Hydrophone VSP imaging at a shallow site

Geophysics ◽  
1997 ◽  
Vol 62 (3) ◽  
pp. 842-852 ◽  
Author(s):  
Paul A. Milligan ◽  
James W. Rector ◽  
Robert W. Bainer
Keyword(s):  
Primary Source ◽  
Acquisition Time ◽  
Coherent Noise ◽  
Cross Sectional ◽  
Reflection Data ◽  
Shallow Site ◽  
Vsp Data ◽  
Mapping Techniques ◽  
Tube Wave ◽  
Hydrophone Array

We evaluated the capabilities of vertical seismic profiling (VSP) for imaging the complex heterogeneous unconsolidated sedimentary structures at a shallow site. We deployed a 24‐level hydrophone array with 0.5-m level spacing down a preexisting poly vinyl chloride (PVC) cased well. Data acquisition time was quick. Only 15 multioffset shot points using a hammer‐on‐plate source were needed to acquire reflection data between the water table at 3 m and the bedrock at 35 m to produce a depth section image. This image extended 9 m from the receiver well, yielding resolutions between fresh‐water‐bearing sands and impermeable muds and clays of better than 1 m. Depth accuracy of the image was confirmed by good correlation with cone penetrometer logs. We used conventional wavefield separation and VSP-CDP mapping techniques to image the data. Tube waves, created by seismic arrivals at cross‐sectional area changes in the borehole fluid column, were the primary source of coherent noise in the data. The tube‐wave arrival structure was complicated by the hydrophone array, which generated and scattered tube waves at each hydrophone pod. To combat the tube wave interference, we inserted closed‐cell‐foam baffles between elements. The baffles attenuated and slowed the tube waves, and reduced generation and scattering. A comparison between unbaffled and baffled VSP data showed that baffling increased the maximum useful frequency from 300 Hz to over 900 Hz. By contrast, surface shot data recorded at the same site, using buried 40-Hz vertical geophones, exhibited useful frequencies of less than 250 Hz. In addition, coherent noise in surface shot records caused by air waves and first arrivals made it very difficult to identify shallow reflections above 25 m. Reflections from depths as shallow as 10 m were easy to identify in the baffled VSP data.

A hydrophone vertical seismic profiling experiment

Geophysics ◽  
1988 ◽  
Vol 53 (11) ◽  
pp. 1437-1444 ◽  
Author(s):  
Thomas L. Marzetta ◽  
Marion Orton ◽  
Alfred Krampe ◽  
Lucian K. Johnston ◽  
Paul C. Wuenschel
Keyword(s):  
Body Wave ◽  
Vertical Array ◽  
Pressure Signal ◽  
Vertical Seismic Profiling ◽  
Vsp Data ◽  
First Arrival ◽  
Tube Wave ◽  
The Cost ◽  
Velocity Filtering ◽  
Hydrophone Array

To reduce the cost of VSP data acquisition, it is necessary to record the VSP signal from a vertical array of geophones for a single operation of the source. Until a vertical array of clamped three‐component geophones is available, it seems logical to evaluate the capabilities of a vertical array of hydrophones, which is much easier to fabricate. It is well known that elastic waves in the solid couple to pressure waves in the borehole fluid. It is also well known that this coupling excites in the borehole fluid energy known as tube‐wave noise that dominates the borehole pressure signal after the first arrival. (The borehole acts as a waveguide.) In this paper we test the effectiveness of velocity filtering of the borehole pressure signal to attenuate the slowly propagating tube‐wave noise and enhance the faster propagating body‐wave signals. Our initial test satisfactorily extracted from the hydrophone array data a strong reflected event that was also observed in the conventional clamped geophone VSP taken in the same borehole. We were not as successful in recovering subsequent weaker reflected signals from the hydrophone data, because of the strong incoherent ambient tube‐wave noise. This incoherency resulted from instrumental limitations that allowed us to record, for each shot, only three of the twelve hydrophone channels available in the vertical array.

