Patent Publication Number: US-2007095088-A1

Title: Body ventilation system and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application Ser. No. 60/728,679 entitled “WEARABLE COOLING SYSTEM,” filed on Oct. 20, 2005, which is hereby incorporated herein by reference in its entirety for all purposes. 
    
    
     FEDERALLY SPONSORED RESEARCH  
      Funding for portions of the present invention was obtained from the Government of the United States by virtue of Contract No. FA8650-04-C-6469 from the U.S. Department of the Air Force. The Government of the United States may have certain rights in and to the invention claimed herein. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      At least one embodiment of the present invention relates generally to devices and methods for personal comfort and, more particularly, to body ventilation systems and methods.  
      2. Discussion of Related Art  
      Metabolic processes, as well as external sources of heat, may lead to increased body core temperature. The natural cooling effect of ambient air flow over skin and clothes is typically sufficient to ensure personal comfort and to avoid heat stress. Prolonged exposure to inadequate heat dissipation and other harmful and/or extreme environmental conditions, however, can lead to fatigue, discomfort, impaired performance and serious health problems. Individuals who are required to wear substantially sealed garments associated with their job functions, for example, are especially at risk. In other cases, it may simply be desirable to enhance body ventilation, such as for therapeutic purposes.  
      Garment-based or otherwise wearable technology for improved body ventilation, particularly of the torso, has emerged. Liquid cooling is one known approach, generally involving tubing fashioned into a garment to circulate conditioned fluid, typically water. Gas ventilation techniques are also known which promote convective cooling by blowing a gas, typically air, towards a subject&#39;s body. Many wearable technologies rely upon substantial body coverage which may compound a wearer&#39;s thermal burden and resultant side effects.  
     BRIEF SUMMARY OF THE INVENTION  
      In accordance with one or more embodiments, the invention relates generally to an improved body ventilation system.  
      In accordance with one or more embodiments, the invention relates to a body ventilation system, comprising a permeable substrate, and a gas distributor comprising a network of gas flow elements disposed on the permeable substrate, and defining at least one channel in fluid communication with the gas flow elements.  
      In accordance with one or more embodiments, the invention relates to a body ventilation system, comprising a wicking layer proximate to the body, a gas distributor comprising a network of gas flow elements disposed on the wicking layer, the gas flow elements including a permeable base layer, a substantially incompressible spacer constructed and arranged to enable directional flow within the gas flow elements, and a substantially impermeable outer layer. The system may further include at least one channel defined by a perimeter of the gas distributor in fluid communication with the gas flow elements, and a source of gas fluidly connected to the gas distributor.  
      In accordance with one or more embodiments, the invention relates to a body ventilation system, comprising a permeable substrate, and a gas distributor comprising a network of gas flow elements constructed and arranged on the permeable substrate to provide airflow substantially parallel to a wearer&#39;s body, and defining at least one channel in fluid communication with the gas flow elements.  
      In accordance with one or more embodiments, the invention relates to a method of facilitating body ventilation for a class of users, comprising determining a ventilation requirement of the class of users, and selectively disposing a network of gas flow elements on a permeable substrate based on the determined requirement to direct gas flow substantially parallel to targeted regions of a user&#39;s body.  
      Other advantages, novel features and objects of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by like numeral. For purposes of clarity, not every component may be labeled in every drawing. Preferred, non-limiting embodiments of the present invention will be described with reference to the accompanying drawings, in which:  
       FIG. 1  illustrates a ventilation system in accordance with one or more embodiments of the present invention;  
       FIG. 2  illustrates gas flowing from a gas distribution element to a channel substantially parallel to a wearer&#39;s body in accordance with one or more embodiments of the present invention;  
       FIGS. 3A-3D  illustrate gas distributors with different gas flow element arrangements in accordance with various embodiments of the present invention; and  
       FIG. 4  illustrates a perspective view of a gas flow element applied to a substrate in accordance with one or more embodiments of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      This invention is not limited in its application to the details of construction and the arrangement of components as set forth in the following description or illustrated in the drawings. The invention is capable of embodiments and of being practiced or carried out in various ways beyond those exemplarily presented herein.  
