Tag Archives: police

‘Potalyzer’ for roadside sobriety tests

Given the drive to legalize marijuana in Canada and in the US and the current crop of marijuana dispensaries in Vancouver (if nowhere else), this new ‘potalyzer’ test from Stanford University (California, US) seems quite timely and destined for popularity in police departments everywhere. From a Sept. 13, 2016 news item on Nanowerk,

This November [2016], several states will vote whether to legalize marijuana use, joining more than 20 states that already allow some form of cannabis use. This has prompted a need for effective tools for police to determine on the spot whether people are driving under the influence. Cars stopped while police interview drivers

Stanford researchers have devised a potential solution, applying magnetic nanotechnology, previously used as a cancer screen, to create what could be the first practical roadside test for marijuana intoxication.

While police are trying out potential tools, no device currently on the market has been shown to quickly provide a precise measurement of a driver’s marijuana intoxication as effectively as a breathalyzer gauges alcohol intoxication. THC, the drug’s most potent psychoactive agent, is commonly screened for in laboratory blood or urine tests – not very helpful for an officer in the field.

The Stanford device might function as a practical “potalyzer” because it can quickly detect not just the presence of THC in a person’s saliva, but also measure its concentration.

A Sept, 8, 2016 Stanford University news release by Carrie Kirby, which originated the news item, describes the technology in a little more detail,

Led by Shan Wang, a professor of materials science and engineering and of electrical engineering, the Stanford team created a mobile device that uses magnetic biosensors to detect tiny THC molecules in saliva. Officers could collect a spit sample with a cotton swab and read the results on a smartphone or laptop in as little as three minutes.

Researchers tackling the “potalyzer” problem have zeroed in on saliva because testing it is less invasive and because THC in saliva may correlate with impairment better than THC in urine or blood. The big challenge is that these spit tests may be called upon to detect superlatively tiny concentrations of THC. Some states have no set limit of THC in the body for drivers, while others set a limit of 0 or 5 nanograms (a billionth of a gram) per milliliter of blood.

Wang’s device can detect concentrations of THC in the range of 0 to 50 nanograms per milliliter of saliva. While there’s still no consensus on how much THC in a driver’s system is too much, previous studies have suggested a cutoff between 2 and 25 ng/mL, well within the capability of Wang’s device.

Repurposing biomedical tools

The researchers achieved such precision by harnessing the behavior of magnetism in nanoparticles, which measure just a few tens of billionths of a meter.

The Wang Group has been exploring magnetic nanotechnology for years, using it to attack such diverse problems as in vitro cancer diagnostics and magnetic information storage. In this case, they’re combining magnetic nanotechnology with the time-tested biochemical technique of the immunoassay. Immunoassays detect a certain molecule in a solution by introducing an antibody that will bind only to that molecule.

In the test, saliva is mixed with THC antibodies, which bind to any THC molecules in the sample. Then the sample is placed on a disposable chip cartridge, which contains magnetoresistive (GMR) sensors pre-coated with THC, and inserted into the handheld reader.

This sets in motion a “competition” between the THC pre-coated on the sensor and THC in the saliva to bind with the antibodies; the more THC in the saliva, the fewer antibodies will be available to bind to the THC on the sensor surface.

The number of antibodies bound to THC molecules on the sensor tells the device how many antibodies the THC in the sample used up, and therefore how many THC molecules were present in the sample.

Next, magnetic nanoparticles, specially made to bind only to the antibodies, are introduced to the sample. Each nanoparticle binds onto a THC-antibody pair like a sticky beacon, but only the molecules on the sensor surface will be close enough to trip the GMR biosensors in the reader. The device then uses Bluetooth to communicate results to the screen of a smartphone or laptop.

“To the best of our knowledge, this is the first demonstration that GMR biosensors are capable of detecting small molecules,” Wang wrote in a paper describing the device, published in Analytical Chemistry.