Nutrient supplementation among pregnant women in China: an observational study

2021 ◽  
pp. 1-19
Author(s):  
Tao Han ◽  
Jingwen Dong ◽  
Jiangtao Zhang ◽  
Chenxiao Zhang ◽  
Yuxuan Wang ◽  
...  
Keyword(s):  
Vitamin D ◽  
Folic Acid ◽  
Pregnant Women ◽  
Family Members ◽  
Primary Source ◽  
Cross Sectional Study ◽  
Cross Sectional ◽  
Nutrient Supplementation ◽  
Face To Face ◽  
Source Of Information

Abstract Objective: To clarify nutrient supplementation usage and primary source of information among pregnant women in China. Design: This cross-sectional study used information on nutrient supplementation and primary source of information collected via face-to-face interviews. Data on the usage of folic acid, calcium/vitamin D, iron, vitamins, docosahexaenoic acid, and other dietary supplements were collected. Primary source of information were categorized as family/relatives, friends/co-workers, the Internet, books/magazines, television/radio, doctors, other people, and oneself. Setting: Maternal and Child Health Hospital in Chengdu, China. Participants: 1081 Chinese pregnant women aged ≥ 20 years with singleton pregnancies. Results: In all three trimesters of pregnancy, usage was highest and most stable for folic acid (81.7%), followed by vitamins (vitamin A, B-group vitamins, vitamin C, and multivitamins; 75.0%), whereas calcium/vitamin D (51.4%) and iron (18.1%) usage was low, potentially indicating a deficiency risk. All supplementation usage percentages increased with pregnancy duration (p < 0.05). Notably, approximately 10% of the pregnant women in our study did not use any nutrient supplementation, and this was especially common in early pregnancy. More than 50% of the women reported getting information on nutrient supplementation from family members, and about 30% reported getting this information from doctors. Conclusions: Among pregnant women in China, awareness about nutrient supplementation increases as the pregnancy progresses, but some types of nutrient supplementation (such as calcium/vitamin D and iron) remain at low levels. It is necessary to pay more attention to the health education of pregnant women in China, and the influence of family members should be emphasized.

scholarly journals Perceived Knowledge of Scheme Members and Their Satisfaction with Their Medical Schemes: A Cross-Sectional Study in South Africa.

2021 ◽  
Author(s):  
Francis M’bouaffou ◽  
Eric Buch ◽  
Evelyn Thsehla ◽  
Steve Olorunju
Keyword(s):  
South Africa ◽  
Service Providers ◽  
Primary Source ◽  
Cross Sectional Study ◽  
Cross Sectional Survey ◽  
Perceived Knowledge ◽  
Cross Sectional ◽  
Perceived Satisfaction ◽  
Private And Public ◽  
The Cost

Abstract Background: South Africa has a dual healthcare system comprised of private and public sectors covering 16% and 84% of the population, respectively. Medical schemes are the primary source of health insurance in the private sector. The aim of this study was to assess the perceived knowledge and satisfaction of open medical schemes members. Methods: A cross-sectional survey was conducted using a stratified systematic sample of members from 22 open medical schemes. Nine hundred and sixty members were requested to complete an online semi-structured questionnaire to determine their perceived knowledge and satisfaction with their schemes. We tested to see if variables such as age, gender, years of membership, education, income or having a chronic disease were associated with better-perceived knowledge or satisfaction. We calculated a composite perceived knowledge and satisfaction score, for which a score above 60th percentile for perceived knowledge and 60th for perceived satisfaction were considered good perceived knowledge and good perceived satisfaction with their schemes.Results: Respondents, generally perceived themselves to have good knowledge and were satisfied with their schemes except for accessibility to doctors under the designated service providers arrangement. Overall, members were satisfied, especially with the quality of service from their designated service providers (DSPs) and their schemes. However, only 9% were satisfied with accessibility to doctors under their DSP arrangement, 25% were satisfied with the cost of scheme membership and only 46% were satisfied with the prescribed minimum benefit package. The test for association showed that years of medical schemes membership, perceived knowledge of the prescribed minimum benefits, better income and laying a complaint were associated with better-perceived knowledge. Conclusion: Medical schemes remain a key element of private healthcare in South Africa. The analysis shows that medical schemes, should put more effort into the accessibility of general practitioner under their designated service providers. Furthermore, the PMBS should be reviewed to provide a comprehensive benefits basket without co-payment for members as recommended by the Medical Schemes Act Amendment Bill of 2018.

