Discriminating organic carbon from endokarstic moonmilk-type deposits by LIBS. The case of a natural carbonated Martian analogue

Moonmilk-type deposits exemplify carbonated Martian analogues existing in the subsurface of Earth, an endokarstic speleothem with a possible biochemical origin composed principally by carbonates, mainly huntite and dolomite. In this work, samples of moonmilk located in Nerja Cave (southern Spain) have been studied by LIBS with the aim of identifying carbon of biogenic origin by establishing a relationship between a molecular emission indicator, CN signal, and the organic carbon content. The characterization of this kind of carbonate deposit with a multiple mineralogical composition has been completed using scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray diffraction techniques for qualitative and semi-quantitative analysis. The information attained from LIBS regarding energy thresholds and time-resolved kinetics of CN emissions provides useful insight into the identification of different molecular emitters, namely organic and inorganic CN, depending on the laser irradiance and time settings conditions. These promising results are of application in the search and identification of biosignatures in upcoming planetary missions with astrobiological purposes.

Coronavirus pandemic: An opportunity to study the anthropogenic impact on micro-climate conditions and CaCO3 crystal morphology in the Nerja Cave (SE Spain)

Following the declaration of the COVID-19 pandemic, the Spanish Government restricted non-essential movements of all citizens and closed all public spaces, such as the Nerja Cave, until May 31, 2020. This particular condition of the closure of the cave provided a unique opportunity to study the micro-climate conditions and carbonate precipitation in this tourist cave without the presence of visitors. Our results show the significant effect of visitors on the air isotopic signature of the cave and on the genesis of the extensive dissolution features affecting the carbonate crystals formed in the tourist sector of the cave, alerting us to the possible corrosion of the speleothems located there. The movement of visitors within the cave also favours the mobilisation of aerial fungi and bacterial spores and their subsequent sedimentation simultaneously with the abiotic precipitation of carbonates from the drip water. The traces of these biotic elements could be the origin of the micro-perforations previously described in the carbonate crystals formed in the tourist galleries of the cave, but they are subsequently enlarged due to abiotic dissolution of the carbonates through these weaker zones.

Application of hydrochemical and multi-isotopic (87Sr/86Sr, δ13C-DIC, δ2H-H2O, δ18O-H2O) tools to determine contamination sources and processes in the Guadalhorce River Basin, southern Spain

The integrated use of multi-isotopic (⁸⁷Sr/⁸⁶Sr, δ¹³C-DIC, δ²H-H₂O, δ¹⁸O-H₂O) and hydrochemical data was applied in the highly anthropized Guadalhorce river basin, southern Spain, to improve the knowledge about water contamination sources and processes and to achieve improved water resource management. The results obtained highlight the importance of the use of isotopes as tracers of pollutants. DIC, δ²H-H₂O, δ¹⁸O-H₂O and δ¹³C-DIC allowed differentiating two water recharge end members: direct rainwater, infiltrated into the upper and lower detritic aquifers of the sub-basins, and the Guadalhorce dam system, which act as a source in some groundwater and surface waters of the lower sub-basin. ⁸⁷Sr/⁸⁶Sr data supported the existing conclusions in relation to pollution sources in the study area. The Triassic basement (evaporites) of the carbonate and detritic aquifers of the basin generally controls the natural ⁸⁷Sr/⁸⁶Sr composition in waters of the upper sub-basin. Only one groundwater sample reflects the influence of a human organic source (sewage) in its composition. On the other hand, mixing of human inorganic (fertilizers and detergents) strontium sources is required to explain the ⁸⁷Sr/⁸⁶Sr contents of the lower sub-basin waters. Discriminating the use of domestic detergents as another anthropogenic source of strontium and sulphate in waters is a novel finding in this research. The conclusions reached can be extrapolated to other anthropized basins.

