Know your security detectors, including the hidden ones

The technology that goes into detecting people armed with weapons and drugs in  modern Airports are getting more sophisticated. Airport security uses a host of tools from the handheld wands, the step through metal detectors or the Backscatter X-ray machines not to mention possible hidden ones. Metal detectors use  three technologies Very low frequency (VLF), Pulse induction (PI) and Beat-frequency oscillation (BFO).

If the Pulse induction metal detector is over a metal object, the pulse creates an opposite magnetic field in the object. When the pulse's magnetic field collapses, causing the reflected pulse, the magnetic field of the object makes it take longer for the reflected pulse to completely disappear. This process works something like echoes: If you yell in a room with only a few hard surfaces, you probably hear only a very brief echo. This type of metal detector is normally associated with step through detectors.
security sensitive areas have began using a device that scans the whole body for contraband. The scan produces an imagine of the skin, and will show objects like guns, drugs, other weapons under clothing. This procedure is often used an alternative to whole body strip searches. The device uses a low energy x-ray or gamma source to produce the image. X-rays come in many flavors from hard to soft with hard being the most penetrating. All x-rays are ionizing radiation this means the x-ray photons break DNA, chemical bonds by dislodging electrons and generate destructive free radicals. Backscatter x-ray uses the Compton Effect to reflect or scatter x-rays back to detectors.

Backscatter x-ray systems use a complex mechanical assembly to sweep an intense pencil beam of x-rays head to toe. The x-rays leave a trail of damaged DNA and cells from head to toe. Most x-ray are absorbed by the body tissue a small fraction is back-scattered or reflected like a window back to special detectors. The twelve year old fuzzy public images below reveal a great deal. If you inspect the lower leg and arms of the man shown you will see "bone shadows". This is a result of the x-rays penetrating the skin and being absorbed by the underlying bones, the same shadow is seen on the top of the head showing the skull. Fewer x-rays are being "back scattered" from the bone making this region dark in the image. Clearly the x-rays penetrate the skin and reach bones and deeper radio sensitive tissues such as ovary, testicles. thyroid, breast and eyes.

To put the radiation dose received into perspective:
Naturally occurring ionizing radiation is all around us. We are continuously exposed to this background radiation during ordinary living. In 42 minutes of ordinary living, a person receives more radiation from naturally occurring sources than from screening with any general-use x-ray security system.
The national radiation safety standard (see below) sets a dose per screening limit for the general-use category. To meet the requirements of the general-use category a full-body x-ray security system must deliver less than the dose a person receives during four minutes of airline flight. TSA has set their dose limit to ensure a person receives less radiation from one scan with a TSA general-use x-ray security system than from two minutes of airline flight. A person would have to be screened more than a thousand times in one year to exceed the annual radiation dose limit for people screening that has been set by expert radiation safety organizations.

Emerging THz technological applications,THz waves are found between microwaves and infrared on the electromagnetic spectrum. This type of radiation was chosen for security devices because it can penetrate matter such as clothing, wood, paper and other porous material that’s non-conducting. The terahertz spectrum is so good for scanning; infrared cameras can see through some obstacles. The effect is even more pronounced with the lower wavelength terahertz radiation.
This type of radiation seems less threatening because it doesn’t penetrate deeply into the body and is believed to be harmless to both people and animals. THz waves may have applications beyond security devices. Research has been done to determine the feasibility of using the radiation to detect tumors underneath the skin and for analyzing the chemical properties of various materials and compounds. The potential marketplace for THz driven technological applications may generate many billions of dollars in revenue.
The past several years the possible health risks from cumulative exposure to THz waves was mostly dismissed. Experts pointed to THz photons and explained that they are not strong enough to ionize atoms or molecules; nor are they able to break the chains of chemical bonds. They assert—and it is true—that while higher energy photons like ultraviolet rays and X-rays are harmful, the lower energy ones like terahertz waves are basically harmless. While that is true, there are other biophysics at work. Some studies have shown that THZ can cause great genetic harm, while other similar studies have shown no such evidence of deleterious affects.
A company called Genia Photonics has developed a programmable picosecond laser that is capable of spotting trace amounts of a variety of substances. Genia claims that the system can detect explosives, chemical agents, and hazardous biological substances at up to 50 meters. This is why the US Department of Homeland Security is so keen on getting it into airports.
This device relies on classic spectroscopy; just a very advanced form of it. A spectrometer is simply a device that uses radiated energy to characterize a material. In the case of Genia’s scanner, it is using far-infrared radiation in the terahertz band. It’s important to understand that this is not an imaging device, but a tool for reading absorbance spectra (in this case it is a very sensitive electronic nose). Some of the radiation emitted will be absorbed by everything (and everyone) it is directed at. Because different compounds absorb that energy in different ways, the profile of energy returned to the scanner can tell you what it “saw.”
This kind of picosecond laser reads the environment in real-time. That gunpowder residue on your hand from hunting the other day, cannabis smoke particles in your hair, or even a bit of (explosive-boosting) nitrate fertilizer stuck to your shoe could trigger this scanner. Perhaps this invasive technology might replace the pat down option or even the x-ray and the terahertz body scanners. In future this technology could be a key device to detect improvised bomb devices or a suspicious criminals for gun powder or drug traces. Perhaps another gadget for law enforcement in the not so distant future...

