Aeolian sediments in paleowetland deposits of the Las Vegas Formation

2021 ◽  
pp. 1-13
Author(s):  
Harland L. Goldstein ◽  
Kathleen B. Springer ◽  
Jeffrey S. Pigati ◽  
Marith C. Reheis ◽  
Gary L. Skipp
Keyword(s):  
Particle Size ◽  
Las Vegas ◽  
Groundwater Discharge ◽  
Geochemical Data ◽  
Median Particle Size ◽  
Las Vegas Valley ◽  
Southern Nevada ◽  
Aeolian Sediments ◽  
Median Particle ◽  
Alluvial Material

Abstract The Las Vegas Formation (LVF) is a well-characterized sequence of groundwater discharge (GWD) deposits exposed in and around the Las Vegas Valley in southern Nevada. Nearly monolithologic bedrock surrounds the valley, which provides an excellent opportunity to test the hypothesis that GWD deposits include an aeolian component. Mineralogical data indicate that the LVF sediments are dominated by carbonate minerals, similar to the local bedrock, but silicate minerals are also present. The median particle size is ~35 μm, consistent with modern dust in the region, and magnetic properties contrast strongly with local bedrock, implying an extralocal origin. By combining geochemical data from the LVF sediments and modern dust, we found that an average of ~25% of the LVF deposits were introduced by aeolian processes. The remainder consists primarily of authigenic groundwater carbonate as well as minor amounts of alluvial material and soil carbonate. Our data also show that the aeolian sediments accumulated in spring ecosystems in the Las Vegas Valley in a manner that was independent of both time and the specific hydrologic environment. These results have broad implications for investigations of GWD deposits located elsewhere in the southwestern U.S. and worldwide.

Late Wisconsin Groundwater Discharge Environments of the Southwestern Indian Springs Valley, Southern Nevada

1989 ◽  
Vol 31 (3) ◽  
pp. 351-370 ◽  
Author(s):  
Jay Quade ◽  
William L. Pratt
Keyword(s):  
Las Vegas ◽  
Groundwater Discharge ◽  
Wet Meadow ◽  
Fine Grained ◽  
Las Vegas Valley ◽  
Southern Nevada ◽  
Stratigraphic Position ◽  
Depositional Systems ◽  
Key Features ◽  
Marsh Sediments

AbstractBadland exposures in the Indian Springs Valley, southern Nevada, contain evidence of formerly widespread spring and seep discharge. The stratigraphic position and appearance of most of these deposits suggests correlation with late Wisconsin (30,000 to ca. 10,000 yr B.P.) marsh sediments in nearby Las Vegas Valley. Previously, all these deposits have been loosely described as lacustrine because of the presence of extensive green mudstones associated with aquatic mollusks. However, this association also typifies modern groundwater discharge environments in many basins of northeast Nevada such as the Steptoe Valley, basins often without hydrographic closure. Such analogs best explain the origin of late Wisconsin fine-grained deposits in the unclosed southwestern arm of the Indian Springs Valley. Key features of these depositional systems are the lack of shoreline deposits, the presence of a broad belt of subaerially deposited plae-brown silts surrounding spring, “wet meadow,” and marsh deposits, and the intermixture of terrestrial and aquatic mollusks in most horizons where mollusks occur.

Vertical axis rotations in the Las Vegas Valley Shear Zone, southern Nevada: Paleomagnetic constraints on kinematics and dynamics of block rotations

Tectonics ◽  
1994 ◽  
Vol 13 (4) ◽  
pp. 769-788 ◽  
Author(s):  
Leslie J. Sonder ◽  
Craig H. Jones ◽  
Stephen L. Salyards ◽  
Kathleen M. Murphy
Keyword(s):  
Shear Zone ◽  
Las Vegas ◽  
Vertical Axis ◽  
Kinematics And Dynamics ◽  
Las Vegas Valley ◽  
Southern Nevada

Ongoing restoration and management of Las Vegas Wash: an evaluation of success criteria

