Abstract: The subject invention provides materials and methods for detecting Zika virus. Specific embodiments provide an electrochemical immunosensing device and the methods of making and using the same for detecting Zika virus with exceptionally low detection limit. In some embodiments, the immunosensing device is capable of detecting picomolar (pM) level of Zika virus present in a sample by employing immunosensors functionalized with Zika virus binding ligands such as monoclonal Zika virus antibodies and Zika non-structural proteins. In an exemplary embodiment, the immunosensing device can be integrated with microelectronics to be adopted as point-of-care sensing systems. Advantageously, technologies provided herein offer rapid, on-site biosensing methods for the accurate detection of diseases caused by Zika virus.

Abstract: A new magnetic carbon nanotube (mCNT) biosensor ink (mbio-ink) that utilizes immobilized capture agents to detect specific target analytes via a simple current response method is presented here, expanding the applications of magnetic carbon nanotubes as biomolecule-sensing nanomaterials. The employment of a magnetic field to print the mbio-ink into electrically conductive networks facilitates its integration with an external circuit via the use of a simple electrode system. When the sensor is connected to an external power source, the reduction in current, caused by an interaction between the capture agents and target analyte, is detected. The rapid detection technique and generic benchtop fabrication method allows for scale up, while the small volumes required and magnet independent electrical measurements renders the mbio-ink attractive for drug screening and disease detection applications.

Abstract: An impedance based biosensor and method for detecting a target biomolecule in a sample are provided. The biosensor has a substrate, and first and second spaced-apart electrodes disposed at the substrate. A molecular recognition element (MRE) for binding with the target is bound to the substrate between the first and second electrodes. The biosensor also has a nanoparticle having an MRE bound to its surface. In the presence of the target, the nanoparticle is immobilized between the first and second electrodes due to binding of the target biomolecule with the first MRE and binding of the target biomolecule with the second MRE. A measurable change in electrical impedance across the first and second electrodes occurs due to the immobilization of the nanoparticle between the first and second electrodes.

Abstract: Disclosed is a cartridge for sample analysis, including a cartridge base body having, formed therein, a chamber configured to store a liquid containing a test substance, and a storage portion which is connectable with the chamber and is configured to store a liquid reagent to be supplied to the chamber, carrier particles immobilized onto an inner wall of the chamber, a first liquid reagent stored in the storage portion, and a first capture substance that specifically binds to the test substance. The carrier particles are immobilized onto the inner wall by means of a solid mixture containing sugar and protein.

Abstract: Devices for detecting biomarkers in a sample and methods for detecting such biomarkers are discussed. The biomarkers may be associated with a particular disease such as breast cancer or another health condition. The devices may contain a disc including a plurality of microfluidic channels extending in a radial direction of the disc, the microfluidic channels pre-loaded with a plurality of capture molecules specific to at least one biomarker. The methods may include introducing a fluid sample into at least one microfluidic channel of a disc, rotating the disc, such that the fluid sample flows radially outward through the at least one microfluidic channel to combine with capture molecules specific to at least one biomarker, and detecting a signal from the disc indicative of a presence of the at least one biomarker contained in the fluid sample.

Abstract: The present invention relates to analyte detection devices and methods of using such devices to detect minute quantities of a target analyte in a sample. In particular, the invention provides a method of detecting a target analyte in a sample comprising mixing the sample with a first detection conjugate and a second detection conjugate in solution, wherein the first and second detection conjugates comprise metallic nanostructures coupled to binding partners that are capable of specifically binding to the target analyte if present in the sample to form a complex between the first detection conjugate, the analyte, and the second detection conjugate, wherein a change in an optical signal upon complex formation indicates the presence of the target analyte in the sample. Methods of preparing nanostructures and nanoalloys, as well as nanostructures and nanoalloys conjugated to binding partners, are also described.

Abstract: An assay method and device can perform at least one (e.g., at least two) assays on a single aliquot of a sample liquid. The device can mix a sample liquid with assay reagents including magnetically susceptible particles. The device is configured to create a sample liquid-air interface with the sample liquid. The magnetically susceptible particles can be located (via an applied magnetic field) at the liquid-air interface when a second liquid contacts the interface to form a liquid-liquid interface. The magnetic particles travel across the liquid-liquid interface to the second liquid. The magnetically susceptible particles are configured to trans-port an analyte across the interface into the second liquid. An assay for the analyte is performed in the second liquid. An assay for another analyte can also be performed in the sample liquid.