      In accordance with one or more embodiments, the present invention relates generally to a body ventilation system. The system may be generally effective in providing ventilation for enhanced personal comfort. Various groups of individuals may have distinct ventilation requirements. In some circumstances, for example, individuals are required to wear protective garments or heavy gear that adds to their heat stress levels because of the nature of their activity and/or their environmental conditions. These individuals may benefit from a body ventilation system capable of providing a perceived cooling effect. Such persons include, but are not limited to, fighter pilots, aircraft ground crew, firemen, soldiers, athletes, race car drivers, “hazmat” operators, chemical plant operators, construction workers, and various medical personnel including surgical staff. Other groups of individuals may instead benefit from a body ventilation system capable of providing heated, filtered, or other types of conditioned ventilation. Yet other groups may benefit from an exhaust, rather than an infused, ventilation system. The systems presented herein are beneficially capable of customization to accommodate various ventilation requirements, as well as to target specific regions of a user&#39;s body.  
      The disclosed ventilation system may generally be a wearable system. The system may be modular, capable of insertion between garment layers or between a user&#39;s body and a garment layer. Alternatively, the ventilation system may be integrated into a garment or other wearable. The system is generally low bulk, designed to direct sufficient gas flow to where it is needed while attempting to minimize the thickness and/or number of layers worn by a user for bodily comfort. The system is also substantially flexible in nature. As used herein, “flexible” refers to an ability to substantially conform to a user&#39;s body and movement. An outer layer worn by the user may include an immersion suit or other protective ensemble.  
      In accordance with one or more embodiments, a ventilation system  100  generally includes a substrate  110  and a gas distributor  120  disposed on the substrate  110 , as illustrated in  FIG. 1 . Gas distributor  120 , discussed in greater detail below, is capable of providing a uniform distribution of gas flow relative to a user&#39;s body. The gas distributor  120  may be constructed and arranged to provide gas flow substantially parallel to a user&#39;s body. As used herein, “parallel to a user&#39;s body” refers generally to a path along a contour of the user&#39;s body. In at least one embodiment, system  100  including gas distributor  120  may promote both forced convection and evaporative cooling. Without wishing to be bound by any particular theory, flow of gas substantially parallel to the body may enhance moisture transport and provide discernible flow. Gas distributor  120  may be generally low profile and substantially incompressible to withstand the weight of outerwear and/or gear carriage and to avoid pinch points. As used herein, “incompressible” refers generally to resistance or unyielding to pressure and/or force.  
      During use, substrate  110  may be in direct contact with the user&#39;s body or with an under layer. The substrate  110  may be a gas permeable layer such that a user may discern gas flow through substrate  110 . As used herein, “permeable” generally refers to having pores or openings that permit liquids or gases to pass through. The substrate  110  may be a relatively thin layer to reduce bulk and/or heat stress. The substrate  110  may be made of a natural or synthetic material but should generally be compatible with intended applications for the ventilation system  100 . For example, in applications involving high temperatures or threat of fire, melting may be a concern and a substantially non-melt and/or non-drip material may be selected for substrate  110 . Thus, it may be desirable to select a natural fiber or avoid certain synthetic materials that may exacerbate burn wounds. As used herein, “non-melt” refers generally to having a sufficiently high melting point such that the material will not substantially change phases under anticipated environmental conditions. As used herein, “non-drip” refers generally to physical properties such that molten materials will tend not to form and/or fall in drops. Various tests and/or standards for material properties commonly known to those skilled in the art, such as the Thermal Stability Test, Vertical Flammability Test (ASTM D-6413), and NFPA 1951: Standard on Protective Ensemble for USAR Operations may be referenced in selecting the material.  
      In some embodiments, substrate  110  may be made of a wicking material for enhanced cooling and comfort. As used herein, “wicking” refers generally to an ability to promote absorption of moisture, such as perspiration off the skin or an undergarment. In some embodiments, the wicking material may be a natural fiber such as wool. In one preferred embodiment, the substrate  110  is made of a silk fabric. In another preferred embodiment, substrate  110  comprises lightweight wool. In other embodiments, the wicking material may be synthetic, such as a polypropylene material. In use, gas flow over the wicking material supplied by gas distributor  120  may dry the substrate  110 , effectively pulling more moisture off of the skin. Thus, according to one or more embodiments, the substrate  110  may enhance the rate and uniformity of evaporative cooling by diffusing moisture.  