Quantifying warfighter performance during a bounding rush (prone-sprinting-prone) maneuver

A single sacrum mounted inertial measurement unit (IMU) was employed to analyze warfighter performance on a bounding rush (prone-sprinting-prone) task. Thirty-nine participants (23M/16F) performed a bounding rush task consisting of four bounding rush cycles. The sacrum mounted IMU recorded angular velocity and acceleration data were used to provide estimates of sacral velocity and position. Individual rush cycles were parsed into three principal movement phases; namely, the get up, sprint, and get down phases. The timing of each phase was analyzed, averaged for each participant, and compared to the overall rush cycle time using regression analysis. A cluster analysis further reveals differences between high and low performers. Get down time was most predictive of bounding rush performance (R² = 0.75) followed by get up time (R² = 0.58) and sprint time (R² = 0.40). Comparing high and low performers, the get down time exhibited nearly twice the effect on mean rush cycle time compared to get up time (effect size of -2.61 to -1.46, respectively). Overall, this IMU-based method reveals key features of the bounding rush that govern performance. Consequently, this objective method may support future training regimens and performance standards for military recruits, and parallel applications for athletes.

Coupling air temperature records and gravimetric data to interpret ventilation patterns in a Mediterranean karstic system (Nerja-Pintada caves, southern Spain)

Microclimate and geophysical studies are commonly applied to the characterization of karst systems although they are usually used separately. The main purpose of this manuscript is to show how the analysis of the data from both these research methods is a useful tool in the characterization of karst systems and we present the analysis of a specific case study: the Nerja- Pintada caves system. The joint analysis of the Nerja Cave and external air data (mainly temperatures) and the pre-existing gravimetric data of its surroundings (residual gravity anomaly map) have allowed us: 1) to postulate the existence of an unknown great cavity located near to the Nerja Cave and with direct influence in its ventilation and 2) to propose a new model of the Nerja-Pintada caves ventilation based on the changing connection between a "main cavity" system (Nerja Cave), with basically a transmissive function of airflows and an "annex cavities" sub-system, with different functioning as far as the airflow is concerned: transmissive in the case of Pintada Cave and capacitive in the case of the geophysically-located cave.

CAPTURING REAL-WORLD LOSSES OF BALANCE AND RECOVERY RESPONSES IN OLDER ADULTS AT RISK FOR FALLS

Losses of balance (LOBs) such as trips can lead to falls in older adults; what actually happens during real-world LOBs is unclear. With 4 wearable inertial measurement units (IMUs), we recorded feet, trunk and wrist movements over 2 weeks. Using a wrist voice recorder to report the LOBs, we applied our IMU processing algorithms and reconstructed the full body LOB and recovery motions. We recruited 7 at-risk older adults (M=76 yrs) who reported 114 LOBs of which we reconstructed over 90%. Using a rating system, 52% of the LOBs involved a significant trip, stumble, recovery step, and/or large trunk motion. 25% involved double or stutter steps and smaller trunk motions. The other 23% had less striking associated motions. These data suggest that most, but not all, self-reported real world LOBs involve substantial postural destabilization and near falls. Analyses of the voice-recorded context under which the LOBs occurred are ongoing.

Comparing head impact kinematics simultaneously measured using 6 different sensors in a human cadaver model

Objective

To compare head kinematics measurements obtained from 6 different head impact sensors utilizing different methods of sensor-to-head fixation.

Design

Free-drop impacts (total n = 54) were performed at 3.5 and 5.5 m/s onto to the front, back, side, and top of 2 elderly human cadaveric head-neck specimens: a helmeted (Riddell Revolution Speed) male specimen was dropped onto a NOCSAE testing pad; an un-helmeted female specimen was dropped onto a framed sample of field turf. The specimens were instrumented with an intracranial reference sensor surgically mounted at the approximate head center-of-mass by a rigidly-fixed custom standoff pad, an intra-oral test sensor rigidly fixed to the upper teeth/hard palate by a custom orthodontic appliance, and 4 commercially available head impact sensing systems: X-Patch, Vector mouth guard, HITS (helmeted condition only), and G-Force Tracker (affixed to helmet interior or head band depending on helmet status). Peak linear and rotational head accelerations (PLA and PRA) were compared between each sensor and the intracranial reference sensor using intraclass correlation coefficients (ICC [2, 1]).

Results

Agreement with reference PLA and PRA values differed between sensors, with the greatest agreement observed for the rigidly affixed intraoral sensor (ICC = 0.921, PLA; ICC = 0.810, PRA). Agreement for PLA and PRA, respectively, was: for X-Patch, ICC = 0.638, ICC = 0.155; for Vector mouth guard, ICC = 0.775, ICC = 0.480; for HITS, ICC = 0.662 (PLA only); for G-Force Tracker, ICC = 0.364 (PLA only).