Abstract: Devices and methods incorporate mucolytic agents into a point-of-care testing device. The sample is loaded, and then the sample travels until it encounters one or more lysis agents and/or mucolytic agents. The mucolytic agent is preferably pre-loaded onto the collection device. In a preferred embodiment, the mucolytic agent is localized between the sample application zone and the conjugate zone. In embodiments with a sample compressor, one or more mucolytic agents may be pre-loaded and dried on the sample compressor, the sample collector, in various locations on the test strip, or in the running buffer.

Abstract: Disclosed are methods, compositions and kits of detecting or diagnosing Sjogren's syndrome based on the presence of autoantibody against aquaporin 5, which is found in the present disclosure. The present methods, compositions or kits can be advantageously used for accurate, reliable and rapid diagnose of Sjogren's syndrome, which is known to be difficult by conventional methods.

Abstract: Nonwoven articles for detecting microorganisms or cellular analytes in a fluid sample are provided. The nonwoven article includes a fibrous porous matrix and concentration agent particles enmeshed in the fibrous porous matrix. The fibrous porous matrix generally consists of inorganic fibers and polymeric fibers. Methods of detecting microorganisms or cellular analytes in a fluid sample are also provided. The method includes providing the nonwoven article, providing a fluid sample suspected of containing at least one microorganism strain or target cellular analyte, contacting the fluid sample with the nonwoven article such that at least a portion of the at least one microorganism strain or target cellular analyte is bound to the nonwoven article, and detecting the presence of bound microorganism strain(s) or bound cellular analyte(s).

Abstract: A method of distinguishing mesenchymal stem cells (MSCs) from fibroblasts is provided. Also provided is a method of increasing a purity of mesenchymal stem cells (MSCs) population in a cell culture. The above-mentioned methods each comprise a step of sorting or isolating the cells by a marker of CD146 from a cell culture derived from a placenta-related tissue. Further provided is a method of assessing purity of mesenchymal stem cells (MSCs) in a cell culture derived from a placenta-related tissue, comprising determining the percentage of cells expressing CD146 in the culture.

Abstract: Provided is a method and a system for detecting avian influenza virus. More particularly, the method and a system for detecting avian influenza virus based on cell lines, which are capable of identifying avian influenza virus using infection pattern information for the cell lines, which is obtained by patterning a difference in infectivity of each subtype of avian influenza virus for some particular cells.

Abstract: In one aspect, the invention is directed to a method of detecting Cowden syndrome (CS) or CS-like syndrome in an individual comprising detecting the presence of a mutated succinate dehydrogenase B (SDHB), mutated succinate dehydrogenase D (SDHD) or combination thereof in the individual, wherein detection of a mutated SDHB, SDHD or a combination thereof indicates that the individual is positive for CS or CS-like syndrome. In another aspect, the invention is directed to a method of determining whether an individual is at risk for developing Cowden syndrome (CS) or CS-like syndrome comprising detecting the presence of a mutated succinate dehydrogenase B (SDHB), mutated succinate dehydrogenase D (SDHD) or combination thereof in the individual, wherein detection of a mutated SDHB, SDHD or a combination thereof indicates that the individual is at risk for developing for CS or CS-like syndrome.

Abstract: The current disclosure provides methods for detecting and analyzing KRT4 and KRT17 expression in a sample obtained from a test subject. The current disclosure pertains to methods and kits for identifying a mammalian subject with cervical cancer or non-cancerous lesions of the cervix. The current disclosure further provides methods and kits for determining the likelihood of survival or treatment outcome of a subject having cervical cancer by determining the expression level of KRT17 in a sample.

Abstract: Methods are provided for identifying biomarker proteins that exhibit differential expression in subjects with a first lung condition versus healthy subjects or subjects with a second lung condition. Also provided are compositions comprising these biomarker proteins and methods of using these biomarker proteins or panels thereof to diagnose, classify, and monitor various lung conditions. The methods and compositions provided herein may be used to diagnose or classify a subject as having lung cancer or a non-cancerous condition, and to distinguish between different types of cancer (e.g., malignant versus benign, SCLC versus NSCLC).