Water Policy ◽  
2014 ◽  
Vol 16 (4) ◽  
pp. 720-738 ◽  
Author(s):  
Mahesh Gautam ◽  
Kumud Acharya ◽  
Seth A. Shanahan
Keyword(s):  
Las Vegas ◽  
Management Strategies ◽  
Management Program ◽  
Lessons Learned ◽  
Lake Mead ◽  
Channel System ◽  
Las Vegas Valley ◽  
Success Criteria ◽  
Southern Nevada ◽  
Channel Degradation

The Las Vegas Wash is a dynamic channel system that drains the Las Vegas Valley (3,950 km2) into Lake Mead and the lower Colorado River, which provides drinking water to southern California, Arizona, and southern Nevada. In the last few decades the Las Vegas Wash has undergone massive changes in terms of channel degradation and bank erosion followed by recovery and restoration efforts. The evolution of the Las Vegas Wash is interlinked with urbanization, water use, and wastewater discharge. This article reviews the historical dynamics of the Las Vegas Wash in the context of restoration: evaluates the ongoing activities in the Las Vegas Wash against an established framework and success criteria; summarizes lessons learned; and discusses challenges. The ongoing activities in the Las Vegas Wash differ from other regional restoration projects in that there is a lack of an appropriate historical reference to which restoration goals should be targeted. Keys to the success of the Las Vegas Wash restoration and management program appear to be strong interagency collaboration, funding availability, effective outreach and monitoring efforts, and adaptive management strategies based on pragmatic urban values. There is a potential for realignment of existing resources for more practical ecological restoration goals.

Influence of Powder Particle Size of Slurries on Mechanical Properties of Porous Hydroxyapatite Ceramics

2005 ◽  
Vol 284-286 ◽  
pp. 365-368 ◽  
Author(s):  
Yin Zhang ◽  
Yoshiyuki Yokogawa ◽  
Tetsuya Kameyama
Keyword(s):  
Particle Size ◽  
Flexural Strength ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Particle Sizes ◽  
Wet Milling ◽  
Median Particle Size ◽  
Powder Characteristics ◽  
Median Particle

The effect of different particle sizes on the flexural strength and microstructure of three different types of hydroxyapatite (HAp) powders was studied. The powder characteristics of laboratory synthesized HAp powder (Lab1 and Lab2) were obtained through a wet milling method, and the median particle size and the specific surface area of powders are different with the dryness period. The median particle sizes of Lab1 and Lab2 are 0.34 µm and 0.74 µm, and the specific surface areas of Lab1 and Lab2 are 38.01 m2/g and 19.77 m2/g. The commercial HAp had median particle size of 1.13 µm and specific surface area of 11.62m2/g. The different powder characteristics affected the slip characteristics, and the flexural strength and microstructure of the sintered porous HAp bodies are also different. The optimum value for the minimum viscosity in these present HAp slip with respect to its solid loading and the optimum amount of the deflocculant were investigated. The flexural strengths of the porous HAp ceramics prepared by heating at 1200°C for 3 hrs in air were 17.59 MPa for Lab1 with a porosity of 60.48％, 10.51 MPa for Lab2 with a porosity of 57.75％, and 3.92 MPa for commercial HAp with a porosity of 79.37％.

Obtaining and research of pharmaceutical properties of antiemetics in a form of powder for inhalation

2021 ◽  
Author(s):  
Igor M. Ivanov ◽  
Tatiana B. Pechurina ◽  
Nikolai G. Vengerovich ◽  
Mikhail A. Yudin ◽  
Aleksandr S. Nikiforov ◽  
...  
Keyword(s):  
Particle Size ◽  
Dosage Form ◽  
Production Method ◽  
Particle Fraction ◽  
Median Particle Size ◽  
Antiemetic Drugs ◽  
Median Particle ◽  
Pharmaceutical Properties ◽  
Mass Median ◽  
Respirable Particle

Samples of antiemetic drugs (ondansetronum, palonosetronum, metoclopramidum) in the form of powder for inhalation have been developed by the method of spray drying. The granulometric composition, hygroscopicity and aerodynamic distribution of aerosol particles of the drugs have been investigated. The dosage form of the powder for inhalation of antiemetics (ondansetronum and palonosetronum) in terms of its particle size distribution, hygroscopicity and content of the agent corresponds to those for inhalation using dry powder inhalers. In the study of the phase-dispersed composition of aerosol, ondansetronum and palonosetronum in the dosage form of powder for inhalation as part of the HandiHaler inhaler (at a flow rate of 60 l / min) showed high rates of the released dose up to 72-76%, respirable particle fraction (up to 5 m) up to 54 -56% and a mass median particle size of about 3 microns. Obtaining the inhaled form of metoclopramide requires optimization of the production method for receiving the product with acceptable pharmaceutical properties.