scholarly journals The contribution of domestic animals to the transmission of schistosomiasis japonica in the Lindu Subdistrict of the Central Sulawesi Province, Indonesia

2019 ◽  
Vol 12 (10) ◽  
pp. 1591-1598 ◽  
Author(s):  
Novericko Ginger Budiono ◽  
Fadjar Satrija ◽  
Yusuf Ridwan ◽  
Ekowati Handharyani ◽  
Sri Murtini
Keyword(s):  
Infection Intensity ◽  
Primary Source ◽  
Domestic Animal ◽  
Laboratory Method ◽  
Schistosomiasis Japonica ◽  
Cross Sectional Survey ◽  
Chi Square ◽  
Cross Sectional ◽  
The Government ◽  
Central Sulawesi

Background and Aim: Schistosomiasis is endemic in Indonesia and is found in three remote areas in Central Sulawesi Province. Non-human mammals serve as reservoir hosts, meaning the disease is zoonotic. The previous schistosomiasis studies in animals from the Lindu Subdistrict did not determine which domestic animal species can serve as the primary source of transmission. No animals have been treated in Indonesia to control the disease; therefore, the parasite's life cycle is not blocked entirely. This study aimed to determine the prevalence and identify the risk factors associated with, Schistosoma japonicum infection in animals, and identify animals' relative contributions to S. japonicum transmission in the Lindu Subdistrict. Materials and Methods: A cross-sectional survey of S. japonicum infected animals was conducted in five villages of the Lindu Subdistrict. Fecal samples were collected from 134 selected animals (13 cattle, 26 buffaloes, 28 horses, 59 pigs, and 8 dogs). S. japonicum infection and infection intensity were determined using the Danish Bilharziasis Laboratory method. Environmental contamination with schistosome eggs was measured. The data were analyzed using a Chi-square test. Results: The overall prevalence of schistosomiasis was 32.9%, with the prevalence of infection in each species of animal at 61.5% in cattle, 42.3% in buffaloes, 25.0% in horses, 35.6% in pigs, and 12.5% in dogs. Free-range pigs were 8.667 times more likely to have S. japonicum infection than pigs kept in cages. Buffaloes, cattle, and horses were the primary sources of S. japonicum egg contamination, with relative transmission indices of 59.15%, 22.80%, and 10.61%, respectively. Conclusion: Bovines and horses are the main contributors to schistosomiasis transmission in the Lindu Subdistrict. In conjunction with other schistosomiasis control programs, the government should treat infected animals living within endemic areas where there are high infection rates of S. japonicum.

scholarly journals Pharmacists’ Perception of the Coronavirus Pandemic (COVID-19) in Jordan: A Cross-Sectional Study

2021 ◽  
Vol 18 (21) ◽  
pp. 11541
Author(s):  
Tamara Al-Daghastani ◽  
Odate Tadros ◽  
Shereen Arabiyat ◽  
Deema Jaber ◽  
Husam AlSalamat
Keyword(s):  
Online Survey ◽  
Vaccine Development ◽  
Primary Source ◽  
Cross Sectional Study ◽  
Survey Study ◽  
Sources Of Information ◽  
Cross Sectional ◽  
Protection Measures ◽  
Second Wave