Abstract: Disclosed is a magnetic nanostructure for detecting and isolating circulating tumor cells including a conductive polymer to which an antibody and magnetic nanoparticles are bound, which enables circulating tumor cells from early cancer patients and various circulating tumor cell types to be effectively detected using a small amount of blood, circulating tumor cells to be monitored with the naked eye through colorimetric detection, and a very small amount of circulating tumor cells present in blood to be efficiently captured with a strong magnetic field generated by a large amount of the loaded magnetic nanoparticles; in detecting, isolating, and collecting the circulating tumor cells in a very small amount, a long nanowire structure and various antibody types are used, whereby contact with cancer cells may be increased and strong bonding may be formed; sensitivity is increased and various interactions with cancer cells are facilitated, thereby exhibiting increased detection and isolation effects.

Abstract: A method of obtaining a population of cells enriched in human polymorphonuclear myeloid derived suppressor cells (PMN-MDSCs) comprises isolating from a cell suspension those cells which express LOX-1 to provide a population of cells enriched with PMN-MDSCs. A method of monitoring the population of LOX-1+ cells in a cell-containing biological sample is useful for determining the efficacy of treatment or the metastasis or increasing progression of cancer. Other cell isolation and diagnostic methods are also described. A composition for use in diagnosing and treating cancer related to PMN-MDSC is provided that contains antagonists and/or inhibitors of genes related to the ER stress response.

Abstract: Analyte detection systems and devices are provided. In one embodiment, a sensor initially reviews an assay, for instance a test strip, to designate a particular testing sequence. The sensor may calibrate the unit and then identify the particular testing sequence by identifying a color indicator on the test strip. The result is systems and methods to improve the detection of the presence and/or absence of at least one analyte in a sample.

Abstract: Methods and compositions are provided that include a multichromophore and/or multichromophore complex for identifying a target biomolecule. A sensor biomolecule, for example, an antibody can be covalently linked to the multichromophore. Additionally, a signaling chromophore can be covalently linked to the multichromophore. The arrangement is such that the signaling chromophore is capable of receiving energy from the multichromophore upon excitation of the multichromophore. Since the sensor biomolecule is capable of interacting with the target biomolecule, the multichromophore and/or multichromophore complex can provide enhanced detection signals for a target biomolecule.

Abstract: Disclosed herein are diagnostic assays using surface enhanced Raman spectroscopy (SERS)-active particles, including liquid-based assays; magnetic capture assays; microparticle-nanoparticle satellite structures for signal amplification in an assay; composite SERS-active particles useful for enhanced detection of targets; and sample tubes and processes for using the same.

Abstract: An apparatus is disclosed comprising a first device for generating aerosol, smoke or vapour from one or more regions of a target, an inlet conduit to an ion analyser or mass spectrometer, the inlet conduit having an inlet through which the aerosol, smoke or vapour passes, and a Venturi pump arrangement arranged and adapted to direct the aerosol, smoke or vapour towards the inlet.

Abstract: The present invention relates generally to assessment of the relative risk of injury of joints. Test kits and methods of diagnosing and monitoring relative risk of joint injury are provided. The apparatus and methods beneficially permit intervention to reduce the risk of joint injury and/or reduce the damage resulting from joint injury. Methods for monitoring recovery from a joint injury are also provided.

Abstract: This invention relates to a method of diagnosing the depression, and more particularly to a method and kit for diagnosing depression after acute coronary syndrome, by measuring the concentration of a specific biomarker in the blood of a patient suffering from acute coronary syndrome to predict depression after acute coronary syndrome.

Abstract: The present invention relates to methods of typing a female subject as being at risk of developing gestational diabetes, comprising determining a level of expression of Secreted Frizzled-Related Protein 4 (sFRP4). The invention further relates to methods of treating of a subject being at risk of developing, gestational diabetes, comprising typing the subject according to the methods of the invention, and treating the subject with a dietary meal plan and/or physical activity. The invention additionally relates to kit for a pregnant female subject for susceptibility to gestational diabetes, use of a kit according to the invention for typing a female subject as being at risk of developing gestational diabetes, and to an antibody specific to sFRP4 for use in a method for determining a risk of a female subject of developing gestational diabetes.

Abstract: The present invention identifies biomarkers that are diagnostic of nerve cell injury and/or neuronal disorders. Detection of different biomarkers of the invention are also diagnostic of the degree of severity of nerve injury, the cell(s) involved in the injury, and the subcellular localization of the injury.

