Zinc Acetate

Scientists made a single-molecule transistor using quantum interference to control electron flow. This new design offers high on/off ratio and stability, potentially leading to smaller, faster, and more energy-efficient devices. Quantum interference also improves the transistor's sensitivity to voltage changes, further boosting its efficiency. An international team of researchers from Queen Mary University of London, the University of Oxford, Lancaster University, and the University of Waterloo have developed a new single-molecule transistor that uses quantum interference to control the flow of electrons. The transistor, which is described in a paper published in the Nature Nanotechnology, opens new possibilities for using quantum effects in electronic devices. Transistors are the basic building blocks of modern electronics. They are used to amplify and switch electrical signals, and they are essential for everything from smartphones to spaceships. However, the traditional method of making transistors, which involves etching silicon into tiny channels, is reaching its limits. As transistors get smaller, they become increasingly inefficient and susceptible to errors, as electrons can leak through the device even when it is supposed to be switched off, by a process known as quantum tunnelling. Researchers are exploring new types of switching mechanisms that can be used with different materials to remove this effect. In the nanoscale structures that Professor Jan Mol, Dr James Thomas, and their group study at Queen Mary's School of Physical and Chemical Sciences, quantum mechanical effects dominate, and electrons behave as waves rather than particles. Taking advantage of these quantum effects, the researchers built a new transistor. The transistor's conductive channel is a single zinc porphyrin, a molecule that can conduct electricity. The porphyrin is sandwiched between two graphene electrodes, and when a voltage is applied to the electrodes, electron flow through the molecule can be controlled using quantum interference. Interference is a phenomenon that occurs when two waves interact with each other and either cancel each other out (destructive interference) or reinforce each other (constructive interference). In the new transistor's case, researchers switched the transistor on and off by controlling whether the electrons interfere constructively (on) or destructively (off) as they flow through the zinc porphyrin molecule. The researchers found that the new transistor has a very high on/off ratio, meaning that it can be turned on and off very precisely. Destructive quantum interference plays a crucial role in this by eliminating the leaky electron flow from quantum tunneling through the transistor when it is supposed to be switched off. They also found that the transistor is very stable. Previous transistors made from a single molecule have only been able to demonstrate a handful of switching cycles, however this device can be operated for hundreds of thousands of cycles without breaking down. "Quantum interference is a powerful phenomenon that has the potential to be used in a wide variety of electronics applications," said lead author Dr James Thomas, Lecturer in Quantum Technologies at Queen Mary. "We believe that our work is a significant step towards realizing this potential." "Our results show that quantum interference can be used to control the flow of electrons in transistors, and that this can be done in a way that is both efficient and reliable," said co-author Professor Jan Mol. "This could lead to the development of new types of transistors that are smaller, faster, and more energy-efficient than current devices." The researchers also found that the quantum interference effects could be used to improve the transistor's subthreshold swing, which is a measure of how sensitive the transistor is to changes in the gate voltage. The lower the subthreshold swing, the more efficient the transistor is. The researchers' transistors had a subthreshold swing of 140 mV/dec, which is better than subthreshold swings reported for other single-molecule transistors, and comparable to larger devices made from materials such as carbon nanotubes. The research is still in its initial stages, but the researchers are optimistic that the new transistor could be used to create a new generation of electronic devices. These devices could be used in a variety of applications, starting from computers, smartphones, and ending with medical devices.

