Geospatial analysis of time to HIV diagnosis and adult HIV testing coverage highlights areas for intervention in the U.S. Southeast

Background

In the U.S., 44% of people with HIV (PWH) live in the Southeastern census region; many PWH remain undiagnosed. Novel strategies to inform testing outreach in rural states with dispersed HIV-epidemics are needed.

Methods

Alabama state public health HIV testing surveillance data from 2013-2017 were used to estimate time from infection to HIV diagnosis using CD4 T-cell depletion modeling, mapped to county. Diagnostic HIV tests performed 2013-2021 by commercial testing entities were used to estimate HIV tests per 100,000 adults (15-65-year-old), mapped to client ZIP code tabulation area (ZCTA). We then defined testing “cold spots”: those with <10% adults tested plus either (a) within or bordering one of the 13 counties with HIV prevalence greater than 400 cases per 100,000 population or (b) within a county with average time to diagnosis greater than the state average to inform testing outreach.

Results

Time to HIV diagnosis is a median of 3.7 (IQR 0-9.2) years across Alabama, with a range from 0.06-12.25 years. Approximately 63% of counties (N=42) have a longer time-to-diagnosis compared to national U.S. estimates. 643 ZCTAs tested 17.3% (IQR: 10.3%,25.0%) of the adult population from 2013-2017. To prioritize areas for testing outreach, we generated maps to describe 47 areas of HIV-testing cold spots at the ZCTA level.

Conclusions

Combining public health surveillance with commercial testing data provides a more nuanced understanding of HIV testing gaps in a state with a rural HIV epidemic and identifies areas to prioritize for testing outreach.

Optimal Synthesis of Robot Manipulators Based on Global Dynamic Parameters

The local nature of inertial, nonlinear, and coupling character istics of manipulators is an impediment to their optimal design. In this article, a method to represent and measure the global and posture-independent measures of inertia, coupling, and nonlinear forces is presented. A new concept, referred to as the global inertia ellipsoid, which represents the global iner tial characteristics of a manipulator, is introduced. The global inertia ellipsoid is obtained by considering a weighted distri bution of the end-effector position over the workspace of the manipulator. Based on this concept, four global parameters, representing the global nonlinear, coupling, and inertial char acteristics of the manipulator, are obtained. The number of global parameters does not change with the degrees of freedom or the complexity of the manipulator structure. A probabilistic or deterministic description of payload range can be included while designing the manipulator. Criteria for the optimal de sign of manipulators are presented in the form of an objective function of the global parameters. The method is illustrated by the design of a 2R manipulator, a 2R manipulator with given payload range, and a 3R manipulator. The extension of the concept of the global inertia ellipsoid to task placement and task planning is discussed.

An apparatus for measuring the load-displacement and load-dependent kinematic characteristics of articulating joints-application to the human ankle joint

An apparatus is described which is capable of measuring the load-displacement characteristics as well as determining the loci of centers of rotation of articulating joints. The apparatus employs a floating head which permits the axis of rotation to coincide with the position of minimum joint resistance, thus eliminating non-physiological rotations at the joint. The coupled loads are also measured, thus providing an accurate description of the joint structural characteristics. Data taken from a freshly amputated human ankle joint is presented.

An artificial compound eye for stereoendoscopy

A scanning endoscope has been designed with the ability to both project three-dimensional images and provide precise measurements of internal structures. This is beneficial for minimally invasive surgery, where surgeons suffer from a lack of depth perception, limited field of view, and the absence of a reference frame for dimensional measurements. Borrowing from the insect compound eye, the design uses an array of prisms, each facing a different direction but with overlapping fields of view. The prisms redirect their respective images normal to a fibre optic imaging plane and are individually controlled by electro-chromic shutters. The device thereby retains the ability to scan in multiple directions without mechanical parts and uses only a single camera. Comparison of the overlapping images with known prism positions allows for the calculation of absolute coordinates. Results from large-scale models show that the technology is plausible, and fabrication methods for a smaller device are discussed.