scholarly journals Extraction of single serve coffee capsules: linking properties of ground coffee to extraction dynamics and cup quality

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
André Eiermann ◽  
Samo Smrke ◽  
Loïc-Marco Guélat ◽  
Marco Wellinger ◽  
Anja Rahn ◽  
...  
Keyword(s):  
Particle Size ◽  
Product Development ◽  
Total Dissolved Solids ◽  
Fine Tuning ◽  
Median Particle Size ◽  
Flow Restriction ◽  
General Rules ◽  
Median Particle ◽  
Ground Coffee ◽  
Cup Quality

Abstract The objective of this paper is to elucidate the variables that govern coffee extraction from single serve coffee capsules. The study was conducted on 43 Nespresso and Nespresso-compatible capsules of the same geometry, from all of which the coffee was extracted on the same machine. This allowed the link between a range of coffee and capsule (input) parameters with coffee brew (output) variables to be studied. It was demonstrated that the most efficient way to increase total dissolved solids in the brew is to use more coffee for extraction, and/or to grind the coffee more finely. However, grinding too finely can lead to excessive flow restriction. The most significant new insight from this study is the importance of the proportion of fines (particles smaller than 100 µm) regarding the capsule extraction dynamics. Capsules with a higher share of fines, for similar median particle size of the ground coffee, led to longer extraction times. General rules applicable for capsule coffee product development were established, although fine-tuning of parameters for successful capsule coffee extraction remains specific to production line and type of coffee.

scholarly journals Preparation of Curcumin Nanosuspension with Gum Arabic as a Natural Stabilizer: Process Optimization and Product Characterization

Processes ◽  
2020 ◽  
Vol 8 (8) ◽  
pp. 970 ◽  
Author(s):  
Bao Hoang Duong ◽  
Hoai Nam Truong ◽  
Quynh Anh Phan Nguyen ◽  
Thuong Nhan Nguyen Phu ◽  
Le Thi Hong Nhan
Keyword(s):  
Particle Size ◽  
High Speed ◽  
Gum Arabic ◽  
Spherical Shape ◽  
Aqueous Solubility ◽  
Polymeric Surfactant ◽  
Median Particle Size ◽  
Curcumin Nanoparticles ◽  
Homogenization Time ◽  
Median Particle

Low aqueous solubility and poor bioavailability of curcumin have limited its application in various fields. One approach to address this issue is to formulate a nanosuspension that incorporates curcumin, which has been previously shown to exhibit remarkably improved solubility in comparison with that of a bare compound. In this study, the preparation process of curcumin nanosuspension was optimized with a median particle size as the outcome. Gum arabic was used as a natural polymeric surfactant and the suspension was formulated using high speed homogenization. Optimization results, realized via a response surface methodology, showed that a minimum median particle size (8.524 µm) could be attained under the following conditions: curcumin:gum arabic ratio of 1:6 g/g; homogenization speed of 8300 rpm and homogenization time of 40 min. Under these conditions, the particle size of obtained suspension was shown to be consistent for around seven days without major aggregation. The homogenization process could be scaled up to five times in terms of suspension volume. TEM also showed that curcumin nanoparticles had a nearly spherical shape and homogeneous structure with a size range of 40–80 nm.

scholarly journals Implementing Feedback Granule Size Control in a Continuous Dry Granulation Line Using Controlled Impeller Speed of the Granulation Unit, Compaction Force and Gap Width

2020 ◽  
Author(s):  
Annika Wilms ◽  
Andreas Teske ◽  
Robin Meier ◽  
Raphael Wiedey ◽  
Peter Kleinebudde
Keyword(s):  
Particle Size ◽  
Process Parameters ◽  
Control Strategies ◽  
Granule Size ◽  
Oral Dosage ◽  
Impeller Speed ◽  
Median Particle Size ◽  
Dry Granulation ◽  
Median Particle ◽  
Roll Compaction