      The substrate  110  coverage generally extends beyond the gas distributor  120  coverage. As illustrated, the substrate  110  may be a large sheet. Alternatively, the substrate  110  may be cropped closer to the outer perimeter of the gas distributor  120 . Substrate  110  may generally facilitate installation of the ventilation system  100  into a garment for ease of manufacture. In some embodiments, the substrate  110  may be a garment substrate. For example, the substrate  110  may be a body conformal T-shirt, skullcap, legging, vest, or helmet liner. In other embodiments, substrate  110  may instead be attached to a garment. Substrate  110 , in conjunction with gas distributor  120  discussed in greater detail immediately below, beneficially provides extensive gas flow area with minimal body coverage.  
      In accordance with one or more embodiments, gas distributor  120  generally includes a network of gas flow elements  130  disposed on substrate  110 , interspersed with at least one channel  140 . As used herein, “network” refers generally to a plurality or system of interconnected elements. The gas flow elements  130  may be disposed in a distributed array. A perimeter of the network of gas flow elements  130  defines the at least one channel  140 . The channel  140  comprises an open space or void over a surface of substrate  110  that is defined laterally by edges of the gas flow elements  130 . In use, the channel  140  may be defined orthogonally by an over garment or, instead, exposed to the atmosphere. In at least one embodiment, a channel  140  is in fluid communication with neighboring gas flow elements  130 . Gas flow elements  130  may include pores, slots, or other apertures to facilitate fluid communication with the channels  140 . In at least one embodiment, the apertures may be positioned on sides of the gas flow elements  130  to facilitate gas flow substantially parallel to a user&#39;s body. For example, as illustrated by block arrows in  FIG. 2 , gas flow may move through gas flow element  130  and exit through side apertures to channels  140  substantially parallel to a user&#39;s body. In accordance with one or more embodiments, channels  140  may generally provide a low bulk region of ventilation system  100  characterized by minimal body coverage due to the absence of gas flow elements  130 .  
      The gas permeable nature of substrate  110  may enhance perceived cooling by forced convection of substantially parallel airflow relative to a wearer&#39;s body in both channels  140  and gas flow elements  130 . Evaporative cooling may also be enhanced because substrate  110  provides a surface area to facilitate diffusion of absorbed perspiration. Evaporation may be promoted by the substantially parallel delivery of gas flow across a surface of substrate  110  in both channels  140  and gas flow elements  130 .  
      Various applications of the present invention may require different size, spacing, shape and arrangement of gas flow elements  130 . For example,  FIG. 3A , like  FIG. 1 , illustrates one preferred embodiment of a fan-shaped gas distributor  120  in which gas flow elements  130  have progressively widening cross-sections.  FIGS. 3B-3D  illustrate sample alternative embodiments of gas distributor  120 , although any shape may be implemented. Gas flow elements  130  may be selectively arranged based on particular ventilation requirements and to target specific regions of a user&#39;s body. The spacing and orientation of gas flow elements  130  should generally ensure that the cross sectional region of associated channels  140  is reasonably well maintained even under compression.  
      In accordance with one or more embodiments, the gas distributor  120  may generally provide directed gas distribution to promote even and substantially parallel gas flow relative to a user&#39;s body. Without wishing to be bound by any particular theory, a generally isotropic structure may cause gas flow paths within gas distributor  120  to short circuit, creating undesirable hot spots. Directional gas flow within gas distribution elements  130  may be facilitated by structural features of gas distribution elements  130  implemented to define a gas flow path.  
      For example, in at least one embodiment a spacer textile  180 , as illustrated in  FIG. 4 , may be incorporated in the design of gas distribution elements  130 . As used herein “spacer” refers generally to an ability to define or provide a gas flow path. In some embodiments, spacer textile  180  may generally include an array of coils enclosed in mesh. In other embodiments, spacer textile  180  may comprise architectural woven nylon defining anisotropic gas flow such that flow over a user&#39;s body is substantially uniform. As used herein, “anisotropic” refers generally to a direction dependent property. The spacer textile  180  may be oriented such that an axis of greater flow is along a length of gas flow element  130  to promote uniform flow substantially parallel to a user&#39;s body.  
