Enhanced reverse saturable absorption and optical limiting in heavy-atom-substituted phthalocyanines

The reverse saturable absorption and the optical-limiting response of metal phthalocyanines can be enhanced by use of the heavy-atom effect. Phthalocyanines containing heavy-metal atoms, such as In, Sn, and Pb, show a nearly factor-of-2 enhancement in the ratio of effective excited-state to ground-state absorption cross sections compared with those containing lighter atoms, such as Al and Si. In an f/8 optical geometry, homogeneous solutions of heavy-metal phthalocyanines, at 30% linear transmission, limit 8-ns 532-nm laser pulses to ≤ 3 µJ the energy for 50% probability of eye damage) for incident energies as high as 800 µJ

Relationship Between Parental Occupational Class and Success in Science Fair Competition

Higher Educatio

Initiating a Selling Library and Personal Paperback Library Program in the Biological Sciences

The publication of quality content paperback books in the biological sciences presents a vast source of information to supplement the regular high school class. The low-cost, conveniently-managed, and well-written books could serve to greatly increase the interest and knowledge of the student if a method could be devised to introduct these books to the student and provide him with the opportunity to purchase personal copies. Several colleges have departments that recommend paperback texts, allowing the student to buy many books for the price of one, thereby enriching the course. A survey of libraries that stock both paperback and hard bound books of the same title indicates a strong preference of students for paperback books, as evidenced by check-out records. A program to initiate a selling library for paperback books and a personal paperback library in the biological sciences seemed to be the most effective method of introducing and stimulating the interest of the students in these books. Letters of inquiry were sent to publishers of paperback books, and a pilot plan was devised for one school system. The paperback selling library and personal paperback library program in the biological sciences can be organized and administered in the high school with very few difficulties and seems to show great promise. Most publishers are willing to give regular bookstore discounts, and many supply display racks free or at low prices. It is possible for a science club with faculty advisor to operate the bookstore, complete with displays, advertising, accepting of orders and delivery of books within the school building. The profit from sales may be used to order more books, and publishers will accept return of books not sold for full refund. This report outlines one method of organizing and administering the program.Natural Scienc

Estimating the Potential for Conservation and Farming in the Amazon and Cerrado under Four Policy Scenarios

Since 2013, clearing rates have rapidly increased in the Amazon and Cerrado biomes. This acceleration has raised questions about the efficacy of current regional public and private conservation policies that seek to promote agricultural production while conserving remnants of natural vegetation. In this study, we assessed conservation and agricultural outcomes of four potential policy scenarios that represent perfect adherence to private sector, zero-deforestation commitments (i.e., the Amazon soy moratorium—ASM and the Amazon cattle agreements—CA) and to varying levels of implementation of the Brazilian Forest Code (FC). Under a zero-clearing scenario, we find that the extent of croplands as of 2017 within the two biomes (31 MHa) could double without further clearing if agriculture were to expand on all previously cleared land that is suitable for crops. Moreover, at least 47 MHa of land that is already cleared but unsuitable for crops would remain available for pasture. Under scenarios in which only legal clearing under the FC could occur, 51 MHa of additional natural vegetation could be cleared. This includes as many as 1 MHa of nonforest vegetation that could be cleared in the Amazon biome without triggering the ASM and CA monitoring systems. Two-thirds of the total vegetation vulnerable to legal clearing is located within the Cerrado biome, and 19 MHa of this land is suitable for cropland expansion. Legal clearing of all of these areas could reduce biodiversity persistence by 4% within the two biomes, when compared with the zero-clearing scenario, and release up to 9 PgCO2e, with the majority (75%) coming from the Cerrado biome. However, when we considered the potential outcomes of full implementation of the FC, we found that 22% (11 MHa) of the 51 MHa of vegetation subject to legal clearing could be protected through the environmental quotas market, while an additional 1 MHa should be replanted across the two biomes, predominantly in the Amazon biome (73% of the area subject to replanting). Together, quotas and replanting could prevent the release of 2 PgCO2e that would otherwise be emitted if all legal clearing occurred. Based on our results, we conclude that ongoing legal clearing could create additional space for cropland and cattle production beyond the substantial existing stocks of cleared areas but would significantly impair local carbon and biodiversity stocks.</jats:p

Understanding Deleted File Decay on Removable Media using Differential Analysis

Digital content created by picture recording devices is often stored internally on the source device, on either embedded or removable media. Such storage media is typically limited in capacity and meant primarily for interim storage of the most recent image files, and these devices are frequently configured to delete older files as necessary to make room for new files. When investigations involve such devices and media, it is sometimes these older deleted files that would be of interest. It is an established fact that deleted file content may persist in part or in its entirety after deletion, and identifying the nature of file fragments on digital media has been an active research area for years. However, very little research has been conducted to understand how and why deleted file content persists (or decays) on different media and under different circumstances. The research reported here builds upon prior work establishing a methodology for the study of deleted file decay generally, and the application of that methodology to the decay of deleted files on traditional computing systems with spinning magnetic disks. In this current work, we study the decay of deleted image files on a digital camera with removable SD card storage, and we conduct preliminary experiments for direct SD card and USB storage. Our results indicate that deleted file decay is affected by the size of both the deleted and overwriting files, overwrite frequency, sector size, and cluster size. These results have implications for digital forensic investigators seeking to recover and interpret file fragments

Flight Measurements of the Effect of a Controllable Thrust Reverser on the Flight Characteristics of a Single-Engine Jet Airplane

A flight investigation was undertaken to determine the effect of a fully controllable thrust reverser on the flight characteristics of a single-engine jet airplane. Tests were made using a cylindrical target-type reverser actuated by a hydraulic cylinder through a "beep-type" cockpit control mounted at the base of the throttle. The thrust reverser was evaluated as an in-flight decelerating device, as a flight path control and airspeed control in landing approach, and as a braking device during the ground roll. Full deflection of the reverser for one reverser configuration resulted in a reverse thrust ratio of as much as 85 percent, which at maximum engine power corresponded to a reversed thrust of 5100 pounds. Use of the reverser in landing approach made possible a wide selection of approach angles, a large reduction in approach speed at steep approach angles, improved control of flight path angle, and more accuracy in hitting a given touchdown point. The use of the reverser as a speed brake at lower airspeeds was compromised by a longitudinal trim change. At the lower airspeeds and higher engine powers there was insufficient elevator power to overcome the nose-down trim change at full reverser deflection

Value-Compressed Sparse Column (VCSC): Sparse Matrix Storage for Redundant Data

Compressed Sparse Column (CSC) and Coordinate (COO) are popular compression formats for sparse matrices. However, both CSC and COO are general purpose and cannot take advantage of any of the properties of the data other than sparsity, such as data redundancy. Highly redundant sparse data is common in many machine learning applications, such as genomics, and is often too large for in-core computation using conventional sparse storage formats. In this paper, we present two extensions to CSC: (1) Value-Compressed Sparse Column (VCSC) and (2) Index- and Value-Compressed Sparse Column (IVCSC). VCSC takes advantage of high redundancy within a column to further compress data up to 3-fold over COO and 2.25-fold over CSC, without significant negative impact to performance characteristics. IVCSC extends VCSC by compressing index arrays through delta encoding and byte-packing, achieving a 10-fold decrease in memory usage over COO and 7.5-fold decrease over CSC. Our benchmarks on simulated and real data show that VCSC and IVCSC can be read in compressed form with little added computational cost. These two novel compression formats offer a broadly useful solution to encoding and reading redundant sparse data