Abstract Purpose In continuous manufacturing of pharmaceuticals, dry granulation is of interest because of its large throughput capacity and energy efficiency. In order to manufacture solid oral dosage forms continuously, valid control strategies for critical quality attributes should be established. To this date, there are no published control strategies for granule size distribution in continuous dry granulation. Methods In-line laser diffraction was used to determine the size of granules in a continuous roll compaction/dry granulation line (QbCon® dry). Different process parameters were evaluated regarding their influences on granule size. The identified critical process parameters were then incorporated into control strategies. The uncontrolled and the controlled processes were compared based on the resulting granule size. In both processes, a process parameter was changed to induce a shift in median particle size and the controller had to counteract this shift. Results In principle, all process parameters that affect the median particle size could also be used to control the particle size in a dry granulation process. The sieve impeller speed was found to be well suited to control the median particle size as it reacts fast and can be controlled independently of the throughput or material. Conclusion The median particle size in continuous roll compaction can be controlled by adjusting process parameters depending on real-time granule size measurements. The method has to be validated and explored further to identify critical requirements to the material and environmental conditions.

New 40Ar/39Ar isotopic dates from Miocene volcanic rocks in the Lake Mead area and southern Las Vegas Range, Nevada

1998 ◽  
Vol 35 (5) ◽  
pp. 495-503 ◽  
Author(s):  
Stephen S Harlan ◽  
Ernest M Duebendorfer ◽  
Jack E Deibert
Keyword(s):  
Las Vegas ◽  
Volcanic Rocks ◽  
Normal Fault ◽  
Vertical Axis ◽  
Lake Mead ◽  
Basin And Range Province ◽  
Red Sandstone ◽  
Las Vegas Valley ◽  
Western Lake ◽  
Southern Nevada

New 40Ar/39Ar dates on volcanic rocks interlayered with synextensional Miocene sedimentary rocks in the western Lake Mead area and southern end of the Las Vegas Range provide tight constraints on magmatism, basin formation, and extensional deformation in the Basin and Range province of southern Nevada. Vertical axis rotations associated with movement along the Las Vegas Valley shear zone occurred after 15.67 ± 0.10 Ma (2 sigma ), based on a 40Ar/39Ar date from a tuff in the Gass Peak formation in the southern Las Vegas Range. Basaltic magmatism in the western Lake Mead area began as early as 13.28 ± 0.09 Ma, based on a date from a basalt flow in the Lovell Wash Member of the Horse Spring Formation. Isotopic dating of a basalt from the volcanic rocks of Callville Mesa indicates that these rocks are as old as 11.41 ± 0.14 Ma, suggesting that volcanic activity began shortly after formation of the Boulder basin, the extensional basin in which the informally named red sandstone unit was deposited. The red sandstone unit is at least as old as 11.70 ± 0.08 Ma and contains megabreccia deposits younger than 12.93 ± 0.10 Ma. This result shows that formation of the Boulder basin was associated with development of topographic relief that was probably generated by movement along the Saddle Island low-angle normal fault. Stratal tilting associated with extension occurred both prior to and after 11.5 Ma.

Electroacoustic determination of size and zeta potential of casein micelles in skim milk

1996 ◽  
Vol 63 (3) ◽  
pp. 387-404 ◽  
Author(s):  
Theresa Wade ◽  
James K. Beattie ◽  
William N. Rowlands ◽  
Mary-Ann Augustin
Keyword(s):  
Particle Size ◽  
Zeta Potential ◽  
Skim Milk ◽  
Median Particle Size ◽  
Casein Micelles ◽  
Median Particle ◽  
Decreasing Ph ◽  
Good Agreement

SummaryMeasurements of the zeta potential and particle size of casein micelles in skim milk suspensions at natural and lower pH have been made using the technique of electroacoustics. This technique requires no dilution or change of environment of the casein micelles. The zeta potential obtained at natural pH for a commercial skim milk suspension was −18 mV; it became less negative with decreasing pH. The median particle size observed at natural pH for a commercial skim milk suspension was 0·2 εm, in good agreement with previously reported values. The particle size increased as the pH was decreased.

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