fox, chicken, and bag of grain
A river crossing puzzle is a type of puzzle in which the object is to carry items from one river bank to another, usually in the fewest trips. The difficulty of the puzzle may arise from restrictions on which or how many items can be transported at the same time, or which or how many items may be safely left together.
52 billion disposable face masks were produced in 2020 (this includes N95 respirators and surgical masks)
It’s estimated that 1.6 billion of these masks ended up in our oceans
This equates to roughly 5,500 tons of plastic pollution
Despite their single-use nature, disposable masks are expected to take more than four centuries to decompose while in the ocean. Here’s how this compares to other items we use on a day-to-day basis.
Years Needed to Biodegrade for items
450 Disposable masks
450 Disposable diaper
450 Plastic bottle
200 Aluminum can
50 Styrofoam cup
20 Plastic grocery bag
10 Cigarette butt
When the underlying quantity is a count, the cumulative curve is technically a step function, but it is usually shown as a continuous curve by connecting each day's cumulative total. A cumulative curve for many days (more than 40) often looks smooth, so you can describe its shape by using the following descriptive terms:
When the number of new “data measured” is increasing, the cumulative curve is "concave up." In general, a concave-up curve is U-shaped, like this: ∪. Because a cumulative frequency curve is nondecreasing, it looks like the right side of the ∪ symbol.
When the number of new “data measured” is staying the same, the cumulative curve is linear. The slope of the curve indicates the number of new cases.
When the number of new “data measured” is decreasing, the cumulative curve is "concave down." In general, a concave-up curve looks like an upside-down U, like this: ∩. Because a cumulative frequency curve is nondecreasing, a concave-down curve looks like the left side of the ∩ symbol.
There is substantial evidence that contaminated air can result in disease spread, and that the combination of air filtration and recirculation can reduce this risk. Observational and animal studies suggest that air recirculation alone may result in the airborne transmission of pathogens.
Waiting for a contaminant to decay naturally in the building is a slow process. Hence, engineering alternatives like mixing indoor air with the outside air and recirculating it back to the room and pressurization control are utilized. There are two types of general air systems: (1) single pass and (2) recirculating. The single pass air system supplies air from the outdoors, and after passing through the room air it is then exhausted 100% back to the outdoor environment. This system does not, however, take advantage of the embodied energy required for heating/cooling of discharged air. In the recirculating system, however, a limited portion of the air is exhausted to the outdoors and replaced by fresh air. Recirculating systems are typically designed for significantly larger flow rates compared to single pass systems as they utilize the power of contaminant dilution. Recirculation could be used as long as air is filtered through high efficiency filters or is cleaned by disinfection techniques. Recirculation of air can be problematic under two conditions: (1) when it leads to the delivery of insufficient fresh air, and consequently excessive CO2exposure, or (2) when the return air is not properly filtered.
The combination of HEPA filtration and air recirculation has been shown to be extremely effective in many space functions such as ORs, AIIRs, and PEs. These systems clean air by simultaneously removing (i.e., filtering) and diluting (through recirculation) contaminants from the space. They have shown significant reduction in the number of bacterial colonies, and surrogate particulate matters previous studies, and they are expected to show a similar efficiency for the COVID-19 pandemic.
The coronavirus outbreak has severely hit the healthcare settings. Notably, in hospitals in the epicenter of the pandemic during the spring of 2020 (New York, Connecticut, and Boston), the surge capacity exceeded standard room configurations and SARS-CoV-2 positive patients were placed in general patient wards and converted ICUs without negative pressure capacity. These spaces likely frequently lack sufficient filtration requirements, ventilation rates, and negative pressurization capacity. Therefore, one short-term solution seems to be substituting the existing filter in those rooms with higher efficiency filters (i.e., HEPA filters). Though this seems like a logical decision at the first glance, it may result in unfavorable outcomes such as increasing the pressure drop when replacing a lower rate filter with HEPA filters. When the pressure drop increases and the fan speed remains constant, the amount of air supplied to the space will decrease. This can result in an imbalanced system that can increase the distribution to spread disease.
The recommendation to use an N95 respirator to reduce the impact of a chemical gas exposure is comparable to the use of a placebo in patient care. Any improvements in conditions are only perceived and are not real.
N95 respirators use a filter of densely woven fibers that can stop aerosol particles through impaction, interception and diffusion as the air being breathed in passes the mesh. They are 95 percent efficient in stopping particles down to about 0.1 micrometers (microns) in diameter. So they work well on tuberculosis, and other bacteria, that range in size from about 0.3 to 20 microns.
Gas molecules, however, range in size from only 0.0003 - 0.006 microns [0.3nm - 60nm]. As a result, gases like oxygen, chlorine, hydrogen sulfide and ammonia can all pass freely in the spaces between the fibers in an N95 mask.
Whilst size comparisons between viruses and bacteria can be useful to researchers, it is also useful to compare the size of SARS-CoV-2 to other things that are encountered daily. For example, a dust mite is typically 200 µm in size. If we take a 100 nm SARS-CoV-2 particle, this makes the dust mite 2000 times larger
For example, respiratory droplets are typically 5-10 micrometers (µm) in length; therefore, it can be inferred that an individual who ingests, inhales, or is otherwise exposed to SARS-CoV-2 positive respiratory droplets can be exposed to hundreds or thousands of virus particles which increases the probability of infection
Difference Between Micron and Nanometer
1 micron = 1 μm = 10-6 m
1 micron = 1/1000 mm
1 nanometer = 1 nm = 10-9m
1 nm = 1/1000 μm
The average human cannot see anything smaller than 40 microns in size. A strand of human hair is around 75 microns or 75,000 nanometers in diameter; human red blood cell is about 6.2 – 8.2 microns or 6,200 – 8,200 nm across; the size of bacteria is about 1,000 nanometers or 1 micron.
There are many NPH assessing scales, most of which aim to assess (1) level of general activity, (2) severity of respective NPH symptoms, (3) response to interventions such as cerebrospinal fluid (CSF) drainage tests or shunt surgery, and (4) short- and long-term outcome. More recently, the caregiver burden is also being assessed. The requirement of any grading scale should be to clearly define each symptom and be highly reproducible by different observers. They should be able to detect the degree of change in symptoms following interventions such as CSF drainage or CSF shunt surgery. Most assessment scales are qualitative and some are quantitative. The criticism leveled against qualitative assessments is that, although clinically useful, each grade of the scale might not span a similar interval, that the scale itself might exhibit inter-observer difference, and that data are not normalized. In contrast, while quantitative assessments are objective, they may reflect a limited part of NPH symptomatology. It is clear that comparative studies of various grading scales are necessary.
Modified Rankin Scale