      The spacer textile  180  should be substantially incompressible, able to withstand compression and to avoid pinch points along the gas flow path, as well as substantially gas and vapor permeable to generally facilitate ventilation. The spacer textile  180  may be flexible to allow ventilation system  100  to be conformable to a wearer&#39;s body. In at least one embodiment, spacer textile  180  may be generally low profile to reduce bulk. For example, in some embodiments, spacer textile  180  may be less than a half inch in thickness. The spacer textile  180  may be made of any material generally compatible with intended applications of ventilation system  100 . In some embodiments, spacer textile  180  may be polymer-based or natural fiber-based. In at least one embodiment, a substantially non-melt and/or non-drip material may be used for spacer textile  180 .  
      As illustrated, a membrane  170  may be fitted between substrate  110  and spacer textile  180 . Membrane  170  may be substantially permeable to facilitate absorption of perspiration and general ventilation. In other embodiments, membrane  170  may be substantially impermeable, for example, depending on the structure of spacer textile  180  at the interface with substrate  110 . A barrier membrane  190  may be applied over spacer textile  180 . Barrier membrane  190  may be substantially air impermeable to maintain supplied gas within gas flow element  130  to facilitate directional gas flow. In some embodiments, barrier membrane  190  may be vapor permeable to enable moisture transport. The barrier membrane  190  may contact an outer layer in use and should generally be high-strength, durable, and tear and/or snag resistant. In some embodiments, barrier membrane  190  may comprise an outer layer worn by the wearer. In at least one embodiment, barrier membrane  190  may be made of a commercially available material such as a Sympatex®, Kapton® FN film, or Gore-Tex® material.  
      Apart from the disclosed spacer textile  180 , embodiments of the present invention may include other structural features to facilitate directed gas flow. For example, discrete spacer elements may be included to define gas flow paths within gas flow elements  130 . The discrete spacer elements may be strategically positioned to define a desired gas flow pattern. In other embodiments, gas flow elements  130  may be selectively adhered to substrate  110  and/or barrier membrane  190  to define gas flow paths. An adhesive may be used in assembling gas flow elements  130 , and/or to attach gas flow elements  130  to substrate  110 . In some embodiments, the adhesive may be applied as a film or bead. The adhesive should be capable of creating a high strength bond without obstructing gas flow paths within gas flow elements  130 . The adhesive should generally be able to work on dissimilar materials and a resulting bond may be moisture resistant depending on the nature of the adhesive. In other embodiments, a welding technique, such as ultrasonic welding, may be used for adhesion. Sewing or other bonding techniques may also be used.  
      In accordance with one or more embodiments, ventilation system  100  may also include a manifold  160  and/or a gas duct  150 , as illustrated in  FIG. 1 . Air duct  150  and manifold  160  should generally be high strength, durable, flexible and substantially incompressible to avoid pinch points. Both should also be substantially air impermeable and sealable to avoid leaks. In some embodiments, a coated fabric such as a coated nylon or cotton may be used for gas duct  150  and manifold  160 . A membrane laminated fabric material may also be used.  
      In operation, gas may travel from a gas source (not shown) along gas duct  150  to enter manifold  160 . The gas source may include a gas supply and associated equipment such as fans, blowers, pumps and vacuums generally required to generate and maintain gas flow. In some embodiments, the gas source may be directly connected to manifold  160 . The gas may then be distributed among gas flow elements  130  from manifold  160 . The gas may travel laterally along a length of gas flow elements  130 , substantially parallel to the wearer&#39;s body, and exit to channels  140  along a perimeter of gas flow elements  130 , also substantially parallel to the wearer&#39;s body.  