Beyond marijuana

The platform has potential usefulness beyond THC. Just as they do with THC, the GMR biosensors in the device could detect any small molecule, meaning that the platform could also test for morphine, heroin, cocaine or other drugs.

In fact, with 80 sensors built into it, the GMR biosensor chip could screen a single sample for multiple substances. The team has already tried screening for morphine with promising results.

Students are currently working on creating a user-friendly form factor for the device, which would need to go through field tests and be approved by regulators before it can be deployed by police.

Another thing that would have to happen before the device would be useful to law enforcement: State laws must set limits for the concentration of THC allowed in a driver’s saliva.

Here too, the Wang Group’s device could be helpful. For example, the next generation of the device could screen both the blood and saliva of a subject to establish an understanding of the correlation between blood THC level and saliva THC level at the same degree of intoxication.

Here’s a link to and a citation for the paper,

Small Molecule Detection in Saliva Facilitates Portable Tests of Marijuana Abuse by Jung-Rok Lee, Joohong Choi, Tyler O. Shultz, and Shan X. Wang. Anal. Chem., 2016, 88 (15), pp 7457–7461 DOI: 10.1021/acs.analchem.6b01688 Publication Date (Web): July 19, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

Curbing police violence with machine learning

A rather fascinating Aug. 1, 2016 article by Hal Hodson about machine learning and curbing police violence has appeared in the New Scientist journal (Note: Links have been removed),

None of their colleagues may have noticed, but a computer has. By churning through the police’s own staff records, it has caught signs that an officer is at high risk of initiating an “adverse event” – racial profiling or, worse, an unwarranted shooting.

The Charlotte-Mecklenburg Police Department in North Carolina is piloting the system in an attempt to tackle the police violence that has become a heated issue in the US in the past three years. A team at the University of Chicago is helping them feed their data into a machine learning system that learns to spot risk factors for unprofessional conduct. The department can then step in before risk transforms into actual harm.

The idea is to prevent incidents in which officers who are stressed behave aggressively, for example, such as one in Texas where an officer pulled his gun on children at a pool party after responding to two suicide calls earlier that shift. Ideally, early warning systems would be able to identify individuals who had recently been deployed on tough assignments, and divert them from other sensitive calls.

According to Hodson, there are already systems, both human and algorithmic, in place but the goal is to make them better,

The system being tested in Charlotte is designed to include all of the records a department holds on an individual – from details of previous misconduct and gun use to their deployment history, such as how many suicide or domestic violence calls they have responded to. It retrospectively caught 48 out of 83 adverse incidents between 2005 and now – 12 per cent more than Charlotte-Mecklenberg’s existing early intervention system.

More importantly, the false positive rate – the fraction of officers flagged as being under stress who do not go on to act aggressively – was 32 per cent lower than the existing system’s. “Right now the systems that claim to do this end up flagging the majority of officers,” says Rayid Ghani, who leads the Chicago team. “You can’t really intervene then.”

There is some cautious optimism about this new algorithm (Note: Links have been removed),

Frank Pasquale, who studies the social impact of algorithms at the University of Maryland, is cautiously optimistic. “In many walks of life I think this algorithmic ranking of workers has gone too far – it troubles me,” he says. “But in the context of the police, I think it could work.”

Pasquale says that while such a system for tackling police misconduct is new, it’s likely that older systems created the problem in the first place. “The people behind this are going to say it’s all new,” he says. “But it could be seen as an effort to correct an earlier algorithmic failure. A lot of people say that the reason you have so much contact between minorities and police is because the CompStat system was rewarding officers who got the most arrests.”

CompStat, short for Computer Statistics, is a police management and accountability system that was used to implement the “broken windows” theory of policing, which proposes that coming down hard on minor infractions like public drinking and vandalism helps to create an atmosphere of law and order, bringing serious crime down in its wake. Many police researchers have suggested that the approach has led to the current dangerous tension between police and minority communities.