Space, the health issue

Like it or not people out there think the next big thing is space travel or exploration, I mentioned this about how they are building a space port for potential space tourists. Its already decided and that people are making this happen, it stands to reason that we kind of need the full facts of exposure to space. I like the fact when you go from an environment with gravity enriched with oxygen and nitrogen mix. You need technology to allow you to exist in the extreme environment of space.

Potentially the success space tourism will allow pave the way to factories in space and mining colonies on other worlds. Soviet Union is already investigating space manufacturing with its Soyuz space-lab station. The unique environment of space could potentially provide excellent conditions of a hard vacuum and micro gravity. Growth of crystals, improved semiconductor wafers and micro encapsulation are considered early candidates. Though most electronics and pharmaceutical companies, don't have a space program. It is likely that the commercial space program will attract investors who might have links with manufactures seeking to expand.

The effect of space on the human body comes immediately, human beings are equipped  various mechanisms to oppose gravity to maintain sufficient blood flow to the brain. In a micro gravity environment, the distribution of body fluid alters since it is free from gravitational effects. This fluid shift symptoms are stuffy nose and headaches.

Bones are systems that are involved in the maintaining posture. The adult body has 1 kilo to 1.2 kilos of calcium and 400 to 500 of phosphorus. however once gravitational stress is removed, the  body excessively excretes bone calcium and phosphorus through urine and faeces. It seems that 3.2% of average bone loss occurred after nearly 10 days of weightlessness. To countermeasure this massive bone loss it is recommended that regular exercise with the treadmill and ergo meter.

The effects of space on muscle can rapidly deteriorate or cause muscle atrophy, due to lack of use in a gravity free environment. Simple maneuvers, such as walking across the room can be easily executed by pushing  a wall and floating by the area you want.
Significantly alteration in the hematologic system in micro gravity is the transformation of red blood cells, the main component of blood. Blood cells change shape from a bioconcave discoid shape, to a spherical shape. however it can be reversed even after long term space missions once returned to the Earth.

Radiation commonly exist in a space environment. On Earth we are protected by a magnetic field and a thick atmosphere. Due to the absence of this shielding in a space environment, astronauts are exposed to large amounts of cosmic rays and any stray particles (mostly protons). Nasa have ideas to shield low to medium energy rays using hydrogen rich plastics. Also water could be another material to shield astronauts, in extreme space conditions or solar wind activity.
Contradictory to the harmful effects of space exposure to muscle and cardiovascular systems, Dr Nathaniel Szewczyk at the University of Nottingham found that microscopic worms left out in the International space station for over 9 years after returning to earth have lived longer then the control group who stayed in the labs. He has found microgravity lowered buildup of toxic proteins in aging muscles, also genes related to controlling metabolic rates a have been lowered. It is said that the worms have adapted to the change in its environment and can be seen as space-flight slows the process of aging.

With positive and negative points of long term exposure to space-flight I am incline to believe that space tourism might be a flight of fancy. And that more research is needed to find the health factors in long term missions. Though if longevity can be sustained in humans it might be an answer for people who are rich enough to have a health care hospital orbiting the Earth. My own thoughts are that space will bring a future that will broadly change the industry through manufacturing and mining for new materials. I have a suspicion that Tourism will help build a infrastructure of industry and that it will spawn new factories in space for the electronics and pharmaceutical companies. But I also think the heath issues of space travel needs to be addressed with proper shielding. Without this there is a high risk of ration sickness or cancer, such exposure might call for hazard pay.