Three phenomena can be observed from the baseline case AB results at different inlet mass flow rates: the flow above tray 4 always has a lower temperature than that above tray 3 since it is closest to the inlet region; at low inlet mass flow rate , the flow above tray 3 has the highest temperature due to buoyancy effect; and at high inlet mass flow rate , the flow above tray 1 has the highest temperature because it is located closest to the exit. The temperature distribution for case AD is very similar to that of the baseline case due to similar inlet/exit location orientations so that buoyancy is the dominant effect at low inlet mass flow rate . On the other hand, cases BC, BA, and DA have different temperature distributions than the baseline because the inlet and exit are located near the bottom and the top, respectively. Therefore, the temperature of tray 1 is much closer to the inlet temperature and the temperature increases with height except at high mass flow rate where the temperature above tray 4 can be lower than that above tray 3. This is due to strong helical flow mixing inside the room at high inlet mass flow rate, which also explains that the temperature uniformity increases with increasing inlet mass flow rate. Previous studies show that the optimal germination temperature is between 294 K and 297 K. As can be observed from Fig. 11, cases BC, BA, and DA at 0.3, 0.4, and 0.5 kg s−1, respectively, exhibit the desirable temperature range and distribution for lettuce growth. Nevertheless, compared to the baseline at each mass flow rate, case BC at an inlet mass flow rate of 0.3 kg s−1 exhibits the most significant average temperature reduction . Furthermore, indoor grow trays the average temperature of case BC at 0.3 kg s−1 is lower than that of the baseline case at 0.5 kg s−1, which demonstrates the design effectiveness of case BC.
Relative humidity represents the water vapor partial pressure in the IVFS, which has a strong effect on crop growth. It is reported that the ideal RH for lettuce and leafy greens should be between 50–70% . High RH can cause pathogen issues, like mildew and botrytis, and low RH can induce an outer leaf edge burn due to dryness. Therefore, the inlet RH is set to be 85% in this IVFS design. The comparison of RH for each tray between the highest OU and the baseline cases at different inlet mass flow rates is shown in Fig. 12. It can be observed from the baseline case that RH increases with increasing inlet mass flow rate due to the increase of water supply and decreasing room temperature. RH can be calculated from the ratio of the partial pressure of water vapor to the saturation vapor pressure at a given temperature. Therefore, RH can be increased by either increasing water partial pressure or decreasing temperature. In our study, temperature is the dominant parameter because the gas species composition in the system does not vary significantly. Therefore, the trend of RH distribution agrees with that of the temperature distribution in Fig. 11. The only exception exists for the baseline case AB when the inlet mass flow rate is the smallest . Under such conditions, tray 3 has higher temperature and RH than tray 4. To explain this behavior, the results from the CO2 distribution analysis need to be considered. At the lowest inlet flow rate, the flow has lowest circulation and tray 3 is near the end of the fresh inlet flow stream. Therefore, tray 3 has the lowest CO2 and highest H2O concentrations due to photosynthesis as shown in Figs. 10 and 12. Overall, the average RH distributions for cases BC and BA fall within the optimal range.Marijuana use has become increasingly normalized in the US and abroad. Since 1996, California has allowed marijuana for medical use.
An additional 17 states and the District of Columbia have followed suit by either allowing medical marijuana use or legalizing recreation use of marijuana. A trend among young people is smoking marijuana cigars . Marijuana cigars or blunts refer to cannabis rolled with a shell from an inexpensive cigar called a blunt, although any commonly available inexpensive small cigars or cigarillos are likely to be used . Blunt wrappers, which are tobacco leaf rolling papers that come in sealed packages, are also sold for rolling blunts. Due to the tobacco content in the wrapper leaf, smoking marijuana cigars may be considered as concurrent use of marijuana and tobacco. In this paper, we use the term “blunts” to talk about marijuana cigars and the term “blunt cigars” to talk about the inexpensive tobacco cigar that is typically used to make the marijuana cigars. Blunt cigars are cheap, frequently available at urban convenience stores, typically pre-cut with a blunt tip , and sold singly or in small packs of five. The present study examines factors associated with availability of tobacco products commonly used for blunts. Epidemiological surveys indicate that blunts are most commonly used by emerging adults , and that their use is generally increasing across all age groups. In 2005, 3.5% of all American youth aged 12–17 years were estimated to have used blunts in the past month , and a study among young adults aged 18-25 reported that between 2005 and 2008 past month blunts use ranged between 9% and 10.1% . By comparison, in 2011, 4.1% of youth aged 12–17 years, 11% of young adults aged 18-25years, 4.2% of adults aged 26-34 years and 1% of adults aged 35 or older reported using blunts in the past month , 2013. A recent study reported a moderate increase in the annual prevalence of blunt smoking among respondents aged 12-34 years old from 12% in 2004 to 14% in 2010 .