Evolution of a Non-Invasive Method for Providing Assistance to the Heart

The primary function of the ventricular chambers of the heart is to provide the proper volume of blood to the entire body that fulfills its energy requirements under a wide variety of normal and pathologic settings. If the ventricles are unable to perform this task properly, and the functions of the body deteriorates despite optimal medical management, mechanical methods are utilized to either complement or replace the pumping function of the cardiac ventricles. This presentation will describe the evolution of a non-invasive method of assisting the circulation called “counterpulsation,” and the current state of the development of an “External Left Ventricular Assist Device” (XLVAV). In this method, in the first part of the cardiac cycle, when the heart is relaxed, cardiac diastole, the device exerts a positive pressure external to the lower extremities. This increases coronary artery blood flow and cardiac output. Then when the ventricle contracts, cardiac systole, the device exerts a negative pressure, thus drawing blood away from the heart into the lower extremities, resulting in a reduction of the work and energy requirement of the left ventricle. Experimental and clinical data will be presented that describe the following successive stages of development: 1. The initial experience of Osborn in 1962 using a pressure suit and air actuation was tested in a canine model and in normal volunteers, but was not successful since sufficient pressure was not exerted on the vascular bed of the lower extremities. 2. The initial experimental experience of Birtwell and Soroff in a canine model in 1962 using water as the actuating medium. 3. The construction of a device by Birtwell with cuff-type actuators around the legs, thighs and buttocks that were inflated with water. The cuffs had rigid shells to allow pressure to be exerted to the limbs. The device was successful in increasing diastolic pressure and coronary blood flow and was used successfully in a multicenter study as an initial treatment of patients with acute myocardial infarctions. However, since the device could only apply positive pressure, it could not be used to reduce systolic pressure. 4. The device was then modified to also apply negative pressure during cardiac systole, a major step forward, and tested in a multicenter study in patients with cardiogenic shock following myocardial infacrtions with an impressive increase in the survival rate from 15% to 45%. However, the device presented logistical and patient movement problems. 5. The next evolution in the device design was the use of air to inflate the actuator cuffs. This represented a significant breakthrough, and has been successfully used in the treatment of angina pectoris by increasing coronary blood flow and the promotion or creation of collateral circulation in the myocardium. The serious shortcoming of this device is that is cannot produce negative pressure during cardiac systole, i.e., the only means of assisting the left ventricle in patients with Congestive Heart Failure. 6. The device to be described can apply negative as well as positive pressure to the lower extremities using air as the actuating medium. The device is mobile and compact, and should be effective in the treatment of patients with Congestive Heart Failure both in the hospital setting and in the home, Acute Myocardial Infarction as well as Angina Pectoris.

Development of an Automated Laser Debridement System for Cutaneous Injuries

The initial step in the repair of a thermal or chemical burn is wound debridement, the removal of the dead skin covering the burn. Afterwards, the exposed wound is covered with a viable biological dressing, the scabs re-form and the process must be repeated until the wound is fully healed. Of the various methods of wound debridement, surgical excision is the most popular. The process uses stainless steel cutting blades mounted on different types of handles which have built-in adjustments for controlling the depth of the excision. The main problems with this treatment method are excessive bleeding and lack of high-precision control of the cutting depth. Recent advances have been made in healing treatments for thermal and chemical burns using a variety of techniques to debride damaged tissue, including the use of medical lasers, such as CO2 and Er:YAG lasers. Excision using laser beams has been shown to be associated with significantly reduced morbidity, since the amount of blood lost during debridement is significantly reduced because the depth of treatment is more precise and the process has a cauterization cycle built-in. One drawback to the available laser systems is that they all require the surgeon to move a hand piece over the damaged area. This process requires great operator skill and is time consuming for an injury with a large surface area. Small hand held scanners attached to the end of articulated arms have mitigated this drawback to some extent, but the scanned areas are relatively small and the surgeon still needs to move the scanner head over larger injuries. This project describes the development of an automated, 3D vision guided laser debridement system with a large maximum working area for efficiently treating injuries with large areas or a multitude of smaller injuries distributed over a large area. This system is designed to be fail-safe, and performs precise debridement automatically and quickly with minimal surgeon involvement.

The contribution of the cruciate ligaments to the load-displacement characteristics of the human knee joint

Human knee specimens were subjected to anterior-posterior, medial-lateral, varus-valgus, and torsional displacement tests. Loads were recorded for the intact joint and for the joint with all soft tissues cut except for the cruciate ligaments. The effect of condylar interference was determined for anterior-posterior, medial-lateral, and torsional displacements. The variation in load with flexion angle was considerable for medial-lateral (0-90-deg flexion) displacements, and less for varus-valgus (0-45-deg flexion) displacements. The cruciates were found to carry almost the entire anterior-posterior load; they carried a significant percentage of the medial-lateral load which varied considerably with flexion angle. A small, but not insignificant percentage of the varus-valgus load was carried by the cruciates and the variations with flexion angle were small. In torsion, the cruciates resisted only internal rotation. In the tested displacement ranges, condylar interference had a small effect on the medial-lateral load but did not affect anterior-posterior or torsional loads.

Effect of Fixed Axes of Rotation on the Varus-Valgus and Torsional Load-Displacement Characteristics of the In-Vitro Human Knee

The effects of fixed axes of rotation on the varus-valgus and torsional load-displacement characteristics of the human knee have been determined. The location of the axes of varus-valgus and torsional rotations resulting in minimum resisting loads are also determined, and it is shown that they correspond to minimal coupled load levels. The coupled loads are seen to be sensitive to the location of the axis of rotation. The nonlinear load-displacement data is fitted with a four interval least-squares cubic spline with matching first and second derivatives at nodes. The data from two fresh human knees are presented.