Objectives: To analyze the role of pharmacists during the COVID-19 pandemic, to measure pharmacists’ attitude toward COVID-19 safety measures (wearing masks, wearing gloves, isolation shield, good hygiene, etc.), and explore their perspectives regarding a second wave of the virus. Methods: This cross-sectional online survey study was conducted in Jordan during the COVID-19 outbreak in July 2020 to discuss Jordanian pharmacists’ awareness of safety at their workplace during the COVID-19 outbreak, their sources of information, and their predictions for COVID-19 vaccination. Results: The participants (n = 311) were all pharmacists mostly aged between 23–30 years old (45%) and female (83%). The primary source of information about COVID-19 was social networking (38.9%). Pharmacists were committed to social distancing (86.5%) and wearing masks (76.2%). They expressed levels of agreement to their role in decreasing COVID-19 spread (94.2%) and correcting false information (94.5%); they expressed levels of expectation toward concern about a second COVID-19 wave (83%) that would be more severe than the previous one (43.4%). Pharmacists expected that an influenza vaccine might be helpful in decreasing severity and spread of the COVID-19 pandemic (56.9%). Pharmacists expected COVID-19 vaccine development within 6 months of administering our study survey (84.9%) and that vaccination might be effective in preventing COVID-19 (93%) infection. Conclusion: Pharmacists expressed positive roles on COVID-19 spread through exemplary actions, self-commitment to protection measures, and public health awareness. Social media as a source of health information should be cautiously investigated, and pharmacists should always refer to evidence-based sources. The role of pharmacists is particularly important for the upcoming era of COVID-19 vaccination administration and awareness.

Imaging reflection-blind areas using transmitted PS-waves

Geophysics ◽  
2006 ◽  
Vol 71 (6) ◽  
pp. S241-S250 ◽  
Author(s):  
Yi Luo ◽  
Qinglin Liu ◽  
Yuchun E. Wang ◽  
Mohammed N. AlFaraj
Keyword(s):  
Mode Conversion ◽  
Imaging Techniques ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Reflected Waves ◽  
Prestack Migration ◽  
Reflection Data ◽  
Time Migration ◽  
Transmitted Waves ◽  
Vsp Data

We illustrate the use of mode-converted transmitted (e.g., PS- or SP-) waves in vertical seismic profiling (VSP) data for imaging areas above receivers where reflected waves cannot illuminate. Three depth-domain imaging techniques — move-out correction, common-depth-point (CDP) mapping, and prestack migration — are described and used for imag-ing the transmitted waves. Moveout correction converts an offset VSP trace into a zero-offset trace. CDP mapping maps each sample on an input trace to the location where the mode conversion occurs. For complex media, prestack migration (e.g., reverse-time migration) is used. By using both synthetic and field VSP data, we demonstrate that images derived from transmissions complement those from reflections. As an important application, we show that transmitted waves can illuminate zones above highly de-viated or horizontal wells, a region not imaged by reflection data. Because all of these benefits are obtained without extra data acquisition cost, we believe transmission imag-ing techniques will become widely adopted by the oil in-dustry.

Nitrate in Groundwater and Health Risk Assessment: A Cross-Sectional Study in Three Villages in Tanah Merah District, Kelantan, Malaysia During Paddy Pre-Planting Season

2020 ◽  
Author(s):  
Muhammad Syafiq N ◽  
◽  
Shaharuddin MS ◽  
Zaenal Abidin ◽  
◽  
...  
Keyword(s):  
Risk Assessment ◽  
Drinking Water ◽  
Health Risk ◽  
Health Risk Assessment ◽  
Hazard Quotient ◽  
Primary Source ◽  
Cross Sectional Study ◽  
Sectional Study ◽  
Nitrate Level ◽  
Cross Sectional