Other studies indicate that blunt smoking appears to be practiced among a growing number of racial/ethnic groups , such as Southeast Asian youth and young adults in California . Previous studies have found that, compared to other intake forms of marijuana, smoking blunts is more associated with male gender, low GPA, poor school attachment, not attending college, not working, and living in low income areas . Also, blunts smokers may have greater odds of being dependent on cannabis and tobacco and are at risk for smoking-related diseases . While tobacco remains the leading cause of preventable and premature death, killing an estimated 443,000 Americans each year , risks associated with marijuana use include impaired respiratory, cardiovascular and cognitive functioning and reduced mental health, as well as impaired driving ability and impaired function in school and at work . Blunts availability is likely to increase blunts use and problems associated with marijuana and tobacco use in local neighborhoods. Previous research suggests that exposure to and availability of drugs increase drug use and abuse . However, very little is known about availability of tobacco products associated with use of blunts. Studying the associations between neighborhood characteristics and availability of tobacco products used for blunts may help to identify areas at risk for blunts use and help policymakers and community advocates make better decisions about allocation of prevention resources. Analyzing 2000-2003 data from the National Survey on Drug Use and Health , Golub and colleagues showed that more than half of past-30-day marijuana users also reported current use of blunts. Among current blunts users, over two-thirds reported no current use of cigars, vertical grow racks for sale indicating blunts smokers may not define this practice as tobacco use. Similarly, a recent study suggested that young people recognize blunts as a form of marijuana use but do not recognize it as cigar use . Qualitative studies have also shown that youths may not consider blunts smoking to be a form of cigar use at all . These studies suggest the importance of studying the relationships between availability of tobacco products associated blunts use and societal-level influences related to normalization of marijuana use. Increased recognition of “recreational drug use” and increased support for legalizing some forms of marijuana use may contribute to normalization of marijuana and therefore to availability of products associated with blunts use. Societal-level influences related to normalization of marijuana use in the community may include rates of adult marijuana use. Recent studies have found that prevalence of adult drinking or smoking in the community are associated with increased underage drinking and youth cigarette smoking . These studies suggested that the level of adult drug use in the community reflect both community drug norms and availability. Medical marijuana policy and availability should also be considered as social influences related to normalization of marijuana. Our previous studies indicated that tobacco and alcohol policies were directly related to community norms . Although blunts smoking and use of other forms of marijuana may be seen as different practices , medical marijuana dispensaries might increase availability and ease of access to marijuana. Also, medical marijuana dispensaries may indirectly affect general acceptability of marijuana in the community.
The present study focuses on the associations between availability of tobacco products for blunts and social factors including neighborhood demographics, community-level marijuana use, medical marijuana policy and access to medical marijuana dispensaries and delivery services.This study used data from access surveys conducted at 1,000 tobacco outlets in 50 California cities with populations between 50,000 and 500,000. The sampling procedures for the 50 cities are described elsewhere in detail . This sample was a purposive geographic sample intended to maximize validity with regard to the geography and ecology of the state. Twenty randomly selected tobacco outlets in each city were surveyed. The sampling procedures for the tobacco outlets and survey procedures are also described in detail . In each city, data for the study were available for between 14 and 20 outlets . The selected tobacco outlets in each city were surveyed by two research assistants. At each outlet, a single research assistant attempted to purchase a pack of cigarettes and conducted a brief observation. After leaving the outlet, the research assistants recorded outlet data on a standardized form including whether blunt cigars, small cigars or cigarillos and blunt wrappers were for sale. Institutional review board approval was obtained prior to study implementation.Adult prevalence of past year marijuana use in each city was ascertained from 8,807 adults over the age of 18 years old who participated in a general population telephone survey conducted in the same 50 cities . Respondents were surveyed through a computer-assisted telephone interview. Listed addresses and telephone numbers obtained from various sources were used to develop a sample for the study. Listed samples of phone numbers is unbiased relative to random digit dialing techniques . Respondents were asked if they ever, even once, used marijuana or hashish. Respondents who had used marijuana or hashish were then asked about the number of days in the past 12 months they used marijuana or hashish. Those who reported never using marijuana or hashish or not doing so in the past 12 months were assigned a value of 0. All the others were assigned the value of 1. Adult prevalence of past year marijuana use was computed as the percent of past 12 month marijuana or hashish users in each city. Because of the skewed distribution, this variable was log10 transformed for analyses.Although California allows medical marijuana use, the state leaves regulations regarding the distribution of medical marijuana to patients up to local jurisdictions. Some localities have banned the distribution of marijuana through storefront dispensaries, have strict regulations on cultivation sites, have density restrictions on dispensaries, or some combination. Between June 2012 and July 2012, local city ordinances and policies around distribution and cultivation of marijuana were reviewed to determine whether the city permitted medical marijuana dispensaries or private cultivation in its jurisdiction. Cities were coded as allowing or not allowing medical marijuana storefront dispensaries and/or private cultivation within city boundaries.The density of medical marijuana dispensaries and delivery services is a measure of physical availability of medical marijuana in each of the 50 cities. Delivery services are an alternative means for users to obtain medical marijuana. These services can be available in any of the 50 cities, but are often more available in cities that do not allow distribution through dispensaries. Locations of storefront dispensaries and delivery service areas were obtained from seven different websites listing the information for these businesses in March – April 2012.