Ghani has not forgotten the human dimension,

One thing Ghani is certain of is that the interventions will need to be decided on and delivered by humans. “I would not want any of those to be automated,” he says. “As long as there is a human in the middle starting a conversation with them, we’re reducing the chance for things to go wrong.”

h/t Terkko Navigator

I have written about police and violence here in the context of the Dallas Police Department and its use of a robot in a violent confrontation with a sniper, July 25, 2016 posting titled: Robots, Dallas (US), ethics, and killing.

Isotopes, beverages, and nuclear isotope shortages

Nanowerk recently posted a news item about isotopes and beverages which indicates that scientists can track your geographic location because the beverages you drink leave a signature or trace  in your hair. From the news item,

The scientists analyzed isotope patterns in bottled water, soda pop, and beer from 33 cities and found that patterns in the beverages generally matched those already known for the tap water. They noted that the isotope pattern in beverages tends to vary from city to city in ways that give cities in different regions characteristic “iso-signatures.” A person who drinks a beer or soda in Denver, Des Moines, or Dallas, for instance, consumes a different isotope signature than a person in Las Cruces, Las Vegas, or Laramie. The finding may help trace the origin of drinks or help criminal investigators identify the geographic travels of crime suspects and other individuals through analysis of hair strands, the study suggests.

I think Sherlock Holmes would have liked this. On another note, for anyone (like me) who’s not quite sure what an isotope is, I found a number of definitions and this one best fits the use described in the news item,

some elements have more than one form. They differ only in nuclear terms rather than chemical ones and have different relative atomic mass as a result. They may behave slightly differently which allows us to use them in geography for a number of measurements relating to constructing past conditions. http://www.tuition.com.hk/geography/i.htm

On other isotopic fronts, Dave Bruggeman at Pasco Phronesis posted about a move by the Government of British Columbia (a Canadian province) to address the shortage of medical isotopes. There was a bit of a scandal last year when Canadians found out that the Chalk River facility which produces a fair chunk (1/3 according to this Wikipedia essay) of the global supply of  isotopes used for medical purposes was badly deteriorating.

There have been a number of problems with the facility since 2007 culminating in a shutdown in 2009 which helped to precipitate a worldwide shortage and a Canadian scandal. The Chalk River facility has yet to reopen but (from Pasco Phronesis),

… The B.C. Premier recently announced that a $63 million (Canadian) accelerator facility will be developed at the national physics lab [TRIUMF] in Vancouver (H/T Science Canada). The use of an accelerator for generating isotopes is critical, as it’s a relatively new means for doing so. It allows for a means to move away from using fission reactors for isotope generation.

Bravo Premier Campbell! Margaret Munro in her June 23, 2010 article about the initiative noted in the Vancouver Sun,

Premier Gordon Campbell, who handed over $30.7 million for the project, talked up the more down-to-earth benefits, such as helping alleviate the global medical-isotope shortage, and demonstrating that B.C. is home to “world-class ” science and groundbreaking technology.

The new accelerator promises “a new way to produce the radio isotopes needed by doctors and patients everywhere,” Campbell said.

The provincial money means construction can begin this summer on the powerful accelerator that is expected to beam Canada into the forefront of subatomic and isotope research. The Canada Foundation for Innovation has invested $18 million, and $14 million will come from core federal funding for TRIUMF.

Isotopes, used for medical scans and treatments, are now made by aging and increasingly unreliable nuclear reactors [Chalk River]. Researchers at TRIUMF are working with teams across Canada to explore new options.

This doesn’t sound like the same kind of isotope the chemists were talking about with the beverages and the discussion of geographic tracking. If I understand the difference rightly, the isotopes in the beverages are naturally occurring while these other isotopes are engineered and, I imagine, less stable. For anyone who loves definitions, here’s another one for isotopes,

an atom that has more neutrons in the nucleus than its stable counterpart. For example: Hydrogen has one electron and a nucleus containing one proton, Deuterium (an isotope of hydrogen) has one electron plus a nucleus containing one proton and one neutron. www.hiper-laser.org/glossary.asp