ABSTRACT Introduction: Contamination of nitrate is one of the most common groundwater problems worldwide. Around 70% of residents in the state of Kelantan still rely on groundwater as their primary source of water supply. Extensive usage of fertilizer in agricultural areas may cause nitrate leaching into the groundwater. This study aimed to determine the level of nitrate in groundwater and health risk assessment at three villages in Tanah Merah District, Kelantan, Malaysia. Subjects and Method: This was a cross-sectional study conducted at Tanah Merah district, Kelantan, in January 2020. A total of 52 residents was selected by purposive sampling. The inclusion criteria for study subjects were long life residents, age ≥18 years old, and groundwater as a primary source of drinking supply. The study variables were (1) Level of nitrate in groundwater measured according to age (year), depth (meter), and distance (meter) of well from the agricultural area; and (2) Health risk assessment measured by hazard quotient (HQ). A set of questionnaires consisted of four sections to gather information related to socio-demographic, water usage, living environment, and health status. Groundwater samples were collected in duplicates and were analysed using a Hanna Instruments portable pH/ORP/ISE meter with an attached nitrate electrode. The data were reported descriptively. Results: Nitrate levels were found to be under the maximum acceptable value of 10 mg/L, as stated by the Drinking Water Quality Standard of Malaysia. Nitrate level ranged from 0.22 to 8.81 mg/L (Mean= 2.94; SD= 2.27). Spearman rho correlation showed that nitrate level was significantly and negatively correlated the age of wells (r= -0.31; p= 0.025). Nitrate level was not significantly correlated with the depth (r= 0.19; p= 0.183) and distance of wells (r= -0.05; p= 0.751). Hazard quotient (HQ) for all study subjects was <1, which means that exposure to nitrate contained drinking water in study subjects was not detrimental to health. Conclusion: Nitrate levels were below the maximum acceptable value, but continuous monitoring from health authorities is essential since other seasons of paddy planting may contribute higher deposition of nitrate into groundwater. Keywords: nitrate, groundwater, levels, hazard quotient, Tanah Merah Correspondence: Muhammad Syafiq N. Department of Environmental and Occupational Health, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia. UPM Serdang, Selangor, Malaysia. Email: [email protected]. Mobile: +601140731881. DOI: https://doi.org/10.26911/the7thicph.01.27

A multioffset, three‐component VSP study in the Sudbury Basin

Geophysics ◽  
1995 ◽  
Vol 60 (2) ◽  
pp. 341-353 ◽  
Author(s):  
Xiao‐Gui Miao ◽  
Wooil M. Moon ◽  
B. Milkereit
Keyword(s):  
Data Processing ◽  
Seismic Reflection ◽  
Velocity Structure ◽  
Least Square ◽  
Seismic Reflection Data ◽  
S Waves ◽  
Velocity Models ◽  
Reflection Data ◽  
Wavefield Separation ◽  
Vsp Data

A multioffset, three‐component vertical seismic profiling (VSP) experiment was carried out in the Sudbury Basin, Ontario, as a part of the LITHOPROBE Sudbury Transect. The main objectives were determination of the shallow velocity structure in the middle of the Sudbury Basin, development of an effective VSP data processing flow, correlation of the VSP survey results with the surface seismic reflection data, and demonstration of the usefulness of the VSP method in a crystalline rock environment. The VSP data processing steps included rotation of the horizontal component data, traveltime inversion for velocity analysis, Radon transform for wavefield separation, and preliminary analysis of shear‐wave data. After wavefield separation, the flattened upgoing wavefields for both P‐waves and S‐waves display consistent reflection events from three depth levels. The VSP-CDP transformed section and corridor stacked section correlate well with the high‐resolution surface reflection data. In addition to obtaining realistic velocity models for both P‐ and S‐waves through least‐square inversion and synthetic seismic modeling for the Chelmsford area, the VSP experiment provided an independent estimation for the reflector dip using three component hodogram analysis, which indicates that the dip of the contact between the Chelmsford and Onwatin formations, at an approximate depth of 380 m in the Chelmsford borehole, is approximately 10.5° southeast. This study demonstrates that multioffset, three‐component VSP experiments can provide important constraints and auxiliary information for shallow crustal seismic studies in crystalline terrain. Thus, the VSP technique bridges the gap between the surface seismic‐reflection technique and well‐log surveys.

