuum fit. Variability measurements of this sub-sample based on the absorption line equivalent widths yield a total of 33 systems with indications of significantly variable absorption strengths on time-scales ranging from one day to several years in the rest frame of the absorption system. Of these, at least 10 are from a class known as intervening absorption systems caused by foreground galaxies along the line of sight to the background quasar. This is the first evidence of possible absorption line variability detected in intervening systems, and their short time-scale variations suggest that small-scale structures (~10-100 au) are likely to exist in their host foreground galaxies.