Abstract: Recombinant tissue plasminogen activator (tPA) is a lytic medication in wide use to treat thrombotic disorders such as stroke, myocardial infarction (MI), and pulmonary embolism (PE). It is also used “off-label” for the treatment of deep venous thrombosis (DVT) and acute peripheral arterial thrombosis/embolism. It has been shown in multiple studies that in approximately 25% of the individuals receiving the treatment the drug is ineffective. Start of the tPA treatment for these patients results in delay of start of alternate treatment for these patients which may be life saving for them. In the past there has been no test to find the effectiveness of the treatment and identify the individuals for whom the treatment will be ineffective. What is disclosed is a method of testing for effectiveness of the tPA treatment, that is testing for thrombolytic resistance, using a sample of the individual's blood via coagulation analysis.

Abstract: Embodiments of a blood coagulation testing system can operate as an automated thromboelastometry system that is particularly useful, for example, at a point-of-care site. In some embodiments, the blood coagulation testing system includes a single-use cartridge component configured to measure and mix reagents with blood received from a blood sample reservoir. A mixing chamber in the single-use cartridge includes different reagent beads that, when exposed to a pre-determined volume of blood, dissolve and mix specific reagents with the blood. The assembled blood cartridge further includes configurations that are designed to prevent blood from prematurely mixing with reagent beads in the mixing chamber and to guide blood flow in the mixing chamber to dissolve reagent beads in a desired order. Thus, the mixture obtained from the mixing chamber can be readily utilized to generate results for the blood coagulation testing system.

Abstract: A method of analysis using mass spectrometry and/or ion mobility spectrometry is disclosed comprising: (a) using a first device to generate smoke, aerosol or vapour from a target in vitro or ex vivo cell population; (b) mass analysing and/or ion mobility analysing said smoke, aerosol or vapour, or ions derived therefrom, in order to obtain spectrometric data; and (c) analysing said spectrometric data in order to identify and/or characterise said target cell population or one or more cells and/or compounds present in said target cell population.

Abstract: A method for determining a lipid imbalance in a subject is provided. The method includes providing one or more tape strips comprising a skin surface sample obtained from the subject; extracting epidermal lipids; detecting a composition of lipids present in the extracted sample; and comparing the composition of lipids to a control. A difference in the composition of lipids as compared to the control identifies the lipid imbalance in the subject. A method of augmenting a lipid deficiency in skin of a subject, for example to treat or inhibit infection, prevent water loss, improve hydration and restore barrier is also provided. The method includes identifying a deficiency in one or more lipids in a skin sample obtained from the subject; formulating a topical therapeutic composition that contains the one or more lipids, a similar lipid, or a subset thereof; and providing the composition to the subject. Topical formulations for augmenting a lipid deficiency in the skin of a subject are also disclosed.

Abstract: A home test kit is provided for preparing an extract from herbs, in particular, extracts from medical marijuana that can be sent into an independent lab for testing the presence and concentration of cannabinoids.

Abstract: A system for automated urinalysis includes an in-line sensor disposed in a conduit between a sanitation device such as a toilet and a standard waste treatment system. The sensor may include a matrix of reagent strips. An image of the exposed matrix of reagent strips is captured with a CCD camera. The exposed matrix of reagent strips may be illuminated by an LED in order to facilitate image acquisition. A representation of the image is transmitted to an analysis program. Results of the analysis may be transmitted to a mobile device such as a smart phone.

Abstract: In a detection method, a first pressure within a pipette tip is measured when air is sucked into or expelled from the leading end of the pipette tip in a state where the leading end of the pipette tip and a reference part of a solid are separated. A second pressure within the pipette tip is measured when air is sucked into or expelled from the leading end of the pipette tip in a state where the leading end of the pipette tip and the reference part of the solid are closer than in the first step. After the first step and second step, the position of the leading end of the pipette tip in relation to the reference part is detected on the basis of the difference between the first pressure measured in the first step and the second pressure measured in the second step.