Discussion

Head kinematics measurements during free-drop testing differed among sensors using different approaches of fixation to the head. There was greater agreement with intracranial reference PLA and PRA values for a rigidly affixed intraoral sensor utilizing an orthodontic appliance than for commercially available sensors incorporated into athletic equipment or otherwise non-rigidly affixed to the head. Measurement error attributable to non-rigid sensor-head coupling could potentially be reduced by incorporating an impact sensor into an orthodontic appliance in future research.

Highlighting the importance of transitional ventilation regimes in the management of Mediterranean show caves (Nerja-Pintada system, southern Spain)

This study shows the utilization of the air CO₂ exhaled by a very high number of visitors in the Nerja Cave as both a tracer and an additional tool to precisely evaluate the air circulation through the entire karst system, which includes non-touristic passages, originally free of anthropogenic CO₂. The analysis of the temporal - spatial evolution of the CO₂ content and other monitoring data measured from January 2015 to December 2016 in the Nerja-Pintada system, including air microbiological controls, has allowed us to define a new general ventilation model, of great interest for the conservation of the subterranean environment. During the annual cycle four different ventilation regimes and two ventilation modes (UAF-mode and DAF-mode) exist which determine the significance of the anthropogenic impact within the caves. During the winter regime, the strong ventilation regime and the airflow directions from the lowest to the highest entrance (UAF-mode) contribute to the rapid elimination of anthropogenic CO₂, and this affects the whole karstic system. During the summer regime the DAF-mode ventilation (with airflows from the highest to the lowest entrances) is activated. Although the number of visitors is maximum and the natural ventilation of the karstic system is the lowest of the annual cycle, the anthropogenic impact only affects the Tourist Galleries. The transitional ventilation regimes -spring and autumn- are the most complex of the annual cycle, with changing air-flow directions (from UAF-mode to DAF-mode and vice versa) at diurnal and poly diurnal scale, which conditions the range of the anthropogenic impact in each sector of the karst system. The activation of the DAF-mode has been observed when the temperature difference between the external and air cave is higher than 5°C.

Load-embedded inertial measurement unit reveals lifting performance

Manual lifting of loads arises in many occupations as well as in activities of daily living. Prior studies explore lifting biomechanics and conditions implicated in lifting-induced injuries through laboratory-based experimental methods. This study introduces a new measurement method using load-embedded inertial measurement units (IMUs) to evaluate lifting tasks in varied environments outside of the laboratory. An example vertical load lifting task is considered that is included in an outdoor obstacle course. The IMU data, in the form of the load acceleration and angular velocity, is used to estimate load vertical velocity and three lifting performance metrics: the lifting time (speed), power, and motion smoothness. Large qualitative differences in these parameters distinguish exemplar high and low performance trials. These differences are further supported by subsequent statistical analyses of twenty three trials (including a total of 115 total lift/lower cycles) from fourteen healthy participants. Results reveal that lifting time is strongly correlated with lifting power (as expected) but also correlated with motion smoothness. Thus, participants who lift rapidly do so with significantly greater power using motions that minimize motion jerk.

Low-back electromyography (EMG) data-driven load classification for dynamic lifting tasks

OBJECTIVE

Numerous devices have been designed to support the back during lifting tasks. To improve the utility of such devices, this research explores the use of preparatory muscle activity to classify muscle loading and initiate appropriate device activation. The goal of this study was to determine the earliest time window that enabled accurate load classification during a dynamic lifting task.

METHODS

Nine subjects performed thirty symmetrical lifts, split evenly across three weight conditions (no-weight, 10-lbs and 24-lbs), while low-back muscle activity data was collected. Seven descriptive statistics features were extracted from 100 ms windows of data. A multinomial logistic regression (MLR) classifier was trained and tested, employing leave-one subject out cross-validation, to classify lifted load values. Dimensionality reduction was achieved through feature cross-correlation analysis and greedy feedforward selection. The time of full load support by the subject was defined as load-onset.

RESULTS

Regions of highest average classification accuracy started at 200 ms before until 200 ms after load-onset with average accuracies ranging from 80% (±10%) to 81% (±7%). The average recall for each class ranged from 69-92%.

CONCLUSION

These inter-subject classification results indicate that preparatory muscle activity can be leveraged to identify the intent to lift a weight up to 100 ms prior to load-onset. The high accuracies shown indicate the potential to utilize intent classification for assistive device applications.