VSP CASE HISTORY, KANPA 1A, THE WESTERN OFFICER BASIN

1985 ◽  
Vol 25 (1) ◽  
pp. 254
Author(s):  
T.J.C. Prudence ◽  
J. Flentri
Keyword(s):  
Seismic Profile ◽  
Field Configuration ◽  
Synthetic Seismogram ◽  
Target Interval ◽  
Seismic Section ◽  
Temporal Sampling ◽  
Consistent Field ◽  
Vsp Data ◽  
Tube Wave ◽  
Zero Phase

The Kanpa 1A Vertical Seismic Profile (VSP) was conducted for Shell by Schlumberger and incorporated variable time and depth sampling, different source offsets and recording in cased and uncased hole. Processing was performed using Shell proprietary programs, with particular attention to:Editing and resampling of the data setSeparation of upgoing and downgoing waves using FK and median filtersComparison of gain recovery based on modelling the amplitude decay of direct arrivals with an averaging process (AGC)Sensitivity of the final VSP stack to blanking of residual tube wave noiseZero-phase whitening of the VSP traceStacked VSP traces for Kanpa 1A were compared with a zero-phase seismic section and synthetic seismogram at the well. The VSP/seismic match is good and, due to poor synthetic/seismic correlation, was the basis for the final seismic/well tie. Interpretation of deep VSP data enabled the estimation of formation boundaries below the total depth of the well.It is concluded that VSPs can be invaluable in establishing well ties where seismic is poor or when detailed correlation is required (e.g. stratigraphic traps). Reflectors "ahead of the bit" can be interpreted from VSPs based on assumed velocities and VSP/seismic tie, and the predicted thickness and seismic character of the target interval. A consistent field configuration is recommended for acquisition with attention to tube wave suppression and adequate spatial and temporal sampling. Previous processing experience is advantageous if quick and reliable VSP results are required for decisions while drilling.

scholarly journals Exploring discrimination towards pharmacists in practice settings

2020 ◽  
Vol 18 (3) ◽  
pp. 1966
Author(s):  
Lik D. Chun ◽  
Rebecca Ye ◽  
Kyle J. Wilby
Keyword(s):  
Sexual Harassment ◽  
Pharmacy Practice ◽  
Primary Source ◽  
Verbal Abuse ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
Phase Discrimination ◽  
Study Support ◽  
The University ◽  
The Impact

Background:  Discrimination towards pharmacists, as a public-facing health professional group, is reported but not well-studied. Objectives:  The aims of this study were to identify accounts of discrimination in pharmacy practice and to explore the nature and impacts of and discrimination experienced by pharmacists. Methods:  A cross-sectional survey was emailed to practice-based preceptors associated with the School of Pharmacy at the University of Otago. The survey included demographic questions, in addition to questions asking about the frequency and sources of different types of discrimination and abuse encountered in practice. Survey respondents could also provide their contact information for follow-up interviews. Interviews occurred after completion of the survey to better understand the nature of discrimination in pharmacy practice. A thematic analysis of interview transcripts was conducted to identify pertinent themes. Results: A total of 43 participants completed the survey. A total of 29 (67.4%) respondents reported experiencing discrimination in pharmacy practice. The most common types of discrimination experienced included discrimination based on gender, appearance, or past, present, or expected pregnancy. Verbal abuse and sexual harassment were also frequently reported. Most discrimination was sourced from patients, colleagues, or supervisors/leaders. Discrimination specific to pregnancy was largely sourced from supervisors/leaders. Verbal abuse was sources primarily from patients, patient’s family, supervisors/leaders, and other healthcare professionals. Patients were the primary source of sexual harassment. Three themes were identified from the interview phase: Discrimination occurs for a variety of reasons from different sources with different behaviors, the impact on a person is individualized/personal, and preventative strategies can be broad and encompass multiple layers of society. Conclusions:  Findings of this study support the notion that training programs must adjust to adequately train pharmacists with effective coping strategies, prevention mechanisms, and resilience building strategies. Pharmacist employers should also be accountable to creating zero tolerance workplaces and providing route maps for how pharmacists report and navigate situations when faced with discrimination. Doing so may result in a better equipped workforce that is able to navigate the pressures encountered through discrimination in practice.

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