摘要:
Provided are methods and compositions for regulating gene expression in a cell. The invention provides recombinant genetic toggle switches which contain a first constitutive promoter-regulatory gene operon and a second constitutive promoter-regulatory gene operon. Expression of the regulatory gene from the first operon inhibits expression from the promoter in the second operon, and expression of the regulatory gene from the second operon inhibits expression from the promoter in the first operon. By use of the toggle switch and various switching agents it is possible to reversibly switch the expression of a gene of interest between a stable “on” state and stable “off” state or vice versa via transient exposure to a switching agent.
摘要:
Provided are methods and compositions for regulating gene expression in a cell. The invention provides recombinant adjustable-threshold switches which contain a first inducible promoter-regulatory gene operon and a second constitutive promoter-regulatory gene operon. A threshold amount of activating agent is required to switch the inducible promoter “on” and the constitutive promoter “off”. An adjustable-threshold switch is useful to reversibly switch the expression of a gene of interest between a stable “on” state and stable “off” state in response to an activating agent at or above a threshold concentration.
摘要:
The present invention provides methods and accompanying computer-based systems and computer-executable code stored on a computer-readable medium for constructing a model of a biological network. The invention further provides methods for performing sensitivity analysis on a biological network and for identifying major regulators of species in the network and of the network as a whole. In addition, the invention provides methods for identifying targets of a perturbation such as that resulting from exposure to a compound or an environmental change. The invention further provides methods for identifying phenotypic mediators that contribute to differences in phenotypes of biological systems.
摘要:
Provided are methods and compositions for regulating gene expression in a cell. The invention provides recombinant multi-state genetic oscillators containing an adjustable-threshold genetic switch that is periodically activated by an oscillating amount of an activator agent. The activating agent is a gene product expressed from a promoter regulated by the adjustable-threshold switch and thus forms a feedback loop that causes periodic switching of the adjustable-threshold switch between an “on” state and an “off” state. Multi-state genetic oscillators are useful to express one or more genes of interest in a periodic manner without requiring a periodic application of an external activating agent.
摘要:
An apparatus for head mounting gear for hands free operation includes a headband and adjustable mounting structure wherein gear such as binoculars and range finders may be selectively mounted, and such gear once mounted may be conveniently raised to a storage position or placed in a use position. The structure includes a quick release mechanism which enables quick and easy interchange between various gear. The headband is preferably comprised of an encircling band and a band that goes over the top of the head. The mounting support structure has adjustments for length from the eyes and height. It is further adjustable into multiple use positions and vertical angle line of sight adjustment.
摘要:
A diesel exhaust gas aftertreatment system (10) is provided to treat the exhaust (12) from a diesel combustion process (14), such as a diesel compression engine (16). The system (10) includes a burner (18) that selectively supplies the exhaust (12) at an elevated temperature to the rest of the system (10), a diesel particulate filter (20) connected downstream from the burner (18) to receive the exhaust (12) therefrom, and a NOx reducing device (22) connected downstream from the filter (20) to receive the exhaust therefrom.
摘要:
A vehicle exhaust system for an engine having a plurality of combustion chambers includes a first emission treatment device, a second emission treatment device and a housing defining a first exhaust passageway in fluid communication with the combustion chambers and containing the first emission treatment device. A second parallel exhaust passageway is in fluid communication with the combustion chambers and contains the second emission treatment device. The first and second passageways share a common wall having a serpentine shape such that the cross-sectional area of the passageways varies along a direction of exhaust flow. The first emission treatment device is positioned at a location of increased cross-sectional area in the first passageway and the second emission treatment device is positioned at an axially offset location of increased cross-sectional area in the second passageway.
摘要:
An exhaust system for an engine having a plurality of combustion chambers includes a housing containing a first array of parallel positioned emission treatment devices and a second array of parallel positioned emission treatment devices axially spaced apart from one another. A first exhaust passageway is in fluid communication with the combustion chambers and contains the first array of emission treatment devices. A second and separate exhaust passageway is in fluid communication with the combustion chambers and contains the second array of emission treatment devices. A first valve restricts the exhaust flow through the first exhaust passageway. A second valve restricts the exhaust flow through the second exhaust passageway.
摘要:
The present invention provides methods and accompanying computer-based systems and computer-executable code stored on a computer-readable medium for constructing a model of a biological network. The invention further provides methods for performing sensitivity analysis on a biological network and for identifying major regulators of species in the network and of the network as a whole. In addition, the invention provides methods for identifying targets of a perturbation such as that resulting from exposure to a compound or an environmental change. The invention further provides methods for identifying phenotypic mediators that contribute to differences in phenotypes of biological systems.
摘要:
The present invention provides methods and accompanying computer-based systems and computer-executable code stored on a computer-readable medium for constructing a model of a biological network. The invention further provides methods for performing sensitivity analysis on a biological network and for identifying major regulators of species in the network and of the network as a whole. In addition, the invention provides methods for identifying targets of a perturbation such as that resulting from exposure to a compound or an environmental change. The invention further provides methods for identifying phenotypic mediators that contribute to differences in phenotypes of biological systems.