SIGNIFICANCE

Active assistive devices, e.g. exoskeletons, could prevent back injury by off-loading low-back muscles. Early intent classification allows more time for actuators to respond and integrate seamlessly with the user.

Quantifying performance on an outdoor agility drill using foot-mounted inertial measurement units

Running agility is required for many sports and other physical tasks that demand rapid changes in body direction. Quantifying agility skill remains a challenge because measuring rapid changes of direction and quantifying agility skill from those measurements are difficult to do in ways that replicate real task/game play situations. The objectives of this study were to define and to measure agility performance for a (five-cone) agility drill used within a military obstacle course using data harvested from two foot-mounted inertial measurement units (IMUs). Thirty-two recreational athletes ran an agility drill while wearing two IMUs secured to the tops of their athletic shoes. The recorded acceleration and angular rates yield estimates of the trajectories, velocities and accelerations of both feet as well as an estimate of the horizontal velocity of the body mass center. Four agility performance metrics were proposed and studied including: 1) agility drill time, 2) horizontal body speed, 3) foot trajectory turning radius, and 4) tangential body acceleration. Additionally, the average horizontal ground reaction during each footfall was estimated. We hypothesized that shorter agility drill performance time would be observed with small turning radii and large tangential acceleration ranges and body speeds. Kruskal-Wallis and mean rank post-hoc statistical analyses revealed that shorter agility drill performance times were observed with smaller turning radii and larger tangential acceleration ranges and body speeds, as hypothesized. Moreover, measurements revealed the strategies that distinguish high versus low performers. Relative to low performers, high performers used sharper turns, larger changes in body speed (larger tangential acceleration ranges), and shorter duration footfalls that generated larger horizontal ground reactions during the turn phases. Overall, this study advances the use of foot-mounted IMUs to quantify agility performance in contextually-relevant settings (e.g., field of play, training facilities, obstacle courses, etc.).

Mobile platform for motion capture of locomotion over long distances

Motion capture is usually performed on only a few steps of over-ground locomotion, limited by the finite sensing volume of most capture systems. This makes it difficult to evaluate walking over longer distances, or in a natural environment outside the laboratory. Here we show that motion capture may be performed relative to a mobile platform, such as a wheeled cart that is moved with the walking subject. To determine the person's absolute displacement in space, the cart's own motion must be localized. We present three localization methods and evaluate their performance. The first detects cart motion solely from the relative motion of the subject's feet during walking. The others use sensed motion of the cart's wheels to perform odometry, with and without an additional gyroscope to enhance sensitivity to turning about the vertical axis. We show that such methods are practical to implement, and with present-day sensors can yield accuracy of better than 1% over arbitrary distances.

Plasma concentrations of beta-endorphin in smokers who consume different numbers of cigarettes per day

The harmful effects of smoking on health have been widely documented, although it is as yet unclear whether tobacco dependence is only psychological in nature, or both psychological and physical. We studied plasma concentrations of beta-endorphin, cortisol, and adrenocorticotropic hormone (ACTH) in healthy persons who consumed different numbers of cigarettes per day, and compared the findings with those in a control group of nonsmokers. Beta-endorphin levels were significantly higher than in controls only in persons who smoked fewer than 10 cigarettes per day. Cortisol levels were significantly higher in smokers who consumed more than 20 cigarettes per day. There were no significant differences between any of the groups in plasma ACTH concentrations.

Role of the cytoskeleton in endocytosis of the yeast maltose transporter

Certain components of the cytoskeleton play a role in yeast fluid-phase endocytosis as well as in endocytosis of the alpha-factor when this pheromone is bound to its 7-transmembrane segment receptor. The yeast maltose transporter is a 12-transmembrane segment protein that, under certain physiological conditions, is degraded in the vacuole after internalization by endocytosis. In this work, the possible role of the cytoskeleton in endocytosis of this transporter has been investigated. Using mutants defective in beta-tubulin, actin and the actin-binding proteins Sac6 and Abp85. as well as nocodazole, which inhibits formation of microtubules, we have shown that actin microfilaments are involved in endocytosis of the maltose transporter whereas microtubules are not.