      Beneficially, the gas source need not be embedded within system  100 . For flexibility in application, manifold  160  may be generally constructed and arranged to be connectable to various gas sources. In some embodiments, the gas source may be a portable or tethered supply, such as a blower, fan or compressed air canister. In other embodiments, the gas source may be an on-site gas supply. For example, the gas source may be installed at a construction site, athletic field, surgical theater, or be part of a vehicle air supply such as may be present in an airplane, race car or other mode of transport. The flow rate and system pressure should generally be sufficient to provide discernible gas flow and adequate to achieve enhanced personal comfort. The overall minimally restrictive design of ventilation system  100  may generally have low associated flow resistance, enabling use of a low pressure gas source and low system flow rates.  
      The gas from the gas source to be delivered via gas distributor  120  may be treated or conditioned for enhanced personal comfort. The gas may therefore be conditioned to facilitate heating, cooling, humidification, dehumidification, or circulation of filtered or otherwise treated gas. It is therefore contemplated that embodiments of the present invention may be used to treat conditions such as hypothermia and hyperthermia, as well as to facilitate therapeutic treatments including drug delivery and/or other transdermal techniques. In some embodiments, system  100  may also be configured to exhaust or extract gas from channels  140  via gas flow elements  130 , such as through reverse flow to the gas source by a vacuum pump. For example, system  100  may be configured to extract gas from channels  140  such that gas flows through gas flow elements  130  and exits gas manifold  160 .  
      As discussed above, the number, construction and arrangement of gas flow elements  130  can vary dramatically depending on an intended application. In at least one embodiment, a ventilation requirement for a class of users may first be determined. A network of gas flow elements  130  may then be selectively disposed on substrate  110  based on the determined requirement to direct gas flow substantially parallel to targeted regions of a user&#39;s body. For example, various embodiments of the present invention may target a user&#39;s torso, arms, legs, pelvis and/or head. In one embodiment, gas distributor  120  may have five or more gas flow elements  130  stemming from a single manifold  160 . Another embodiment may have a manifold  160  and a solitary gas flow element  130  stemming from gas duct  150  roughly every few inches.  
      It is envisioned that multiple ventilation systems  100  may be connected as part of a larger system. The multiple systems  100  may be arranged in series or parallel from a single or multiple source of gas. For example, a first system  100  targeting a wearer&#39;s torso may be fluidly connected to a second system  100  targeting a wearer&#39;s leg. In other embodiments, a single source of gas may provide gas flow to multiple users. The total flow impedance for each component branch should generally be the same at the point where branches join for even gas distribution. One or more sensors may be implemented to monitor characteristics of a user and/or operational parameter of system  100  as well. Such sensors may include, for example, temperature sensors, pressure sensors and flow meters.  
      Existing garments or personal ventilation systems may be retrofitted in accordance with one or more embodiments of the present invention.  
      The function and advantages of these and other embodiments of the invention can be further understood from the examples below, which illustrate the benefits and/or advantages of the system and method of the invention but do not exemplify the full scope of the invention.  
     EXAMPLE 1  
     Qualitative Performance of a Gas Ventilation Apparatus  
      A ventilation system, substantially in accordance with the system illustrated in  FIG. 1 , was worn by a human subject. The ventilation system was positioned against the subject&#39;s skin under a partially restrictive garment. A gas source was fluidly connected to the gas duct, providing roughly 10 cfm of ambient air to the subject. The human subject reported experiencing discernible gas flow against the subject&#39;s skin on both the front and back areas of the torso. An additional over garment was then donned by the subject to verify the performance of the ventilation system in the presence of further potential restrictions. Discernible flow was observed in this case, as well. The ventilation system was successful in resulting in a perceived cooling effect even under the constraints of a partially restrictive over garment.  
     EXAMPLE 2  
     Quantitative Performance of a Gas Ventilation Apparatus  
      The ventilation system used in Example 1 was subjected to Thermally Instrumented Manikin (TIM) testing to evaluate its cooling power. The ventilation system was tested in combination with a standard U.S. Army Chemically Protective Suit. Testing was carried out in a temperature and humidity controlled room with an ambient temperature set at 35° C. and relative humidity set at 50%. Details of the test methodology were as follows.  
      Evaluation of the cooling effectiveness of the ventilation system was conducted using a TIM test system. During the testing, environment temperature, skin temperature and power consumption were recorded.  