Abstract: Disclosed are fluidics devices and assemblies allowing for fluid flow between a plurality of wells. The fluidics devices and assemblies that are provided mimic in vivo tissue environments by allowing for initially segregated tissue cultures that can then be linked through fluid flow to measure integrated tissue response. The fluidics devices and assemblies provide a pumpless system using surface tension, gravity, and channel geometries. By linking human tissue functional systems to better simulate in vivo feedback and response signals between the tissues, the need for testing in animals can be minimized.

Abstract: A picking instrument for picking biological samples, such as microbial samples, includes a picking pin having a distal tip and three degrees-of-freedom and configured to move in x, y, and z directions. The picking instrument also includes a loading platform comprising a first area and a second area, the first area configured to accommodate and secure a microfabricated chip including a plurality of microwells. The picking pin is programmatically controlled to pick a sample contained in one or more selected microwells of the microfabricated chip and then transfer the sample to a predetermined location at the destination sample holder. Methods of operating the picking instrument, including calibrating the coordinates of the selected microwell(s) relative to a location of the picking pin, are also provided.

Abstract: Disclosed are various embodiments for a berry impact recording device. The berry impact recording device comprises a shell. Within the shell are at least a sensor and an integrated circuit. The sensor may be configured to detect an acceleration of the berry impact recording device. The integrated circuit may be configured to record the acceleration of the berry impact recording device and a timestamp corresponding to the acceleration.

Abstract: A flexible electronic device includes a flexible electronic circuit and a flexible microfluidic sensor homogeneously integrated into the flexible circuit. The flexible sensor includes a flexible microfluidic structure, a first material, a second material, and an electrode arrangement. At least one of the first and second materials is a fluid. The structure defines at least one microfluidic chamber. The first and second materials are disposed in the chamber. The second material has a physical property and an electrical property different from the first material. The electrode arrangement includes at least one pair of electrodes spaced apart from each other with at least a portion of the at least one chamber located functionally directly therebetween such that at least one electronic property measured across the pair is based on a relationship between the second material and the electrode pair. The relationship is based on a physical condition of the microfluidic structure.

Abstract: A system and method for generating a tachometer signal from a vibration sensor is disclosed in which an approximately idealized band pass filter is used along with a fast Fourier transform (FFT) to create a sufficient analytic signal to derive the tachometer signal for a shaft or other rotating component. In addition, jitter in the generated tachometer signal, or any tachometer signal, can be reduced by using an approximately idealized low pass filter and then transforming the filtered signal using a real FFT. These processes can be performed using a smart vibration sensor, which facilitates improved vibration analysis on rotating equipment where in the past the addition of a tachometer would be prohibitive due to cost, weight, certification requirements, or physical impracticality.

Abstract: Apparatus and method for nano-identification a sample by measuring, with the use of evanescent waves, optical spectra of near-field interaction between the sample and optical nanoantenna oscillating at nano-distance above the sample and discriminating background backscattered radiation not sensitive to such near-field interaction. Discrimination may be effectuated by optical data acquisition at periodically repeated moments of nanoantenna oscillation without knowledge of distance separating nanoantenna and sample. Measurement includes chemical identification of sample on nano-scale, during which absolute value of phase corresponding to near-field radiation representing said interaction is measured directly, without offset. Calibration of apparatus and measurement is provided by performing, prior to sample measurement, a reference measurement of reference sample having known index of refraction.

Abstract: Systems and methods that enable both spectroscopy and rapid chemical and/or optical imaging using a broadband light source. Broadband light sources may be advantageous for spectroscopy as they simultaneously illuminate a sample with a plurality of wavelengths and use interferometric techniques to determine a material response as a function of wavelength (or equivalently wavenumber). Some embodiments may enable the same radiation sources to be used to efficiently map the spatial distribution of chemical species or optical property variations. This may be achieved via selection of specific optical phase delays within an interferometer that are selected to maximize the contrast between different absorption bands or resonances within the sample. By optimally selecting specific interferometer phases it may be possible to construct images that substantially represent the material response to a specific wavelength excitation, without the necessity to obtain entire spectra at each sample location.

Abstract: A die probe including a probe tip operably connected to a first surface of a thin film; a metal trace, wherein a first portion of the metal trace is operably connected to a second surface of the thin film, the second surface of the thin film opposite the first surface of the thin film; and an upper space transformer, wherein a second portion of the metal trace is operably connected to the upper space transformer, wherein a pressurized liquid and/or gas is configured to expand a space between the second surface of the thin film and the upper space transformer.