Clinical study of comparative plaque removal performance of two manual toothbrushes

A clinical study was performed to evaluate and compare plaque removal performance of the two commercially available products; the Colgate Precision Full Head Soft toothbrush and Reach Full Head soft toothbrush. Twenty high school students, male and female subjects participated, each refraining from toothbrushing for 24 hours. Plaque was scored according to the Personal Hygiene Performance (PHP) Index of Podshadley and Haley, as modified by Martens and Meskin. Following screening, the subjects were divided into two balanced groups on the basis of initial plaque scores. At Visit 1, each group having refrained from toothbrushing for 24 hours, was evaluated for plaque before brushing for 60 seconds with the assigned toothbrush, after which plaque was again scored. At Visit 2, one week later, the same procedure was followed. Subjects were instructed to resume their normal routine and return to the clinical site for Visit 2. On completion of the study, the data collected were subjected to statistical analysis which indicated that the Colgate Precision Full Head soft toothbrush removed significantly more plaque than Reach Full Head soft toothbrush.

Early experience with Walsh technique of radical retropubic prostatectomy

We analyzed the operative experience and postoperative and late complications of pelvic lymphadenectomy and radical retropubic prostatectomy in 27 consecutive cases in which the modifications of prostatectomy described by Walsh were employed, and compared the results with those of 29 cases performed in the preceding three years when the Campbell technique of prostatectomy was employed. The mean operative time, mean blood loss, and incidences of early postoperative complications and incontinence were less for patients treated with the Walsh technique than with the Campbell technique. After surgery 85 per cent of evaluable patients remained potent with the Walsh technique compared with 16 per cent of patients treated with the Campbell technique. Although other factors besides operative approach may have biased our results, we are persuaded that the innovations of radical retropubic prostatectomy detailed by Walsh constitute important advances in surgical technique, and we now use this procedure in all suitable patients electing treatment by radical prostatectomy for localized prostatic cancer.

Apalcillin treatment of complicated urinary tract infections

In an open, prospective clinical trial, we evaluated the safety and efficacy of apalcillin in the treatment of complicated urinary tract infection. 21 hospitalized adult patients received apalcillin 2 g IV Q8-12 h for 5-17 days. There were 8 upper tract and 13 lower tract infections. Of 25 functional or anatomic abnormalities of the GU tract among these patients, 9 (36%) were corrected during the study period. Effectiveness of apalcillin was determined by clinical and bacteriologic response. 16 (76.2%) patients had clinical cures, 4 (19.8%) had clinical improvement, and 1 (4.8%) had clinical failure. Based on 26 pretreatment isolates, there were 16 (61.5%) bacteriologic cures and 10 (38.5%) failures. Failures were due to 6 (23.1%) relapses, 2 (7.7%) superinfections, and 2 (7.7%) relapses with superinfection. Adverse reactions were mild, transient, and did not require discontinuation of treatment. Apalcillin appears to be a safe, although marginally effective single agent antibiotic for the treatment of complicated urinary tract infections.

Lymphocele formation after extraperitoneal pelvic lymphadenectomy: possible predisposing factors

A retrospective review of 61 patients undergoing pelvic lymphadenectomy was performed to assess possible predisposing factors for lymphocele development. The procedure was done to facilitate staging of prostatic carcinoma in all of the patients. The complication occurred in 9 patients (14.8 per cent). Analysis revealed a statistically significantly higher incidence of lymphoceles in patients without drainage (p less than 0.05) and in patients whose lymph nodes had no metastatic disease (p less than 0.025). Furthermore, 9 patients (without drainage and with nodes that were free of tumor but who received mini-dose heparin therapy) as a subgroup had the highest incidence of lymphocele formation. Although these individual factors have been attributed to this complication after lymphadenectomy they may act synergistically.

Comparison of leuprolide and diethylstilbestrol for stage D2 adenocarcinoma of prostate

In a controlled, prospective, randomized clinical trial, we evaluated the safety and efficacy of leuprolide, a superactive analog of luteinizing hormone releasing hormone, given in a single subcutaneous injection dose of 1 mg per day, versus diethylstilbestrol (DES) 3 mg per day by mouth in patients with previously untreated Stage D2 prostatic adenocarcinoma. Eleven leuprolide patients and 10 DES patients were evaluated for therapeutic response. Eighty per cent of patients in each group experienced subjective improvement in bone pain and urinary obstructive signs and symptoms. Although the pooled percentages of complete, partial, and stable objective responses were greater for the leuprolide group than the DES group, the sums of the percentages of complete and partial objective responses were comparable for both treatment groups during the first forty-eight and sixty weeks of the study, respectively. In addition, patients not responding to leuprolide generally experienced no benefit with crossover to DES, and vice versa. Serious adverse reactions were more common in the DES group and included fatal myocardial infarction, arrhythmia, deep venous thrombosis, and gynecomastia. Vasomotor flushing, disease flare, and injection site irritation occurred most often in leuprolide patients, but did not require modification or discontinuation of treatment.