      The TIM test system consisted of a hollow aluminum manikin equipped with temperature sensors and electric heaters connected to a control system. The manikin was dressed in a garment incorporating the ventilation system to be tested and was placed in an appropriate environment. The control equipment controlled the heaters to maintain the skin of the manikin at a set temperature and measured the corresponding electric power required. This power was equivalent to the heat that escaped through the clothing due to the temperature difference across it, or the heat that was removed by the ventilation system.  
      The system comprised a TIM, a control module, environmental temperature and humidity sensors and cables connecting these components. The manikin was in a shape of human proportions to fit inside the test garment. The combinations of the aluminum shell of the manikin and the output of heaters inside it provided for an approximately uniform temperature over the manikin surface. This temperature was sensed by sensors embedded in the manikin&#39;s shell and was then passed to the control module.  
      The following clothing combination was used for testing. The manikin was first covered in a shirt with long sleeves and trousers assembled into a coverall (skin) made of a white 100% cotton textile. The first baseline test case (Baseline # 1 ) used an outer layer of a Chemical Protective Over-garment (pant and coat with hood) fitting directly over the coverall. The second baseline case (Baseline # 2 ) added the gas ventilation system, attached to a 50/50 cotton/poly T-shirt, between the coverall and the over-garment. The final test configuration was the same as Baseline # 2 , except with approximately 8 to 10 cfm of ambient air flowing through it.  
      Environmental sensors were suspended around the manikin to detect the environment temperature. The manikin temperature was set at 35° C. The ambient temperature of the chamber was also set at 35° C. The ambient relative humidity of the chamber was set at 50%. Water was sprayed onto the cotton garment at the beginning of each test run to simulate wetting by sweat. A warm-up period was provided to allow the manikin to reach the set temperature before going into a test period. The long-term power was monitored for all calculated sections until a steady state condition was reached, and the test was restarted.  
      The steady state power results of the thermal instrumented manikin with and without the gas ventilation system are shown in Table 1. The power results indicate the amount of power required to maintain the manikin temperature at 35° C.  
                           TABLE 1                                      Air Flow   Power (Watts)                                     Test   Description   (cfm)   Chest   Back   Total                                             Baseline #1   Protective suit, skin wet,   0   9.4   14.3   68.8           no air distribution system       Baseline #2   Protective suit, skin wet,   0   6.5   10.0   54.3           air distribution system,           no air       Test #1   Protective suit, skin wet,   8 to 10   20.1   26.5   101.0           air distribution system,           air on                  
 
      Table 1 illustrates the significant overall cooling power of the ventilation system of the present invention when energized with ambient air. In Test # 1 , with air being supplied by the distribution system, a total of 101.0 watts of power was required to maintain the manikin temperature at 35° C. This was significantly higher than the amount of power required during either of Baseline runs # 1  and # 2 . Thus, the ventilation system was successful in cooling the manikin. Furthermore, a comparison of the results of Baseline # 1  and Baseline # 2  demonstrates the minimal additional thermal stress added to the TIM by the ventilation system when the associated garment was not energized for cooling.  
      Other embodiments of the ventilation system of the present invention, and methods for its design and use, are envisioned beyond those exemplarily described herein.  
      As used herein, the term “plurality” refers to two or more items or components. The terms “comprising,” “including,”“carrying,” “having,” “containing,” and “involving,” whether in the written description or the claims and the like, are open-ended terms, i.e., to mean “including but not limited to.” Thus, the use of such terms is meant to encompass the items listed thereafter, and equivalents thereof, as well as additional items. Only the transitional phrases “consisting of” and “consisting essentially of,” are closed or semi-closed transitional phrases, respectively, with respect to the claims.  
      Use of ordinal terms such as “first,” “second,” “third,” and the like in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.  
      Those skilled in the art should appreciate that the parameters and configurations described herein are exemplary and that actual parameters and/or configurations will depend on the specific application in which the systems and techniques of the invention are used. Those skilled in the art should also recognize, or be able to ascertain, using no more than routine experimentation, equivalents to the specific embodiments of the invention. It is therefore to be understood that the embodiments described herein are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described.