Abstract: A test probe tip can include a resistive element coupled with a tip component. The resistive element can include a resistive layer disposed on an exterior surface of a structural member of the resistive impedance element. In embodiments, the resistive element can be configured to form a structural component of the test probe tip without an insulating covering applied thereto. Additional embodiments may be described and/or claimed herein.

Abstract: A probe device of a vertical probe card is provided and includes a die assembly and at least one pin assembly. The die assembly includes a first die, a second die, and a middle die disposed between the first die and the second die. The at least one pin assembly has a first pin, a second pin, and at least one electrical connector. The at least one electrical connector is connected to the first pin and the second pin. The at least one pin assembly is electrically contacted with at least one contact pad of a device under test. The at least one contact pad leans against the at least one pin assembly, so that the at least one pin assembly generates a deformation in a longitudinal direction.

Abstract: A probe tip structure that decreases the accumulation rate of Sn particles to the probe tip and enables considerably more efficient and complete laser cleaning is disclosed. In an embodiment, the probe structure includes an array of probe tips, each probe tip having an inner core; an interfacial layer bonded to the inner core; and an outer layer bonded to the interfacial layer, wherein the outer layer is resistant to adherence of the solder of the ball grid array package.

Abstract: An arrangement for signal analysis provides at least one central data-processing unit and a screen unit connected to the at least one central data-processing unit, wherein the central data-processing unit calculates a spectrum and a spectrogram from a digitised signal. The at least one central data-processing unit is embodied in such a manner that it controls the screen unit in such a manner that the spectrogram of the digitised signal, the characteristic of the spectrum of the digitised signal and the characteristic of the digitised signal present in the time domain can be displayed together on the screen unit.

Abstract: A method and apparatus for providing variable analog to digital converter (ADC) resolution is described.

Abstract: An optical sensor assembly that senses current in a secondary electrical cable while sensing voltage in a primary electrical cable. The optical sensor assembly may include a sensor body, a concentrator core for measuring current. The concentrator core may be attached to a first end of the sensor body. The optical sensor assembly may include a plurality of extension arms that extend from the sensor body. The extension arms may include clamping devices on one end that are configured to attach to a first electrical cable. The concentrator core may be configured to at least partially surround a second electrical cable and sense the current from that second electrical cable.

Abstract: Systems and methods for calibrating a conducted electrical weapon (“CEW”) to provide a predetermined amount of current for each pulse of the stimulus signal. Providing the predetermined amount of current, close thereto, increases the effectiveness of the stimulus signal in impeding locomotion of a human or animal target. The calibration process enables a CEW to calibrate the amount of charge in a pulse of the stimulus signal in the environmental conditions where the tester operates and also in the field where the environmental conditions may be different from the environmental conditions during calibration.

Abstract: Systems and methods for calibrating a conducted electrical weapon (“CEW”) to provide a predetermined amount of current for each pulse of the stimulus signal. Providing the predetermined amount of current, close thereto, increases the effectiveness of the stimulus signal in impeding locomotion of a human or animal target. The calibration process enables a CEW to calibrate the amount of charge in a pulse of the stimulus signal in the environmental conditions where the tester operates and also in the field where the environmental conditions may be different from the environmental conditions during calibration.

Abstract: Systems and methods for calibrating a conducted electrical weapon (“CEW”) to provide a predetermined amount of current for each pulse of the stimulus signal. Providing the predetermined amount of current, close thereto, increases the effectiveness of the stimulus signal in impeding locomotion of a human or animal target. The calibration process enables a CEW to calibrate the amount of charge in a pulse of the stimulus signal in the environmental conditions where the tester operates and also in the field where the environmental conditions may be different from the environmental conditions during calibration.

Abstract: A current sensor includes a ferromagnetic core having a substantially central opening for receiving a current conductor and a gap. A detector of the current sensor includes at least one first magnetic field sensing element disposed in a first gap portion and configured to generate a respective first magnetic field signal in response to a first magnetic field having a first angle with respect to the at least one first magnetic field sensing element. The detector also includes at least one second magnetic field sensing element disposed in a second gap portion and configured to generate a respective second magnetic field signal in response to a second magnetic field having a second angle with respect to the at least one second magnetic field sensing element. The first and second magnetic fields are substantially equal in magnitude and the first and second angles are substantially opposite in polarity.