Comparative efficacy of piperacillin versus carbenicillin for complicated urinary tract infections

In this controlled, randomized clinical trial we compared piperacillin and carbenicillin in the treatment of complicated urinary tract infections. 24 patients received piperacillin 150 mg/kg/day for 7.2 +/- 2.75 days and 17 patients received carbenicillin 200 mg/kg/day for 7.5 +/- 2.90 days. Patients were evaluated for clinical and bacteriologic responses and tolerance to therapy. Although the clinical cure rate significantly favored carbenicillin treatment (p less than 0.01), the sum of the percentages of cases with clinical cure and clinical improvement were similar between groups: 91.6% for piperacillin and 88.2% for carbenicillin. The bacteriologic cure rates for piperacillin and carbenicillin patients (54.1 and 47.0%, respectively) were not significantly different (p greater than 0.05). The low cure rates in our study were probably the result of uncorrected/uncorrectable genitourinary tract abnormalities. Superinfections developed in 12.5 and 17.6% of piperacillin and carbenicillin patients, respectively, and were due to Klebsiella pneumonia, Proteus mirabilis, Citrobacter diversus, and Pseudomonas aeruginosa. Overall, side effects were mild, reversible, and did not require discontinuation of treatment. However, carbenicillin caused elevations in liver enzymes more frequently than piperacillin (p less than 0.05). Based on our data, we recommend reserving piperacillin monotherapy for patients who are poor candidates for aminoglycosides, or are on severe sodium restriction, and have serious complicated urinary tract infections due to susceptible organisms. We do not recommend piperacillin alone for empiric treatment of complicated urinary tract infections.

Partial cystectomy: can it be incorporated into integrated therapy program?

A retrospective study of 23 partial cystectomies for bladder cancer performed during a twelve-year period revealed no operative deaths and a low morbidity. Bladder capacity was little affected by the use of preoperative radiotherapy, and complications were minimal. The results suggest that protracted radiotherapy can be used preoperatively without adversely influencing operative complications.

Preliminary report comparing piperacillin and carbenicillin for complicated urinary tract infections

Piperacillin is a new semisynthetic penicillin with a broad spectrum of in vitro activity against common gram-negative urinary tract pathogens. We compared the efficacy and safety of piperacillin versus carbenicillin in patients with complicated urinary tract infection. A total of 56 adult patients (mean age 55 years) in stable medical condition with 1 or more structural genitourinary abnormalities entered the study. Of these patients 27 were evaluated for antibiotic efficacy. There were 20 lower tract and 7 upper tract infections, of which 17 were acute and 10 were chronic. Patients were randomized into 2 groups: 17 patients with 18 organisms received single agent treatment with 181 mg. per kg. intravenous piperacillin daily for 6 days and 10 patients with 11 organisms received 270 mg. per kg. intravenous carbenicillin daily for 6 days. Infecting organisms were Escherichia coli 45 per cent, Proteus mirabilis 14 per cent, Klebsiella pneumoniae 14 per cent. Enterobacter species 10 per cent, Pseudomonas aeruginosa 7 per cent and so forth. Antimicrobial susceptibility assessed by measurement of minimal inhibitory concentration and disk diffusion zone size demonstrated superior activity of piperacillin over carbenicillin for most micro-organisms tested. All patients responded clinically. The bacteriologic cure rate was 72 per cent at 5 to 9 days after therapy in both groups. Three patients who received piperacillin had urosepsis and were cured. No resistance emerged during therapy. Superinfections developed in 5 patients on carbenicillin (50 per cent) and in 4 patients on piperacillin (24 per cent), and none was resistant to piperacillin. Superinfections were attributed to catheterization and structural genitourinary abnormalities. The over-all incidence of adverse effects in patients on piperacillin was less than that of those on carbenicillin, 31 and 51 per cent respectively. Side effects in both groups were mild and did not require discontinuation of therapy. There were no significant alterations in fluid and electrolyte balance, or hematologic or renal function.