Researchers evaluated the prevalence, concentration and tissue distribution of essential and non-essential trace elements, including heavy metal toxicants in tissue (blubber, kidney, liver, skeletal muscle, skin) and fecal samples collected from 90 whales and dolphins stranded in Georgia and Florida from 2007 to 2021. Whales and dolphins get their nutrients and essential elements through their diet. While eating fish, squid, octopus, crustaceans and other marine mammals, they are also exposed to heavy metal contaminants. Elevated levels of toxins have been found in stranded dolphins and whales along the Southeastern Coast of the United States. Monitoring toxic contaminants in these stranded marine animals, which serve as important sentinels of environmental contamination, and whose health may be linked to human health, is vital. Yet, data remain sparse on how specific elements are distributed within an animal's body, especially for many rarely encountered species, and how toxicant levels relate to its sex, breed, age and other demographic factors. A study led by Florida Atlantic University's Harbor Branch Oceanographic Institute in collaboration with a team of scientists, evaluated the prevalence, concentration and tissue distribution of essential and non-essential trace elements, including heavy metal toxicants in tissue (blubber, kidney, liver, skeletal muscle, skin) and fecal samples collected from 90 whales and dolphins stranded in Georgia and Florida from 2007 to 2021. Researchers analyzed 319 samples from nine species for concentrations of seven essential (cobalt, copper, iron, manganese, molybdenum, selenium, zinc) and five non-essential (arsenic, cadmium, lead, mercury, thallium) elemental analytes. Species in the study all occupied high and similar trophic levels and consumed a mixture of cephalopods and fishes. Results of the study, published in the journal Cell Press: Heliyon, showed that Risso's dolphins (Grampus griseus) and short-finned pilot whales (Globicephala macrorhynchus) had the highest median concentrations of mercury, cadmium and lead, while dwarf sperm whales (Kogia sima) had the lowest. Adult pygmy and dwarf sperm whales that stranded during 2019 to 2021 had higher concentrations of arsenic, copper, iron, lead, manganese, selenium, thallium and zinc compared to those that stranded during 2010 to 2018, suggesting an increasing risk of exposure over time. "When we separated phylogenetic groups into age classes and compared median concentrations of heavy metals in specific tissue types between adult specimens of species, we found some interesting trends," said Annie Page, D.V.M., Ph.D., senior author, an associate research professor and clinical veterinarian, FAU Harbor Branch. The highest concentrations of many elements (e.g., cadmium, cobalt, copper, manganese, molybdenum, thallium, zinc) were in fecal samples, illustrating the usefulness of this non-invasively collected sample. Aside from fecal samples, hepatic or liver tissues had the highest concentrations of iron, manganese, mercury, molybdenum and selenium in most species; renal or kidney tissues had the highest concentrations of cadmium; skin had the highest concentrations of zinc; and copper, arsenic and lead concentrations were primarily distributed among the liver and kidneys. The lowest median concentrations of mercury and cadmium were in liver, kidney, blubber and muscle samples, with the lowest skin mercury concentration and the lowest liver lead concentration all from dwarf sperm whales. Mercury is one of the most toxic elements in marine systems and can bioaccumulate and biomagnify through marine food webs. Cetaceans are exposed to mercury and other toxic metals mostly by consuming contaminated prey items, which tend to accumulate mercury in liver, muscle and other tissues over time. "Exposure to heavy metal contaminants can result in oxidative stress, which can impair protein function, damage DNA and disrupt membrane lipids," said Page. "Heavy metal exposure has been linked to degenerative heart disease, immunodeficiency and increased parasite infestations, among other disease risks." Findings from the study provide important baseline data needed to further assess the pathophysiological mechanisms and ecotoxicological hazards associated with exposure to and accumulation of trace elements in tissues of free-ranging whales and dolphins. "Because tissue concentrations of heavy metal contaminants also vary based on an individual animal's sex, age class, trophic level and location, among other factors, it is important to first establish baseline values and then continue to monitor cetacean populations for exposure to these toxicants," said Page. Species examined in the study were pygmy sperm whales (Kogia breviceps); dwarf sperm whales; Gervais' beaked whales (Mesoplodon europaeus); Risso's dolphins; short-finned pilot whales; sperm whales (Physeter macrocephalus); melon-headed whales (Peponocephala electra); a Blainville's beaked whale (Mesoplodon densirostris); and a false killer whale (Pseudorca crassidens). Study co-authors represent FAU Harbor Branch; the U.S. Coast Guard Academy; University of Alabama at Birmingham; Hubbs-Sea World Research Institute; Blue World Research Institute; Florida Fish & Wildlife Conservation Commission, Fish & Wildlife Research Institute; and the Georgia Department of Natural Resources. This work was supported by the Florida State License Plate Program "Protect Wild Dolphins" and "Protect Florida Whales" grants (administered by the Harbor Branch Oceanographic Institute Foundation); the Link Foundation; the John H. Prescott Marine Mammal Rescue Assistance Grant; SeaWorld Busch Gardens Conservation Fund; Discover Florida Ocean's License Plate; and the Brevard County Tourism and Development Council.