Although we illustrated our model on individuals using an amphetamine-like psycho stimulant drug, the methods and rationale are readily extended to the study of marijuana. A key aspect of our model is that we focus on individual performance which allows the researcher to make a clinical assessment at the level of the individual. The model is applicable for researchers interested in using the CVLT or the memory test developed by the senior authors.We would like to note that our model can be used to test the claims of any plant based product.Claims have long been made about memory enhancing benefits of various plant-based products. While some claims have failed in scientific studies, curcumin has been shown in animal models to reduce depression by working on the cognitive impairments it causes, including effects on memory and learning .Flavinol in cocoa has been shown to improve memory in invertebrates , as well as spatial memory in rats .

Natural and synthetic memory supplements have a sizeable market, and sales were estimated to be $643 million in 2015, with the number of supplements available to consumers growing from 4000 to over 80,000 from 2004 to 2016 . Catechin-rich oil palm leaf extract supplements, for example, have been tested on young adults and resulted in increased short-term memory, processing speed, and spatial visual learning after one month .Approximately 15% of people over the age of 65 suffer from Alzheimer’s disease.The implications of studies where memory is improved by natural supplements denote an importance to sort through products with legitimate support for memory enhancement and potential for memory-loss prevention.The mathematical model posed by the authors can be used to do further research on the learning and memory enhancing properties of these plant derivatives in animals, as well as in humans.An area with an immediate need for research due to concern regarding the negative effects of plant-based products on memory is in the growing field of medical marijuana. In the United States, approximately30 states allow marijuana for medical purposes,although individual state regulations vary significantly.An increase in the number of medical marijuana users dictates a need to determine the possible side effects of using this substance.

Of particular concern are the possible effects of marijuana on neurocognitive functioning, including learning and memory .The senior authors’ model can easily be incorporated into various experimental designs and supplement traditional statistical tests. In the example shown here, we used a group design where drug free males and females were compared with males and females who regularly consumed an amphetamine-like psychostimulant drug. The model can also be used in “ABA” designs where participants are exposed to marijuana or other plant based products, subsequently exposed, and then no longer exposed.We recommend people who regularly use marijuana for medical purposes or other plant based products regularly test their memory for identification of early signs of impairment. For those researchers and clinicians who might be interested in modeling the learning curve, when monitoring memory in marijuana users, the senior authors developed an MS Windows application “LCMT” to help model the learning curve from raw learning data in the California Verbal Learning Test and other similar memory tests. This app is available on request from the senior authors.For those who want to constantly monitor the state of their memory on their own, the senior authors developed a Windows application for testing memory called “Memory Monitoring Tool”. This app allows long-lasting memory monitoring and might be used by marijuana users.

One drawback of using natural fibre composites in outdoor applications is their poor weathering properties.Natural fibre composites are finding increasing applications where they are exposed to weathering agents, which can cause changes in the micro structure and the chemical composition of these composites. These changes in turn can modify properties such as strength, modulus, impact resistance and fatigue behavior, which can have adverse effects on the service life of these composites. Therefore for long service life, the weathering phenomenon and how its effects can be mitigated must be understood. The two main sources of natural weathering are UV radiation and moisture. Natural fibers are not only good absorbers of moisture but they are also susceptible to UV radiation. Photochemical degradation by UV light occurs primarily in lignin which is also responsible for colour change .